Study Set Flashcards
order of ionic loss of a rock as it weathers
CO32-, Mg2+, Na+, K+, SiO2−, Fe2+/3+, and finally Al3+
Goldich Dissolution Series
method of predicting the relative stability or weathering rate of common igneous minerals on the Earth’s surface, with minerals that form at higher temperatures and pressures less stable on the surface than minerals that form at lower temperatures and pressures.
Most common and abundant mineral group in the earth’s crust
Plagioclase
The Ca endmember in the plagioclase series
Anorthite
The Na endmember in the plagioclase series
Albite
The order of plagioclase minerals from Ca to Na endmembers
Anorthite, Bytownite, Labradorite, Andesine, Oligoclase, Albite
Mohs hardness of all plagioclase
6 to 6.5
Liquidus of plagioclase
1,215 °C (2,219 °F)
Perthite
Used to describe the intergrowth of two feldspars that are formed through exsolution (homogenous mixture of two different kinds of atoms)
Miscibility Gap
Where a mixture exists as two or more phases (coexistence), the constituents are not completely miscible.
Area of Influence
The area within which the potentiometric surface is lowered by withdrawal or raised by injection, of water through a well
Aquifer
A geologic unit that is saturated and sufficiently permeable to transmit significant economic quantities of water to wells and springs.
Capillary Fringe
The lowest part of the vadose zone, immediately above the water table, where water is under pressure that is less than atmospheric pressure.
Confined Aquifer
An aquifer overlain by a confining layer of low permeability.
Connate Water
Water trapped in the pores of a sedimentary rock at the time of deposition; fossil water.
Darcy
A unit of intrinsic permeability = 9.87 x 10^-9 cm^2.
Darcy’s Law
The basic equation describing groundwater flow put forth by darcy: Q=KiA (K = hydraulic conductivity i=hydraulic gradient A is cross-sectional area of aquifer through which flow occurs (w x b, ft^2))
Discharge Area
An area where subsurface water is discharged to land, bodies of water or the atmosphere.
Effective Porosity
The percentage of the total volume of a soil or rock that consists of interconnected pore space. The term is sometimes used analogously to specific yield.
Field Capacity
The quantity of water held by the soil or rock against the pull of gravity Field capacity is dependent on the length of time the soil or rock has been undergoing gravity drainage, while specific retention is not.
Flow Net
Two-dimensional representation of flow lines and equipotentials.
Ghyben-Herzberg Principle
The principle that states that the depth to which fresh water extends below sea level is approximately 40 times the height of the water table above sea level.
Head
A measure of the potential energy of a fluid at any given point with respect to a given datum. In practice, it is the elevation to which water rises at a given point as a result of reservoir pressure.
Hydraulic Conductivity (K)
The capacity of a porous medium to transmit water. The rate at which fluid can move through a permeable medium depends on properties of the fluid (Viscosity and specific weight) and properties of the medium (intrinsic permeability).
(K)
Hydraulic conductivity
Hydraulic Gradient (I)
Rate of change in total head per unit of distance of flow in a given direction.
(I)
Hydraulic Gradient
Intrinsic Permeability (Ki)
A property of the porous medium that measures the relative case with which a fluid can be transmitted through it under a hydraulic gradient. It is dependent upon the pore size and is measured in darcys.
(Ki)
Intrinsic Permeability
Juvenile Water
Water that is derived directly from magma and is thought to have come to the Earth’s surface for the first time.
Meinzer
A unit of hydraulic conductivity in gpd/ft^2. Rate of flow in gallons per day through a cross section of 1 square foot under a unit hydraulic gradient at 60 degrees F.
Perched Groundwater
Unconfined groundwater separated from an underlying body of groundwater by an unsaturated zone.
Permeability
The property of a porous rock or soil for transmitting a fluid. It measure the relative ease of flow under unequal pressure.
Porosity (n)
The percentage of the bulk volume of a rock or soil that is occupied by void space.
(n)
Porosity
Potentiometric Surface
A surface that represents the total head of groundwater and is defined by the level to which water will rise in a well.
Recharge Area
An area where water infiltrates downward into the saturated zone.
Runoff (R)
That part of precipitation appearing in surface streams.
Specific Retention (Sr)
Ratio of the volume of water a soil or rock can retain against gravity drainage to the total volume of the soil or rock, usually stated as a percentage.
Specific Storage (Ss)
Amount of water per unit volume of a saturated formation that is stored or expelled from storage due to compressibility of mineral skeleton and pore water per unit change in head. Units are ft^-1.
Storativity or Storage Coefficient (S)
Volume of water that a permeable unit releases from or takes into storage per unit surface area of the aquifer per unit change in head. In an unconfined aquifer, storage = specific yield.
Specific Yield (Sy)
Ratio of the volume of water that drains from a saturated soil or rock due to gravity to the total volume of soil or rock, stated as a percentage.
Transmissivity (T)
The capacity of an aquifer to transmit water of the prevailing kinematic viscosity. T=Kb, where b = saturated thickness of the aquifer Dimensions are gpd/ft or ft^2/day.
Unconfined Aquifer
An aquifer having a water table.
Underflow (U)
Groundwater that flows beneath the bed or alluvial plain of a surface stream, especially in arid regions.
Vadose Zone or Zone of Aeration
A subsurface zone containing water under pressure that is less than atmospheric pressure. It is measured from the ground surface to the water table.
Water Table
The surface within unconfined groundwater at which the hydraulic pressure is equal to atmospheric pressure.
Watershed
The region drained by a stream or body of water, or a drainage divide.
Sustainable Yield
Can be defined by equating recharge rates to pumping rates in a way that pumping rates do not exceed recharge rates.
Macro Pore Flow
Occurs along worm holes, root holes or fracture
Funneled or Focused Flow
Occurs along lenses that may concentrate and deflect the direction of flow
Unstable Flow
Flow that breaks through interfaces and creates fingers that become more conductive to water flow, as compared to adjacent areas that are dry.
Angular Unconformity
Unconformity between two groups of rocks that are dipping at different angles. The older rocks below are often dipping more steeply than the rocks above.
Disconformity
A type of paraconformity in which the rocks above and below are essentially parallel but the unconformity surface is not parallel to the bedding.
Nonconformity
sedimentary deposits rest upon older igneous or metamorphic rocks
Paraconformity
Unconformity is parallel to the strata above and below it.
Eon
Four subdivisions of time on Earth: Three Eons - hadean, Archean, and Proterozoic - Cover almost half the time on Earth; The fourth eon - Phanerozoic - incorporates the Paleozoic, Mesozoic and Cenozoic eras.
Epoch
Subdivisions of the Tertiary and Quaternary periods.
Era
Subdivisions of the Phanerozoic: Paleozoic, Mesozoic and Cenozoic.
Ga
Abbreviation for Giga-annum; one billion years.
GIS
Geographic Information System, a computer-based tool used for mapping, analyzing and visualizing geographically referenced data.
GPS
Global Positioning System, a radio navigation system that determines the exact location, time and velocity from triangulation.
Ka
Abbreviation for Kilo-annum; one thousand years
Key Beds
A well-defined, easily identified strata that is distinctive enough to be useful in correlation in mapping.
Ma
Abbreviation for Mega annum/ one million years
Magnetic Declination
The angle between true North and magnetic North.
Period
Subdivisions of the three eras: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian in the Paleozoic, Triassic, Jurassic, and Cretaceous in the Mesozoic, and Tertiary and Quaternary in the Cenozoic.
Rule of V’s
Outcrop pattern of a formation or fault as it crosses a valley.
State Plane Coordinate System
A two dimensional coordinate system developed by the National Geodetic Survey for use in states and counties. There are 130 zones in the U.S. defined by county, state, and international boundaries. Convenient for local use, however cannot be used in large regions and coordinates need to be converted to latitude and longitude.
Township and Range
A surveyed unit of the Public Land Survey System that forms a 6 mile by 6 mile square and is divided into 36 sections (identified by number) that each have 16 individual 40 acre parcels (identified by letter). Townships are measured in rows north and south of a Baseline and Ranges are measured in columns east and west of a Principal Meridian.
Periods of the Paleozoic Era
Cambrian
Ordovician
Silurian
Devonian
Carboniferous
Permian
Periods of the Mesozoic Era
Cretaceous
Jurassic
Triassic
Epochs of the Cenozoic
Paleocene
Eocene
Oligocene
Miocene
Pliocene
Pleistocene
Holocene
Periods of the Cenooic
Tertiary
Quaternary
Start of the Mesozoic Era
65.5 Ma
Start of the Paleozoic Era
251 Ma
Beginning of the Paleozoic Era
542 Ma
Period known as Age of Man
Quaternary
Period known as Age of Mammals
Tertiary
Period known as Age of Reptiles
Cretaceous - Triassic (Mesozoic)
Period known as Age of Amphibians
Permian - Carboniferous (Pennsylvanian and Mississippian)
Period known as Age of Fish
Devonian - Silurian
Period known as Age of Invertebrates
Ordovician - Cambrian
Subperiods of the Tertiary
Neogene and Paleogene
Subperiods of the Carboniferous
Pennsylvanian and Mississippian
Law of Initial Horizontality
Assumes the sequence of layers was deposited horizontally. The oldest layer is on the bottom and the youngest layer is on the top.
Law of Superposition
States that the oldest layer is on the bottom and the youngest layer is on the top. Assumes that the layers have not been overturned during deformation.
Another Way of stating is that the beds become younger in the direction of dip. Applies to any layered rock sequence such as sedimentary units or extrusive igneous rocks.
Cross-Cutting Relationships
feature that is cut is older than the feature that cuts across it.
Lateral Continuity
Implies there are sedimentary layers that when deposited covered a large area extending laterally in all directions. Rocks would be considered laterally continuous even though they may be separated by uplift or erosion.
Faunal and Floral Evolutionary Age Relations
Evolutionary development of fossils can suggest a sequence of age. Older and more primitive fossils are usually found below younger fossils. Extinctions may break the pattern and new patterns may emerge. Fossils can be used to correlate with stratigraphic sequences in other areas.
Law of Inclusions
inclusions in a rock signify that the inclusions are older than the rocks in which they are included. Inclusions may also provide clues of the provenance at the time of formation.
Metamorphism Age Relations
Metamorphosed beds are younger than the rock as it existed before metamorphism.
Sole Marks
Coarse sand or silt layer is deposited onto mud. Erodes pits and scars into the mud layer and then the depressions are in-filled with the more coarse material.
Physical continuity
strata are generally continuous unless eroded, interrupted by faulting truncated by an unconformity, shaped as a lenticular body, or deposited locally.
Lithology correlation
Distinctive units can be used to correlate with a high degree of confidence.
Sequence of strata correlation
Rock units may repeat in an orderly fashion allowing a correlation of the entire sequence to be made.
Rock Property Correlation
Strata may be correlated by means of their electrical or radioactive properties as measured on a well log.
Index fossil correlation
appearance of a fossil, evolution through time and finally its disappearance yields valuable information which could then be correlated to similar rocks in other areas.
Fossil Assemblage Correlation
Groups of several fossil species are more useful for correlations because there is a greater opportunity for the assemblage to be present than a single species. Assemblages may also permit a more detailed correlation where stratigraphic ranges overlap.
Unconformity
Time break in a sequence of beds
Rule of V: Horizontal Bedding
V upstream parallel to topography
Rule of V: Dip Upstream
V upstream, outside topography
Rule of V: Vertical bedding
Straight lines cutting across valley topography
Rule of V: Dip downstream greater than valley gradient
V downstream
Rule of V: Dip downstream equals valley gradient
Parallel lines along valley sides
Rule of V: Dip downstream less than valley gradient
V upstream inside topography
Downwarp
Synform - can’t be assumed to be a syncline unless the ages of the units are known.
Upwarp
Antiform - can’t be assumed to be a anticline unless the ages of the units are known.
Anticline plunge
In the direction of the closure of the U
Syncline plunge
Opposite direction of the closure of the U
Juxtaposition of noncontiguous sedimentary facies
Sedimentary facies that do not usually occur next to each other may be moved laterally by strike slip faults
Sag Pond
a body of fresh water collected in the lowest parts of a depression formed between two sides of an active strike-slip, transtensional or normal fault zone.
scarplet
a fault only a few inches to a foot high.
Triangular Facets
A triangular face having a broad base and an apex pointing upward; specif. the face on the end of a faceted spur, usually a remnant of a fault plane at the base of a block mountain. A triangular facet may also form by wave erosion of a mountain front or by glacial truncation of a spur.
Slickensides
naturally polished rock surfaces that occur when the rocks along a fault rub against each other, making their surfaces smoothed, lineated, and grooved.
Grooving
A striation created by a geological process, on the surface of a rock or a mineral.
Drag
a minor geological fold produced in soft or thinly laminated beds lying between harder or more massive beds in the limbs of a major fold
Gouge
a filling material such as silt, clay, rock flour, and other kinds of geological debris in joints, cracks, fissures, faults, and other discontinuities in rocks
Breccia
is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix. A breccia may have a variety of different origins, as indicated by the named types including sedimentary breccia, tectonic breccia, igneous breccia, impact breccia, and hydrothermal breccia.
Megabreccia
a breccia composed of very large rock fragments, sometimes kilometers across, which can be formed by landslides, impact events, or caldera collapse.
Mylonite
a metamorphic rock formed by ductile deformation during intense shearing encountered during folding and faulting, a process termed cataclastic or dynamic metamorphism. This process involves nearly complete pulverisation of the parent rock so the original minerals are almost completely broken down and recrystallise as smaller grains which are tightly intergrown, forming a dense, hard rock. As a result of the shearing encountered during formation, recrystallised minerals grow preferentially along planes of foliation parallel to the direction of shear.
Silicification
the replacement of original skeletal material accomplished through the concurrent dissolution of calcium carbonate and precipitation of silica. The processes is aided by the nucleation of silica to organic matter which surrounds the mineral crystallites within the shell. It is far more common in Paleozoic than younger deposits, is more likely to occur in organisms with low magnesium calcite shells, in carbonate sediments, and in environments with elevated dissolved silica.
Fenster
An erosional feature through he overlying thrust sheet into the block underlying the fault, creating a “window”.
Klippe
An outlier of the overlying thrust sheet that has been isolated from the rest of thte thrust by erosion.
Concordant Features
Consistent with bedding planes
Sill
a concordant feature, that is, they are emplaced along zones of weakness and geographically restricted
Dike
parallel-sided, generally of constant thickness, and are relatively restricted in areal extent. Discordant features, cutting across many lithologic units
Discordant Features
Cut across other lithologic units
Xenolith
Rock fragment that becomes enveloped in a larger rock during the latter’s development and solidification. Almost exclusively used to describe inclusions in igneous rock entrained during magma ascent, emplacement and eruption.
Large igneous intrusions
forcefully emplaced, forma circular shape, have foliation parallel to the margins, and lack xenoliths of country rock. Country rock dips away from the intrusive contact. Folds and faults are usually present.
Hornfells
a dark, fine-grained metamorphic rock consisting largely of quartz, mica and particular feldspars. It was subjected to the heat of contact metamorphism at a shallow depth. Since pressure does not play a significant role, it is often made up of mineral grains that are equidimensional in shape and without a preferred orientation.
Contact Metamorphism
Rocks are formed with concentric bands around the boundaries of intrusive igneous rocks. The bands or rings are superimposed on other stratigraphic and structural boundaries.
Regional metamorphism
laterally extensive, covering the entire map. Rocks are slate, phyllite, schist, gneiss, migmatite and eclogite.
Cataclastic metamorphism
identified by faults that have a zone of breccia, cataclasite, or mylonite associated with them.
Slate
is a fine-grained, foliated metamorphic rock that is created by the alteration of shale or mudstone by low-grade regional metamorphism. Slate is composed mainly of clay minerals or micas, depending upon the degree of metamorphism to which it has been subjected. The original clay minerals in shale alter to micas with increasing levels of heat and pressure. Slate can also contain abundant quartz and small amounts of feldspar, calcite, pyrite, hematite, and other minerals.
Tectonic environment that forms slate
usually a former sedimentary basin that becomes involved in a convergent plate boundary. Shales and mudstones in that basin are compressed by horizontal forces with minor heating. These forces and heat modify the clay minerals in the shale and mudstone. Foliation develops at right angles to the compressive forces of the convergent plate boundary to yield a vertical foliation that usually crosses the bedding planes that existed in the shale.
Phyllite
These are almost always convergent plate boundary environments involving continental lithosphere. Phyllite forms in areas of regional metamorphism where where beds of sedimentary rocks have been subjected to moderate heat and compression by the colliding of continental plates and mountain-building events. Both slate and phyllite form in sedimentary basins that are deeply buried, or in accretionary wedges above subduction zones. a foliated metamorphic rock that is made up mainly of very fine-grained mica. The surface of phyllite is typically lustrous and sometimes wrinkled. It is intermediate in grade between slate and schist
schist
is a foliated metamorphic rock made up of plate-shaped mineral grains that are large enough to see with an unaided eye. It usually forms on a continental side of a convergent plate boundary where sedimentary rocks, such as shales and mudstones, have been subjected to compressive forces, heat, and chemical activity. This metamorphic environment is intense enough to convert the clay minerals of the sedimentary rocks into platy metamorphic minerals such as muscovite, biotite, and chlorite. To become schist, a shale must be metamorphosed in steps through slate and then through phyllite. If the schist is metamorphosed further, it might become a granular rock known as gneiss. a metamorphic rock with well-developed foliation. It often contains significant amounts of mica which allow the rock to split into thin pieces. It is a rock of intermediate metamorphic grade between phyllite and gneiss.
gneiss
Gneiss usually forms by regional metamorphism at convergent plate boundaries. It is a high-grade metamorphic rock in which mineral grains recrystallized under intense heat and pressure. Gneiss can form in several different ways. The most common path begins with shale, which is a sedimentary rock. Regional metamorphism can transform shale into slate, then phyllite, then schist, and finally into gneiss.
During this transformation, clay particles in shale transform into micas and increase in size. Finally, the platy micas begin to recrystallize into granular minerals. The appearance of granular minerals is what marks the transition into gneiss.
migmatite
place holder
7.5 minute quad scale
1:24,000
15 minute quad scale
1:62,500
30 x 60 minute scale
1:100,000
1 degree x 2 degree scale
1:250,000
metamorphic rocks
have been modified by heat, pressure and chemical processes, usually buried deep below Earth’s surface. These extreme conditions have altered the mineralogy, texture and chemical composition of the rocks.
Foliated metamorphic rocks
have a layered or banded appearance that is produced by exposure to heat and directed pressure. Examples slate, phyllite, schist, gneiss.
Examples of Non-foliated metamorphic rocks
Hornfels, Marble, Novaculite, Quartzite and Skarns.
Anthracite
Highest rank of coal. It has been exposed to enough heat and pressure that most of the oxygen and hydrogen have been driven off, leaving a high-carbon material behind. It is bright, lustrous and breaks with a semi-conchoidal fracture. Often referred to as “hard coal”.
Gneiss
A foliated metamorphic rock that has banded appearance and is made up of granular mineral grains. Typically contains abundant quartz or feldspar minerals.
Hornfels
a fine-grained non-foliated metamorphic rock with no specific composition. It is produced by contact metamorphism. Hornfels is a rock that was “baked” while near a heat source such as a magma chamber, sill or dike.
Lapis Lazuli
Famous blue gem material, formed through contact metamorphism or hydrothermal metamorphism, where limestone or marble has been altered.
Marble
Non-foliated metamorphic rock that is produced from the metamorphism of limestone or dolostone. Primarily composed of calcium carbonate.
Mariposite
Metamorphic rocks that contain enough green mica to impart a green color, although major constituents are quartz, calcite, dolomite, ankerite or barite. These rocks have been altered by hydrothermal activity, and usually thought to have a serpentinite protolith. Mariposite was sometimes a host rock of gold.
Novaculite
a dense, hard, fine-grained, siliceous rock that breaks with a conchoidal fracture. It forms from sediments deposited in marine environments where organisms such as diatoms (single-celled algae that secrete a hard shell composed of silicon dioxide) are abundant in the water.
Quartzite
a non-foliated metamorphic rock that is produced by the metamorphism of sandstone. It is composed primarily of quartz.
skarn
a rock characterized by its formation rather than its mineral composition. It often forms when carbonate rocks near a magma body are altered by contact metamorphism and metasomatism. Various minerals, gems, and even precious metals can sometimes be found in skarn.
Soapstone
a metamorphic rock that consists primarily of talc with varying amounts of other minerals such as micas, chlorite, amphiboles, pyroxenes, and carbonates. It is a soft, dense, heat-resistant rock that has a high specific heat capacity. These properties make it useful for a wide variety of architectural, practical, and artistic uses.
one degree of latitude scale in feet (miles)
364,000 ft (69 miles)
one minute of latitude scale in feet (miles)
6068 ft (1.15 miles)
one second of latitude scale in feet
101 Ft
Large-scale maps are useful for…
1:24,00 (1” = 2000’)
1:1,200 (1” = 100’)
1:600 (1” = 50’)
Engineering planning and geologic mapping in developed areas or areas where more detail is needed. A 1:1,200 or 1:600 scale map is usually private surveys, fault investigations, locating utilities or roads, housing developments or other jobs specific to small areas.
Intermediate-scale maps are useful for…
1:50,000
1:62,500
1:100,000
County-wide or regional planning and land management.
Small-scale maps are useful for
1:250,000
1:500,000
1:1,000,000
Often state wide data, typically include the major features such as state and national parks, cultural boundaries, airports, major roads and railroad lines.
Clarke’s ellipsoid
the first ellipsoid of the earth and first established in 1866. The horizontal data based on this ellipsoid was NAD27.
NAD83
Horizontal datum that is based on the geodetic reference system (GRS80).
Chlorite
Common sheet silicate minerals that form during the early stages of metamorphism. Most often found in rock environments where minerals are altered by heat, pressure, and chemical activity, with low temperatures a few miles of earth’s surface. Also found as retrograde minerals in igneous and metamorphic rocks that have been weathered. Rocks that commonly contain abundant chlorite include greenschist, phyllite, chlorite schist and greenstone.
Physical properties of chlorite
Green in color, have foliated appearance, perfect cleaveage, and an oily or soapy feel. Variable chemical composition gives them a range of hardness and specific gravity.
Physical properties of chlorite
Green in color, have foliated appearance, perfect cleavage, and an oily or soapy feel. Variable chemical composition gives them a range of hardness and specific gravity.
Cataclasite
a cohesive granular fault rock that has been formed through brittle deformation mechanisms containing pieces of the fractured pre-existing rock type.
Karst
a term that is applied to the topography of a region which is underlain by limestone, dolomite, gypsum, or other rocks which can be affected by dissolution.
Karst Topography
is characterized by surface depressions in which water is intercepted and diverted into underground caverns and passageways.
Four conditions necessary for karst development
1) a soluble rock, preferably limestone, at or near the surface
2) a dense rock, highly jointed and thin-bedded
3) Entrenched valleys below uplands underlain by soluble and well-jointed rocks
4) a region of moderate to abundant rainfall
Four most important U.S. regions for karst
Florida, southern Missouri, southerly trending belt from south-central Indiana into central Tennessee, and in the Appalachians from Alabama to Pennsylvania.
dripstone
travertine deposits that result from the calcium carbonate-rich water dripping from the ceiling of a cave or cavern.
Stalactites
downward protrusion of dripstone deposit.
stalagmites
upward protrusion of dripstone deposit.
sinkholes
most commonly observed feature of karst terrain. Sinkholes are circular depressions that are commonly funnel-shaped and can be a few feet to a hundred feet in diameter.
Compound Sinkhole
when sinkholes enlarge and combine with adjoining sinkholes.
solution sinkholes
occur when rainwater comes into contact with carbonate bedrock either directly or through a thin covering of soil. Water moves through joints, fractures and bedding planes and dissolves the carbonate, forming small depressions at the surface. The depressions subsequently may focus the accumulation of surface water or debris that settles in the depressions. The resultant landform is gently undulating with shallow depressions and mounds.
Cover-subsidence sinkholes
Form where sand overlies the carbonate bedrock. As water moves thorough the sand and into the joints and fractures of the bedrock, it carries some of the sand with it. Additional sand fills the vacated space, eventually forming a depression at the surface.
Cover-collapse sinkholes
Develop where there is a thick layer of clay above the soluble bedrock. The water moves through the clay and starts dissolving the bedrock below. As the cavity grows in the bedrock the cohesive clays above bridge the opening and eventually the cavity roof collapses and breaches the ground surface in catastrophic fashion. Often these sinkholes are steep-sided chimney-like structures, but until they fail abruptly there is little evidence of their existence at the surface.
Helictite
An irregular twiglike deposit that forms in a cavern where there is not enough water to form drips but where the surface remains damp allowing the calcium carbonate to grow in any direction.
Travertine
A deposit of calcium carbonate precipitate that can be found in limestone caverns coating the cavern walls, floors and ceilings.
blind valley
A valley that ends at a swallow hole due to a prolonged period of upstream erosion above the sinkhole.
Cavern
Large caves that may extend in any direction, have one or several levels, and are created by solution of limestone along joints and bedding planes.
Hum
Isolated hill remnants due to erosion by solution in karst terrain.
Karst Window
A hole in the ground in which one can observe an underground stream flowing from one cavern to another. A hole in a cavern which breaks to the surface.
Lapies
Grooved or fluted surface resulting from the solution of limestone at or near the surface in an area of high relief. The grooves range in width from a few millimeters to more than a meter in width and commonly result in knifelike ridges.
Natural tunnels & bridges
Features produced by the underground flow of water in karst terrain. When the tunnel sections collapse leaving only small segment, bridges are formed.
Polje
An elongated basin with a flat floor and steep walls formed by solution of a previously faulted or folded structure. This feature can be 30 miles or more in length.
Sink
The point at which a sinking creek ends, often in an observable swallow hole.
Sinkhole or karst plain
A limestone plain exhibiting sieve-like characteristics resulting from numerous sinkholes intercepting any surface water and diverting them to subsurface channels.
Sinkhole pods or karst lakes
A pond or lake resulting from the clogging by clay of a doline sinkhole that perches water above the water table.
Sinking creeks
Any surface creek or stream which disappears underground in karst terrain; many disappear in a swallow hole.
Solution Valley or Karst Valley
A transitional feature between surface and subsurface drainage in an area of clastic rocks. Valley forms because of extensive collapse and karst development. A special type of blind valley.
Solution-subsidence trough
A non-tectonic feature, up to 10 miles in length, resulting from concurrent subsidence and solution along joints or faults.
Swallow hole
A hole in the bottom of a sinkhole which allows surface water runoff or streams to flow into the subsurface.
Terra rossa
A red clayer (CL-CH) soil found mantling the ground surface and extending into joints or fractures resulting from surface or near surface solution, usually found on moderate to gentle slopes.
Uvala
An elongated karst window that has occurred by the collapse of a extensive portion of a subsurface waterway. These features can extend from 1000 feet to a mile or more.
Conditions to classify snow or ice field as a glacier
1) Must be a large accumulation or mass of ice and snow.
2) It must be located on or principally on land.
3) Must be formed by compaction and recrystallization of snow.
4) Must be evidence of past or present movement
5) Glacier remains from year to year.
Glacial movements
Continental - outward in all directions due to the weight of the snow.
Alpine - directional controlled by the topography.
Drift
All rock and associated material that has been carried by and deposited by a glacier, glacial ice, or water running from a glacier. This term is a general term and includes all those depots that can be further described by the terms till, stratified till, and deposits of glacio-fluvial, glacio-lacustrine, glacio-eolian, and glacio-marine origin.
Drumlin
An elongated ellipsoidal feature which can be composed of a wide variety of materials ranging from till to relatively large rock fragments; some even have a bedrock core. These streamlined hills are usually clustered and are found near the terminal or recessional moraines. Many are thought to be deposited after the ice passes around an obstacle.
Esker
These serpentine shaped stratified deposits develop as the load arrived by the streams flowing beneath, within, and above the glacier , once it has become stagnant, is dropped. They have the appearance of inverted stream channels, often with branching, and they may join the outwash plain at the glacier margin.
Kame and Kame Terrace
A small hummock or terrace of ice-contact drift that has resulted from the deposition of sediment either in crevasses at the surface of the glacier, on the irregular surface of stagnant glaciers, or often from streams flowing at the edge of the glacier along the contact of the ice with the valley wall. The materials are typically stratified and contain poorly sorted sands (SW) and gravels (GW).
Kettle
A depression in the postglacial terrain formed by the melting of a large stagnant ice block which allows for the settlement of the overlying glacial drift. In some area the outwash plains pitted with may kettles. This could results fr4om the stagnation of a laterally extensive sheet of ice with varying thickness.
Arcuate Terminal Moraine
An arcuate moraine that has been deposited at the terminus of the glacier, marking the furthest progression of the glaciation. Older terminal moraines that are not the maximum extent of glaciation are typically destroyed by subsequent glacial advances incorporating the older moraine material with the younger.
Ground Moraine
Often used interchangeably with till plain. Can be composed of both the material contained within the glacier as well as that being moved along at its base.
End Moraine or Terminal Moraine
The end moraines found at the maximum extent of a continental glaciation are similar to those found in alpine glaciation though they tend to be much more extensive and often have less steep slopes, occasionally making it difficult to distinguish between the ground moraine and the end moraine materials.
Recessional moraine
Moraines that have formed during a temporary hiatus in the retreat of the ice sheet. There are often many recessional moraines that form as the retreat occurs.
Outwash Plain
A broad plain composed of outwash: stratified debris that is carried by meltwater streams both in front of and beyond the terminal or end moraine. The outwash plain is typically comprised of coarser grained materials (SW, GW) closer to the terminus of the glacier grading to finer materials with increased distance.
Swell and Swale Topography
Till deposits rich in clay may result in a gently undulating surface which often is also found in areas that have had multiple glaciations.
Till
An unsorted, unstratified glacial deposit composed of a heterogeneous mixture of clay (CL), silt (ML) , Sand (SW), gravel (GW), and boulders. It is usually unconsolidated and deposited directly by a glacier without having been reworked by meltwater.
Till plain
Also called ground moraine, deposition by an ice cap of glacial till forming a relatively flat to undulating surface which covers an extensive area and buries the preglacial topography.
Ice-scoured plain
An assemblage of erosional landforms on exposed bedrock resulting from the flow of an ice cap. It exhibits may of the same surficial features that are found in areas of alpine glaciation such as striations, grooves and polished surfaces, as well as the development of roche mountonnees or mammillated surfaces.
Roche moutonnee
An elongated bedrock knob which is oriented parallel to the direction of glacial flow and has a smooth rounded upstream end and usually a steep rough downstream end where the glacier plucked out the rock as it moved away.
Streamlined topography (mammillated surface)
A series of smooth rounded erosional rock mounds alternating with parallel valleys resulting from the smoothing off of a mountainous region by the ice cap.
Knob and basin topography
Also called knob-and-kettle topography, hummocky landscape consisting of knolls or mounds of glacial drift in an area also interspersed with basins or kettles. The basins often contain water. (Alpine Glaciation)
Lacustrine plains
A plain that has formed by the filling of a lake with lake sediments and alluvium which has been deposited along the margin of the glacier. Characterized by very flat valley bottoms in hilly terrain. (Alpine Glaciation)
Moraines
A mound or ridge composed of accumulated glacial drift or till deposited directly by the glacier. Moraines are composed of a heterogeneous collection of unsorted and unstratified clay (CL), silt (ML), sand (SW), gravel (GW) and boulders. Many of the larger clasts are faceted and have striations or polish due to the abrasion during the movement of the glacier. (Alpine Glaciation)
Lateral Moraine
A linear moraine located along the edge of a valley glacier and composed of materials deposited on the glacier from the valley walls. (Alpine Glaciation)
Medial Moraine
A linear moraine paralleling the valley walls which occurs when two valley glaciers merge joining the two inside lateral moraines from the two or more tributaries as they flow into the more major drainage. (Alpine Glaciation)
Valley Train
A long, narrow deposit of outwash (sand and gravel), deposited by glacial meltwater, which begins at the end moraine and extends down valley (Alpine Glaciation)
Arete
A jagged sharp sawtooth-like ridge that results form the growth of cirques on opposite sides of a mountain ridge by alpine glaciation.
Cirque
A horseshoe-shaped hollow high on a mountainside that was created by the erosive action at the head of a glacier. (Alpine Glaciation)
Col
A narrow sharp-edged pass or sag between cirque head and side walls along an arete. (Alpine Glaciation)
Fjords, Fiards (Fjards)
A submerged glacial trough or valley at its seaward end resulting from the raising of sea level as the glaciers melted. The fiard is a shallower and shorter, but often broader, feature than the fjord. (Alpine Glaciation)
Glacial polish
A smooth surface produced on bedrock by abrasion by the movement of a glacier. (Alpine Glaciation)
Glacial steps or stairway
A series of cross-valley steps extending down from the cirque, these steps are characterized by a relatively flat floor or with a slight up valley slope broken by steeper sections stepping down valley. (Alpine Glaciation)
Glacial trough (U-shaped valley)
A steep-sided valley that extends down from the cirque in which glacial action has widened and deepened an existing valley. (Alpine Glaciation)
Hanging valley
A U-shaped glacial tributary valley truncated by a deeper U-shaped glacial main valley leaving a valley whose mouth is relatively high on the main valley wall. The discordance is due to the greater erosive power of the main glacier. (Alpine Glaciation)
Horn
A jagged sharp peak at the high point in an arete which has been sculpted by the erosional action of three or more cirques. This pyramidal feature is the remainder of the original mountain summit in a region modified by alpine glaciation.
Monuments (tinds)
A horn that has been isolated by the lateral interstation of cirques. (Alpine Glaciation)
Paternoster lakes
A series or chain of lakes occupying the glacial steps. (Alpine Glaciation)
Striations
Lines scrapped into the bedrock by rocks being carried along at the base of the glacier. Striations generally indicate the direction of glacier movement. Larger rocks create grooves or grooved rock that can be as big as a valley. (Alpine Glaciation)
Tarn
A small deep lake formed in a cirque basing. (Alpine Glaciation)
Trough lakes
Similar to fjords in that they consist of a long glacial trough and contain water but are found above sea level. (Alpine Glaciation)
Truncated or faceted spur
A ridge in a pre-glacial valley that has been truncated by the abrasion of glacial action as it straightened the valley. Varying degrees and shapes of truncation are possible, and in some cases may mimic faceted spurs caused by faulting and uplfit. (Alpine Glaciation)
Base Level
The lowest level beyond which a stream cannot erode its bed.
Bed Load
heavier particles (boulders, pebbles, gravel and sand) that travel along the bottom of a channel by bouncing (saltation) or traction. They are not carried continuously in the water column.
Runoff
The portion of precipitation appearing in streams.
Sheet Flow
Unconcentrated laminar overland flow that contributes ot the development of the valleys, valley systems and slopes.
Sheetwash
the material transported by sheetflow
Suspended sediment
primarily fine inorganic particles of clay and silt (typically < 0.063 mm. It also may include fine sand (0.63-0.250 mm) and particulate organic matter suspended in the water column.
GW
Well-graded gravels, gravel-sand mixtures, little or no fines (Clean Gravels - Less than 5% fines)
GP
Poorly-graded gravels, gravel-sand mixtures, little or no fines (Clean Gravels - Less than 5% fines)
GM
Silty gravels, gravel-sand-silt mixtures (Gravels with fines - More than 12% fines)
GC
Clayey gravels, gravel-sand-clay mixtures (Gravels with fines - More than 12% fines)
SW
Well-graded sands, gravelly sands, little or no fines. (Clean Sands - Less than 5% fines)
SP
Poorly graded sands, gravelly sands, little or no fines (Clean Sands - Less than 5% fines)
SM
Silty sands, sand-silt mixtures (Sands with fines - More than 12% fines)
SC
Clayey sands, sand-clay mixtures (Sands with fines - More than 12% fines)
ML
Inorganic silts and very fine sands, rock flour, silty or clayey fine sands or clayey silts with slight plasticity
CL
Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays
OL
Organic silts and organic silty clays of low plasticity
MH
Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts
CH
Inorganic clays of high plasticity, fat clays
OH
Organic clays of medium to high plasticity, organic silts
PT
Peat and other highly organic soils
Silts and clays - Liquid limit less than 50%
L Classificaltion
Silts and clays - Liquid limit 50% or greater
H Classification
Alluvial Fans
Alluvial fans develop when the stream gradient becomes too flat as it exits the hilsl and the water becomes too slow to carry the sediment load. The sediment load is deposited at the exit from the hills where the stream intersects the lowland valley bottom. Alluvial fans are created where torrential rainfall occurs in arid environments. In general, fans consist of a wide range of sand (SW) and gravel (GW) grain sizes. The larger sies are found at the entrance to the valley and finer grains are found farther away from the hills.
Bajadas
Coalescing alluvial fans
Deltas
When streams enter lakes or seas the flow branches out and sedimentation takes place because of the change in gradient. The coarser grains settle quickly into forest beds sloping offshore. .The turbulence at the point of entry allows the suspended load to be carried further offshore and to be deposited horizontally as bottomset beds. As the forest beds progress offshore the fine grained materials in suspension can drop out as nearly horizontal topset beds overlying them. The topset and bottomset beds consist of deposits of finer grained silts (ML) and clays (CL).
Gravel Bars (Sand Bars)
Gravel bars (GP) and sand bars (SP) can develop midstream when the flow velocity of the water declines where it borders with a higher velocity flow in the stream. These bars are usually linear in the flow direction. Often these are relatively well sorted or poorly graded deposits.
Point Bars
When sediment is deposited at the bend in a stream, inside of the turn and are called a Point Bar.
Natural Levees
Form when flood stage has been reached and as the river recedes. The water velocity declines dropping some of the sediment load parallel to the shore. The river moves more toward mid channel as the water drops making the levee higher towards the main channel and lower towards the shore. These levees are generally formed of sand and coarse silts (SW-ML)
Braided Streams
In channel deposition of sands (SW) and gravels (GW) in a braided pattern is due to changes in the velocity of the water within the channel. Increased erosion overloads the stream’s capacity to carry the bed load. When the water is blocked up by deposition it moves to a place where the water is traveling faster, thus moving the bed load around. The materials are eroded or deposited intermittently depending on water velocity. Erosional braiding can occur in bedrock channel bottoms when the resistance to erosion of the bedrock is not uniform.
well sorted =
poorly graded
well graded =
poorly sorted
Free Meanders
Free meanders form in valley bottoms on flat flood plains and can change course by eroding river banks and depositing material.
Incised Meanders
Form on initially flat surfaces but if flow increases or the underlying materials are soft, the stream erodes downward creating a deeper meander that no longer allows the water to move out of the channel.
Ripple Marks
There are two types of ripple marks. Asymmetrical ripple marks indicate directional current. The symmetrical ripple marks are indicative of oscillating water.
Peneplains
Broad, relatively flat to gently undulating surfaces that are created as a result of a variety of erosional processes acting over a long period of time, including marine abrasion or sheetwash.
Pediments
slightly inclined planar surfaces. They meet the mountains generally at an abrupt angle on the upper part of the slope and grade into the valley bottom. They are frequently rock floored or have a thin veneer of alluvium. They are often found in arid regions and are prominent in the Basin and Range Province.
Inselbergs
A prominent isolated remnant of a mountain surrounded by a pediment surface.
Stream channel development occurs through what three processes:
Deepening (vertical), Widening(lateral) and lengthening.
Stream channel deepening occurs…
Dominately due to hydraulic action and scouring of the bottom of the valley through the action of the bed load. In mature streams.
Stream channel widening occurs…
Through currents undercutting the channel walls which eventually causes the banks to collapse. It is also caused by runoff and gullying as well as by incoming tributaries.
Stream channel lengthening occurs…
Lengthening can occur as erosion migrates upstream, downstream if there has been uplift or sea level changes, or by expanded meander loops in flat terrain.
Colluvial Stream Profile
Sediments are from hillslope, and debris flows. There is little transport - little deposition
Cascades Stream Profile
Sediments are from stream flow, debris flows and hillslope. There is high transport - low deposition.
Step-pool
Sediments are from stream flow, debris flows and hillslope. More transport of fines and gravels during normal to moderately high flows with little deposition except in low flow conditions
Plane-bed
Sediments are from stream flow bank failure, debris flows. Channels that have a surface that is armored has higher transport than deposition but those unarmored stream bottoms tend to transport.
Pool-riffle
Sediments are from stream flow, bank failure. Deposition limited in that grains eroded from one reach generally are deposited in the next and generally the stream is more transport limited than plane-bed profiles.
Dune-ripple
Sediments are from stream flow, bank failure. Generally fine grained with relatively flat gradients so transport is steady.
Order of Channel Morphology
Bedrock (Steep), Colluvial (>0,1), Cascades (>0.065), Step-pool (0.3 to 0.065), Plane-bed (0.015 to 0.03), Pool-riffle (<0.015), Dune-ripple (<0.015)
Channel Morphology that is debris flow dominated
Bedrock, Colluvial, Cascades
Channel Morphology that is fluvial dominated
Cascades, Step-ppol, Plane-bed, Pool-riffle, Dune-ripple
Channel Morphology where scour occurs
Bedrock, Colluvial, Cascade, Step-pool
Riffles
erosional habitats with fewer deposited fine particles between substrates.
Step pools
Series of pools separated by near-vertical steps that repeat at a frequency of one to four channel widths.
Meander Stream Pattern
form in areas with relatively flat bedding and terrain. Often found within a floodplain. Once a meander is established and if uplift occurs then the meander can become incised.
Oxbow lakes
When a meander cuts through to create a cutoff meander.
Parallel Stream Pattern
Develops on relatively young, steep slopes with a relatively uniform gradient such as found in newly uplifted terrain. This type of terrain is found along the west coast which is tectonically active and exhibits an emerging coastline.
Dendritic Stream Pattern
Common pattern that develops where there is uniform resistance to erosion and no control by structural or lithologic elements. Tributaries branch irregularly with most if not all stream confluences occurring at angles less than 90 degrees. The pattern often indicates relatively horizontal bedding to shallow dip and is found where the slope is gentle to moderate.
Radial Stream Pattern
Radial patterns are similar to parallel patterns in that they both develop on steep slopes that are relatively uniform. The radial pattern is simply a series of roughly parallel stream channels that have developed on a conical shaped hillside such as a volcanic cone or dome causing them to form the radiating appearance.
Deranged Stream Pattern
Have no predictable pattern resulting from irregular surfaces such as are found in glacial or karst terrain where there is no prominent drainage direction. Streams that flow in and out of small bodies of water that occupy low areas and swampy or boggy areas are characteristic.
Braided Stream Pattern
Found in streams that have alternating flooding and dry periods, When it is flooding there is a lot of sediment being carried as suspended and bed loads. As the flooding declines the volume of sediment being carried declines because the energy of the flow has decreased. This deposited sediment creates an irregular stream bottom and the water has to find its way around the deposited material giving it a braided pattern.
Trellis Stream Pattern
Develop where there is strong lithologic controls and are found where there is bedding structure. This is prevalent in the Appalachians where the folded beds create dipping resistant rock formations that make hogbacks with softer formations making the valleys. The nearly right angle tributaries result from cutting across the resistant layers.
Rectangular
Right angle jointing or faulting creates the rectangular pattern. These joints and faults develop in a weakened rock which allows the streams to accentuate the erosion more rapidly as the unjointed rocks are more resistant. This type of drainage is prominent in the Adirondack Mountains.
Annular
Annular drainage patterns form on an eroded upwarped dome or down dropped basin. The ring like pattern develops from erosion of the softer rocks causing the stream to follow the rocks that are softer and more easily eroded. Similar to trellis, only in an enclosed pattern.
Reynolds Number
Calculated to determine whether the flow is laminar or turbulent. Incorporates hydraulic radius (Cross sectional area of the stream divided by the length of the boundary from side to side where water is in contact with the channel), flow velocity, and the ratio between the fluid density and viscosity. Reynold numbers less than 500 represent laminar flow, between 500 to 2000 both laminar and turbulent flow, and greater than 2000 turbulent flow.
Laminar Flow (streamline flow)
fluid travels smoothly or in regular paths. The velocity, pressure and other flow properties at each point in the fluid remain constant.
Turbulent Flow
fluid undergoes irregular fluctuations and mixing.
Advanced or Emerging Coastlines
The west coast, as it is continuing to experience uplift as a result of it being in a tectonically active region of the U.S. This results in a higher energy environment with steep cliffs and many erosional features. The extent to which these features develop is related to the relative resistance of the rocks to erosion.
Characteristics that influence the rate of marine erosion include
Rock Type and strength, joint and fracture patterns, shape of the coastline, tide swing, and the extent and depth of the continental shelf.
Retreated or submerging coasts
The east and Gulf coasts are , in general, submerging coastlines, with a lower energy environment, resulting in mostly depositional features.
Spit
Develop from a wave train that is oblique to the shore causing the sand to be deposited longitudinally projecting from the protruding point on the shore. Attached to the shore at one end. A hook results when the waves swing around, particularly in high seas.
Estuary
partly enclosed coastal body of water in which river water is mixed with seawater. In a general sense, the estuarine environment is defined by salinity boundaries rather than by geographic boundaries.
Tombolo
One or more sandbars or spits that connect an island to the mainland.
lagoon
An area of relatively shallow, quiet water situated in a coastal environment and having access to the sea but separated from the open marine conditions by a barrier. The barrier may be either a sandy or shingly wave-built feature such as a sandbar or a barrier island or coral reef.
Wave Cut Bench / Platform
have been eroded into gently sloping surfaces at the surf level by the waves and the abrasion of the rock debris
Marine Terrace
A wave-cut platform that has been exposed onto land by uplift or a lowered sea level.
Sea Cliff
Sea cliffs are scarp-like features found at the seaward side of marine terraces and are caused by erosion from wave action, frequently from undercutting.
Headlands
The cliffs and upland areas remain in areas where more resistant rocks remain following the erosive action of the waves.
Sea Arches, Caves
Arches and caves develop along headlands or sea cliffs where the waves attack from more than one direction. Caves that continue to be eroded can become arches.
Stacks, Chimneys, or Skerries
These are created when resistant portions of the headlands become separated from the shore by wave action erosion but are located on the wave cut platform. Stacks and chimneys are exposed at high tide whereas skerries are only exposed when the side recedes.
Beaches
composed of well-sorted (poorly-graded) materials that are constantly being broken down by the wave action. Young beaches are often made up of coarser grained materials (gravel). The variation of the intensity of the waver action can cause the beach deposits to move onshore or offshore
Bars
Submerged sand ridges develop when the waves, which are short and steep, break closer to the shore, drawing the sand offshore where it deposits to create a sand bar. This wave type occurs most often in the winter and during storms. Sand bars may then disappear in the summer when the waves are quieter.
Barrier Beaches, Islands
When sand bars become big enough they can become a barrier beach that runs parallel to the shore. If the sand is above the water at high tide long enough, sand dunes develop through wind-borrne transportation, and eventually plants can begin to take hold. If this continues long enough and gets well enough established then a barrier island is formed. Barrier beaches (islands) often form shallow quiet water areas called lagoons on the shoreward side of the beach.
Barrier Island Chains
Several barrier islands running parallel to the shore end to end.
Fault Scarp
caused by the fault movement itself
Fault-line scarp
caused by differential erosion or weathering along the fault causing the scarp to recede from the location of the fault.
Graben
are down dropped blocks that present as valleys.
Horst
Horst are relatively higher blocks that can erode to make triangular facets
Reverse faults form in what type of environment
result from a compressional structural environment in an area that has brittle rocks.
Thrust faults
Reverse fault that has a dip of less than 45 degrees and often are on the order of 20 degrees or less.
Blind Thurst
When a fault does not reach the ground surface.
Nappe
formed by tectonic plate collisions where material has been thrusted on top of the underlying material as much as a mile or two.
Landslide geomorphology is highly dependent on what three variables
Slope
Underlying Geology
The presence of water
Head scarp
The break in slope that marks the uppermost portion of the slide mass where it has broken away from the in-place hillside. Frequently cracks form above the scarp that can be an incipient scarp.
Crown
The undisturbed in-place material above the head scarp of a slide.
Hummocky terrain
A bumpy, irregular ground surface that contains numerous high spots and low spots, which are small closed basins where water can be retained, due to the downslope movement of the landmass.
Transverse cracks
Cracks that form transverse to the slide movement where the slide mass moves over a high spot or ridge under the slide material.
Radial Cracks
Cracks that form parallel to the slide movement at the toe of the slide mass as the material spreads where it is not contained.
Transverse Ridges
Ridges that form transverse to the direction of the slide movement from the compression or thrusting of the upper slide material on the lower part of the slide.
Toe
The lowest part of the slide mass that usually has an arcuate shape where the slide material has moved over original ground.
Foot
The downslope extension of the slide mass beyond the rupture plane in the subsurface.
Rupture surface (slide plane)
The demarcation between the in-place ground and the slide mass.
Speed of Fall Landslide Movement
Rapid
Speed of Topples Landslide Movement
Rapid
Speed of Flow/Avalanche Landslide Movement
Rapid
Speed of Slide (Rotational/Translational) Landslide Movement
Slow
Speed of Lateral Spreads Landslide Movement
Slow
Speed of Creep Landslide Movement
Very Slow
Falls - Common Trigger
Freeze thaw in rocks
Topples - Common Trigger
Freeze thaw in rocks
Flows/Avalanches - Common Trigger
Supersaturated soils
Slides (Rotational) - Common Trigger
Rising Groundwater
Slides (Translational) - Common Trigger
Rising groundwater or shaking
Lateral Spreads - Common Trigger
Rapid under earthquake conditions
Creep - movement observation
So slow that tree trunks will bend upward making a J-Shape
Most prominent and well known form of eolian features
Sand Dunes
Barchan Dune
Crescent-shaped, tails to leeward, rarely vegetated
Leeward
Direction Wind is blowing
Windward
Direction wind is blowing from
Parabolic Dune
Crescent-shaped, tails to windward, often associated with some vegetated cover
Transverse Dunes
Perpendicular to the wind, exhibits the traditional gentle windward slope and the steep slip face nearing the angle of repose. (Both Barchan and Parabolic dunes are a variety of transverse).
Longitudinal Dune (Seif)
Parallel to the wind, thought to develop in areas in which the prevailing wind causes the dunes to lengthen in the direction of the wind but the dune height increases due to the cross winds during periods of irregular wind flow.
Star Dunes
Have 3 or more arms and form from multi-directional winds. These make the tallest dunes because the sand collets in the center.
Blowout
a depression caused by deflation in an area where either migrating dunes exist or a small break develops in the surficial integrity of a stabilized windblown deposit or in some causes the underlying material is composed of a poorly to non-indurated material. (Erosional Landform)
Desert Pavement
Sometimes called desert armor, is a name applied to the relatively flat residual surface of closely-packed, wind-polished stones. This type of condition is the result of the removal of the fine-grained particles by wind and sheetwash. Often these remaining stones are somewhat cemented in place. (Erosional Landform)
Pedestal rocks
Commonly called balanced rocks, these formations are a result of a combination of wind and water erosion (deflation) in an area where there are resistant rocks capping weaker more easily eroded rocks. (Erosional Feature)
Ventifacts
Stones that have been abraded by the wind on at least one side so they are polished or faceted. They are usually only found in unique environment of no vegetation, strong wind and plentiful sand. (Erosional Feature)
Yardang
A long, jagged, sharp-edged ridge between troughs, oriented with the direction of the prevailing winds, in an arid region which is underlain by relatively weak materials. (Erosional Feature)
Soil Profile is dependent on what two factors
Climate and Environment. Breakdown of the organic materials that are deposited on top of the ground and the chemical breakdown of the underlying bedrock.
O-Horizon
The upper most layer of the soil profile. Organic layer which consists principally of relatively undecomposed plant matter.
Zone of Eluviation
A-Horizon - Downward percolation of water through soil horizons that transports soil content from upper layer sto lower levels
A-Horizon
Surface soil (biomantle or zone of eluviation) - This top layer of the soil horizon contains a mixture of organic and mineral materials. Soluble constituents such as iron, aluminum, clay and organic compounds have been leached out. It tends to be darker in color and most of the biological activity such as worms, fungi, bacteria and nematodes are concentrated here.
Zone of illuviation
B-Horizon - Accumulation of dissolved or suspended soil materials in one area or layer as a result of leaching (percolation) from another.
B-Horizon
Subsoil (Zone of illuviation) - The iron, aluminum, clay and organic compounds accumulate in this zone, there is no organic matter, and it has a distinctly different soil structure. The color of this horizon is brighter and stronger or has higher chroma.
C-Horizon
Substratum - Soil forming processes have had little effect on these soils. They lack properties of the other horizons but may accumulate soluble compounds that have passed through the B-Horizon. In saprolites the original rock structure may still be present.
Saprolite
formed by decomposition of rocks that has remained in its original site.
Regolith
The layer of unconsolidated rocky material covering bedrock. Includes all of the weathered material within the profile.
Solum
The altered layer of soil above the parent material that includes the A and B horizons.
Weathering
the in-place alteration of rocks and minerals. defined as the physical and chemical decomposition and/or disintegration of the mineral constituents of a rock mass by the natural processes of oxidation, reduction, hydration, solution, carbonation, or freeze-thaw.
Two types of weathering
mechanical and chemical
Mechanical weathering
breaks down the rock by either freeze-thaw action or changes in temperature of pressure. As chemical weathering turns minerals to clay, they can absorb enough water to expand and put pressure on the rocks, physically breaking them apart.
Chemical Weathering
alters the internal structure of minerals by the processes of oxidation, carbonation, or hydration. As the surface area of an exposed rock increases through mechanical weathering the opportunities for chemical weathering increase/accelerate.
Hardpan
A hardened impervious layer, typically of clay occurring in or below the soil and impairing drainage and plant growth. Found in the B-Horizon.
What happens when feldspar (the most abundant mineral in the Earth’s crust) reacts with water and weak acids
It decomposed into clay minerals.
What is the main determinant of the products produced by chemical or mechanical weathering
Climate
Dominate weathering in Artic Climate
Frost weathering (mechanical weathering) dominates. Feldspars in granitic rocks are reduced to coarse angular fragments, similar to what you might find in mountainous topography or in tectonically active areas.
Dominate weathering in temperate to semi-arid climates
Mechanical weathering dominates, leaving feldspar-rich sands and a clay fraction of montmorillonite ( a member of the smectite group of expansive minerals) and illite.
Dominate weathering in humid, tropical climates
Chemical weathering dominates. Feldspar is reduced to kaolinite, iron and aluminum hydroxides, and dissolved ions of K, Na, Ca, and Mg (laterite). Pyroxenes and olivines may dissolved completely. Intensely weathered clays from silicates may have lost all silica leaving accumulations of aluminum hydroxides that form bauxites.
Laterite
a clayey soil horizon rich in iron and aluminum oxides, commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red because of the high iron oxide content.
Bauxite
a metalliferous laterite where aluminum is concentrated.
Weathering of pyrite FeS2
is based upon the Eh (oxidation or reduction potential) and pH (the measure of acidity or basicity of a solution) relationship.
Eh is measured how
in the environment in volts using an electrode and comparing it to a theoretically calculated value.
What do Eh and pH indicate?
Eh indicates the ability of the environment to supply electrons, while pH indicate the environment’s ability to supply protons.
Stability of minerals under weathering
Halite
Calcite
Olivine
Anorthite
Pyroxene
Amphibole
Albite
Biotite Mica
Orthoclase
Muscovite Mica
Clay Minerals
Quartz
Aluminum Hydroxides (Gibbsite)
Iron Oxides (Hematite)
pH dependent bacteria that can accelerate the weathering process of pyrite
Thiobacillus ferroxidans
Oxidizing environment
adds oxygen and removes hydrogen and loses electrons through the process.
Reducing environment
oxidation is prevented by removal or oxygen and other oxidizing gases or vapours, and may contain actively reducing gases such as hydrogen, carbon monoxide and gases such as hydrogen sulfide that would be oxidized by any present oxygen.
Dunes
Sand that is piled up as a result of transportation by the wind of sand-sized particles. Often found in back beach areas or desert climates where the topography is relatively flat and the surface sand is dry. Most dunes are composed of a well-sorted sand (SP).
Ripple and ridges
Small-scale features that are usually found on the surfaces of sand deposits resulting from the flow of wind or water over the surface. The shape of the ripple mark can be an indicator of the direction of flow of the wind or water or the depositional environment.
Sand shadows and sand drifts
These two features are similar in that both form as a result of an obstruction in the path of migrating sands. The sand shadow forms behind the obstruction where the velocity of the wind declines causing the sand to drop. Sand drifts develop in the lee (downward side) of a gap where the velocity of the wind declines after passing through the gap.
Sandsheets
Extensive flat areas covered with a coarse-grained sand that does not form dunes, but typically are covered with ripple marks.
Whaleback or sand levees
A very large hill or ridge of sand elongated parallel to the prevailing wind. In general whalebacks do not migrate and can be over 100 miles long, a couple of miles wide and 150 feet high. Undulations are smaller whalebacks.
Loess
Wind-blown silt (ML) that is calcareous, homogeneous, and permeable. Loess covers extensive area s in the Pacific Northwest and Mississippi Valley regions.
API Units
A unit of measurement of gamma rays. API stands for American Petroleum Institute.
ASTM
American Society of Testing and Materials International. ASTM develops numerous standards by consensus and publishes them annually.
Auger
A screwlike boring tool used in relatively unconsolidated near-surface materials. Soil that sticks to the auger gives a good indication of the soil type encountered at the depth penetrated.
Azimuth
For radar images, the dimension parallel to the flight path.
Borehole Geophysics
The science of recording and analyzing measurements of physical properties made in wells or test holes.
Caliper Log
A well log that shows the variations with depth in the diameter of an uncased borehole.
Casing
A heavy metal pipe lowered into a borehole and cemented in place to prevent cave-in, loss of drilling fluid, and unwanted fluids from entering the borehole.
Cone of Depression
A depression in the potentiometric surface of groundwater that has the shape of an inverted cone and develops around a well from which water is being withdrawn. It defines the area of influence of a well.
Cone Penetrometer
A tool consisting of a cone-shaped tip on the end of a hollow steel rod that is pushed into the ground to record resistance to insertion.
CPT
Cone Penetration Test. The test measures the resistance of the cone to penetration and the friction on the rod. Can be correlated to soil type and density in both cohesionless and cohesive soils. Sandy soils have a high cone resistance and low friction ratio; clayey soils have a low cone resistance and high friction ratio.
Drawdown
The amount the water level in a well is lowered due to withdrawal of water.
Dutch Cone
A specific type of Cone Penetrometer.
Gamma Ray Log
The radioactivity log curve of the intensity of natural gamma radiation emitted from the rocks in a borehole. It is commonly used to differentiate between shale (with a high gamma reading) and other sedimentary rocks.
Gravity Survey
A series of measurements made by a gravimeter at a number of different locations in the field to determine the density distribution by evaluating the gravitational pull.
Ground-Penetrating Radar
The application of radar or radio waves to the subsurface using a radar impulse as the source and a receiver. Transmits high frequency radio waves into the ground that are recorded back at the antenna to get an image of subsurface structures or conditions.
Low frequency antennas examine the subsurface at great depths while the higher frequencies are used near the surface.
Ground-penetrating radar can see as deep as 100 feet.
InSAR
Interferometric Synthetic Aperture Radar. A remote sensing method that is sued to study ground deformation, particularly in subsidence, volcanic and fault studies.
Invaded Zone
A transitional zone in a borehole located between the flushed zone and the uninvaded zone. It refers to the degree to which the mud filtrate penetrates the formation fluids, resulting in a transition from the mud filtrate saturation to the formation water saturation.
LiDAR
Light Detection and Ranging. A remote sensing method using laser beams to record topographic changes.
Lysimeter
A device for collecting water from the pore spaces of soils to determine the soluble constituents removed by drainage. It consists of a porous ceramic cup (to withdraw soil pore water) a tube to act as a reservoir and a vacuum assembly to retrieve the sample.
Neutron Log
A radioactivity log curve of the intensity of radiation produced when the rocks in a borehole are bombarded by neutrons. It indicates the presence (but not type) of fluid. It is often used in association with the gamma ray log to distinguish porous and nonporous formations.
Normal-Resistivity Log
A log that makes measurements of the resistivity of formations using 4 electrodes set up in a standard 16- or 64-inch spacing.
are used to determine water quality and to find the saltwater-fresh interface in coastal aquifers.
Are subject to errors unless corrections are made for bed thickness, borehole diameter, mudcake thickness, and fluid invasion.
Packer Test
An aquifer test in which two inflatable seals (or packers) are set in an open borehole to prevent movement of groundwater in the test section while the permeability of the isolated rock is determined.
Percolation (Perc) Test
An in-situ test that determines the suitability of a soil for a sewage disposal system (leachfield). This test made by digging a hole, filling it with water, wand measuring the rate of decline of the water table.
Piezometer
A device that measures in situ pore water pressures, often an open standpipe to monitor water levels in permeable materials, or an enclosed electronic pressure transducer used in impermeable soils.
Pumping Test
A test made by pumping a well for a period of time and observing the change in hydraulic head in the aquifer.
Range
For radar images, the dimension perpendicular to the flight direction.
Resistivity Log
A log that makes quantitative measurements of the specific resistance of a material to the flow of an electric current.
Rippability
The ease with which soil or rock can be excavated mechanically. Initially was based solely on seismic velocity, now parameters such as uniaxial tensile strength, weathering, abrasiveness and spacing of discontinuities are considered to obtain a more representative assessment.
Rotary Drilling
The chief method of drilling deep wells. A drill bit grinds a hole in the rock, and lubrication and cooling are provided by continuously circulating drilling mud which brings the well cuttings to the surface.
Rock Quality Designation (RQD)
A measure of the intactness of rock core, relating to the percentage of intact core to the total core run. defined as the total combined length of all the pieces of intact core that are longer than twice the diameter of the core recovered during the core run divided by the total length of the core run.
Seismic Reflection
A survey method that utilizes the travel times of seismic waves that are reflected back from deep formations giving a detailed picture of subsurface structures.
Shelby Tube
A thin-walled, push-tube sampler that obtains undisturbed samples of cohesive soils. Some level of cohesion is required. Hard, cemented or gravelly soils, or soils too soft or wet, cannot be sampled with this type of sampler.
Single-Point Resistivity Log
A log that measures the resistivity using two electrodes and having a limited area of investigation of from 5 to 10 times the electrode diameter.
Widely used for making lithologic interpretations.
Slug Test
An aquifer test made either by pouring a small charge of water into a well or by removing a slug of water from the well. The removal of water from the well is also called a bail-down test. Used to determine hydraulic oncductiivty and transmissivity, reliability of storage coefficient value is questionable.
Split-Spoon Sampler
A thick-walled barrel sampler that obtains disturbed soil samples and that is used in the Standard Penetration Test.
Spontaneous Potential (SP) Log
A log of the difference in DC voltage between an electrode in a well and an electrode at the surface. The difference in voltage is mostly a result of the electrochemical potentials that develop between borehole fluid, formation water and the surrounding rock materials.
Standard Penetration Test (SPT)
A standardized soil sampling procedure in which a 140-pound hammer is dropped 30 inches, drilling a two-inch split-spoon sampler 18 inches. The blow count to drive the sampler through the last 12 inches is correlated with the soil conditions. The number of blows is related to the density or strength of the soil. Recorded blow counts are affected by the overburden pressure with deeper soils showing greater resistance to being driven and therefore a higher blow count.
Tensiometer
A device sued to measure soil matric potential (soil water suction, or the ability to draw water into the pore spaces). Used to determine irrigation needs and water consumption by plants.
Test Pits
A pit easily dug with a backhoe to obtain bulk samples and to identify subsurface materials in situ. They are useful to differentiate between large boulders and bedrock, to detect soil cracks or fissures, and to determine thickness of shallow units and suitability of borrow materials. Frequently used for fault and landslide investigations.
Only useful for shallow surveys 12 to 15 feet deep.
Well efficiency
The ratio in percent of theoretical drawdown to actual drawdown measured in a well.
Well log
A graphic record of the measured physical characteristics of the subsurface encountered in a well plotted as a function of depth.
Remote Sensing
general term for the collection of images using methods that are not in direct physical contact with the object or location being observed. (Aerial imagery, satellite imagery, infrared detectors, thermal, laser, and radar systems)
Stereo-Paired Low-altitude Aerial Photography (black & white, color) Advantages/Disadvantages
Gives more detailed view of a smaller area. Images may only be taken on clear days, either early or late, to provide shadows to assist in interpretation. Relatively low cost.
Principally used for engineering geologic and environmental investigations; landslides, faults, site histories.
Scale 1:40,000 or larger
High Altitude Aerial Photography (black & white, color) Advantages/Disadvantages
Images don’t show as much detail as they have less resolution, they are much smaller in scale so are only usable for regional studies. Fewer photographs are required to cover an area. Relatively low cost.
Used to map topography, soils, gross geologic features like plunging anticlines, and crop inventories.
Scales 1:80,000 to 1:120,000
Infrared Photography “False Color” (black & white, color) Advantages/Disadvantages
Images will show stressed vegetation as pink to blue before it is visually apparent. Healthy vegetation appears red. Images provide higher contrast and greater resolution than visible color photos.
Used to study landforms, health of vegetation, environmental pollution, and effects of human activities; not to be confused with thermal infrared which takes images at longer wavelengths.
Scales: 1:58,000 to 1:120,000
SLAR - Side-looking Airborne Radar Advantages/Disadvantages
Capable of obtaining data day or night and through the clouds, but the shadows produced may obscure areas.
Often used in areas in which cloud cover is common.
SRTM - Shuttle Radar Topography Mission / SIR - Shuttle Imaging Radar Advantages / Disadvantages
High resolution data available from the USGS for input into GIS. Data control points were precisely located by geodetic surveying. There are voids where data was not collected.
Elevation data used to generate 3-D visualizations of the Earth’s surface show changes due to flooding, erosion, landslides, earthquakes, weather, and climate change. Military uses them for mission planning, rehearsal, modeling, and simulation.
InSAR - (Interferometric Synthetic Aperture Radar) Advantages/Disadvantages
Surveys can be done quickly and cover a large area at a good resolution. Errors can be introduced by atmospheric conditions as well as varying topography. There is no U.S. satellite dedicated to InSAR.
Used for measuring deformation and hazard monitoring such as fault and landslide movement, volcanic activity, and subsidence. Additional uses are tracking ice sheets and groundwater movements.
Landsat (formerly Earth Resources Technology Satellite - ERTS) Advantages / Disadvantages
Open source imagery available in digital format. Uniform prices and priorities.
Samples 11 electromagnetic bands.
Map soils, geology, and the effects of precipitation and evaporation upon the occurrence and character of groundwater.
SPOT (Satellite Pour I’Observation de la Terre also known as Systeme Probatoire d’Observation de la Terre) Advantages / Disadvantages
While expensive, there is a quick turnaround for images (the satellite can be tasked to provide custom images). Resolution is available at various levels down to 2.5 m.
Images are used for different purposes ranging from stereoplotting and detailed radiometric studies, photointerpretation, standard cartographic projection (digital elevation models), thematic studies, and surveillance.
LiDAR (Light Detection and Ranging) Advantages / Disadvantages
It penetrates the canopy and can be used for obtaining details in remote areas. It cannot be used on cloudy or rainy days. Uses a near infrared laser to map topography, while green light is used to measure bathymetry.
Used to collect elevation data as an alternative to field surveys and photographic techniques and is used for fault studies.
NDOP Imagery
Provides complete coverage of the U.S. The intention of the program is to update digital orthoimagery every 3 to 10 years.
NHAP Imagery (National High Altitude Program)
Started in 1978 and ended in 1987. It was run through a number of Federal agencies; their goal was to provide consistent and systematic aerial photograph coverage in the U.S. for the widest variety of users. Two images were taken at 2 different scales, 1:58,000 CIR and 1:80,000 black and white, simultaneously.
NAPP Imagery (National Aerial Photography Program)
Began in 1987, replacing NHAP, with the objective of acquiring complete uniform photo coverage of the conterminous U.S. over a 5 to 7 year cycle. The photography has a scale of 1:40,000 and can be provided in either the black and white or color infrared format.
NRCS Imagery (Natural Resource & Conservation Service) or USFS Imagery (Forest Service (FS) or USFS)
Photos are not generally rectified for scale accuracy. The scales of the negatives range from 1:6,000 to 1:80,000; not all scales are available for all areas. Most of the FS photography is available in color or color infrared. Most of the NRCS imagery is B/W.
NAIP Imagery (National Agriculture Imagery Program)
Aerial imagery is acquired during the growing season. The goal is to make digital orthophotography available to both the public and government agencies within a year. These “leaf-on” photos are taken to provide an indication of the growing conditions. This imagery is used as a base layer for GIS programs.
Electromagnetic Spectrum
light and energy emitted by the sun. Commonly divided into seven regions from shortest to longest wavelengths:
Gamma Rays,
X-rays,
Ultraviolet,
Visible,
Infrared,
Microwave,
Radio.
Visible Light
approximate wavelengths of 400 to 700 nanometers.
Violet has the shortest and red has the longest
ROY G BIV
Blue Light - reflected by water
Green Light - reflected by chlorophyll
Red Light - reflected by iron rich rocks and soils
Infrared Light
Divided into Near Infrared (NIR), Shortwave Infrared (SWIR), Midwave Infrared (MIR), and Longwave or Thermal Infrared (LWIR or TIR). Approximate wavelengths are from 700 nanometers to 15,000 nanometers
Near Infrared (700 to 1100 nanometers)
absorbed by water which highlights land-water boundaries. Plants reflect these wavelengths; the healthier reflect more strongly than stressed plants. This method can penetrate the haze so it is more useful in hot and humid areas.
Shortwave Infrared (1100 to 3000 nanometers)
is useful to distinguish between cloud types and between clouds, snow and ice. The more water there is at the surface and in the soils, the darker the image will appear. Newly burned land reflects well in this wavelength. In Addition, geologic maps can be made based on the different reflected characteristics of the rocks.
Midwave Infrared (3000 to 5000 nanometers)
is used to measure thermal radiation at night, sea surface temperatures, and fires.
(Unnamed) Infrared (6000 to 7000 nanometers)
can track water vapor in the atmosphere, so it is useful for weather forecasts.
Thermal or longwave Infrared (8,000 to 15,000 nanometers)
Images digitally record emitted heats (not reflected heat). As a result, these wavelengths can be detected both day and night. In a black and white thermal image the areas or objects that have a lighter grey or white are warmer than those that are darker or black in the image. Metallic objects, granite, or snow have a low emissivity and so appear cool or dark whereas cement, asphalt, basalt have a higher emissivity and will show up as a lighter tone.
Things that influence emissivity of thermal images
Color (dark images absorb heat have a higher emissivity)
roughness of the surface (rough surfaces absorb heat better)
Moisture content
soil compaction
angle of observation
Common Uses of Aerial photographs
Historical uses of sites for environmental evaluations
Interpreting landslides features and mapping, faults, joints and lineations.
Examining drainage and erosional characteristics for potential impact on engineered structures.
Mapping surficial deposits for potential borrow areas.
Geologic mapping of rock lithology
Delineating soil patters and distributions.
Examining small-scale structural features to determine the presence of traps for petroleum.
Determining general lithology, structure, and physiography for locating ore deposits.
Passive Remote Sensing Technique
rely on sensors to record the energy reflected back from the Earth’s surface. They do not introduce a source of energy such as light or microwaves.
Active Remote Sensing Technique
Introduce a source of energy or light and sensors capture the reflected energy.
(e.g. LiDAR, Radar, SLAR, SRTM, InSAR)
Radar Images
Acquired by sending microwave pulses and the return energy is recorded. Can operate day or night and in all weather, with the ability to penetrate clouds.
Determination of scale
scale =
Focal Length (f) /
Flying height (H)
H
Seismic Refraction
to determine the seismic velocities of the subsurface materials, generally at relatively shallow depths based on the refraction of the waves that occurs at the interface between the different geological materials. The refraction angle is based Snell’s Law relating the angle of incidence and the angle of refraction to the seismic velocities of the two subsurface materials at the interface between the two materials.
Seismic Refraction - Seismograph Geophones
Planted in a linear fashion, at regular intervals with shot points made at each end and sometimes in the middle. Geophones detect the seismic waves triggered at the shot points and the travel time information of the travel time information of the direct wave is transmitted to a seismography to be recorded.
Geophones array should be 4 to 5 times the depth of interest and geophones should be equally spaced. Seismic waves can be generated by hitting a metal plate, dynamite, or dropping a heavy ball.
Ideally the lithologic interfaces are roughly horizontal and there are 3 or fewer interfaces having increasing seismic velocities with depth.
Seismic Refraction - Uses
Engineering geology investigations
determination of shallow subsurface conditions
depth to bedrock
characterize rock type and degree of weathering
locate faults and fractures
stratigraphic mapping
calculate individual subsurface layer depths and thickness
landfill delineation
foundation investigations
rippability surveys
Economic geology investigations
mineral exploration
Mining investigations
petroleum exploration
determining near surface corrections for deep refection investigations
Hydrogeology investigations
depth to water table
hazardous waste site investigations
locating buried channels
Seismic Reflection
to determine the seismic velocities of the subsurface materials, generally at relatively deep depths based on the reflection of the waves at the interface between two rock types. The reflection angle is the same as the angle of incidence.
Direct Wave
the first arriving wave in a seismic refraction survey
Seismic Reflection - Seismogrpah Geophones
method uses a short shot to geophone spacing and can record many interfaces to thousands of feet in depth. Seismic sources and recording devices are similar to seismic refraction surveys though the shot signal is larger due to the depths involved. Shallow work can be done by at much greater expense.
Seismic units of measurement
velocities, feet/sec, or meters/sec
Seismic Reflection Uses
Economic
Petroleum exploration - defining structures at great depth, often under oceans
Ground Penetrating Radar units of measure
MHZ (megahertz)
Ground Penetrating Radar Antenna
Usually in contact with the ground. Transmits short pulses of radio waves into the ground to detect subsurface objects, voids, fractures and a change in geologic units.
The electrical conductivity of the subsurface materials and transmitting frequency limit the applicable depth. Lower frequencies can penetrate deeper, however high frequencies provide better resolution.
Depth penetration reaches a maximum of 30 m in dry sandy soils or massive dry materials such as granite, limestone and concrete,. Clays or high conductivity materials (such as saline groundwater) restrict penetration of the waves from only a few centimeters to 3 m.
Usually mounted on a sled or lawnmower device that can be pushed or towed.
Ground Penetrating Radar Uses
Engineering geology investigations
locate karst-related voids in the subsurface
map geological strata (bedrock)
fractures and voids
site stratigraphy
examine the structural integrity of roads, bridges, and buildings
locate and map re-bar in concrete structures
profile lake and river bottoms
Hydrogeology/environmental investigations
locate and delineate subsurface features
underground storage tanks
buried drums
metallic and nonmetallic utilities and pipes
map landfill boundaries and previously excavated and backfilled areas
delineate and map groundwater table
General geology
identify drilling locations.
Electrical Resistivity Survey
Ability to transmit electrical current through the ground is related to the resistivities of the subsurface materials and the resistivity of the groundwater.
Most minerals, except metallic ores are essentially nonconductive so the measurements are of the pore water characteristics.
Ideal for delineating electrolytic contaminant plumes but can also be sued for locating bulk waste or buried drums, trench limits and locating or following buried utilities.
Electrical Resistivity Survey - Electrical or Direct Current Methods
Measure the bulk resistivity of the subsurface to determine geologic structure and/or physical properties of the geological materials.
Groundwater fluids in saturated or nearly saturated ground regulate the resistivity of the subsurface materials. Freshwater has a higher resistivity while water with a high value of TDS is conductive (low resistiviyt).
Apparent Resistivity
Is the bulk average resistivity of all soils and rock that influence the flow of current.
Electrical Resistivity Survey - Current Source
Electrodes Data acquisition System. The electrodes are planted in the ground linearly at a spacing that is dependent on the lateral extent required and the depth of interest. The wider spaced the electrodes the deeper the view. An additional probe is planted through which the electrical current is transmitted.
An electrical current is introduced directly into the ground through current electrodes. The voltage potential difference is measured between a pair of potential electrodes.
Wenner Array
Electrical Resistivity Survey method used most frequently for engineering and environmental investigations.
Electrical Resistivity Survey - Uses
Engineering geology investigations
map faults
karst voids
Hydrogeology/environmental investigations
characterize subsurface hydrogeology
determine depth to groundwater
map stratigraphy
map clay aquitards
map salt-water intrusion
map vertical extent of certain types of soil and groundwater contamination
estimate landfill thickness
map lateral extent of conductive contaminant plumes
delineate disposal areas
aid is siting wells.
Magnetic Surveys
Measures variations in the magnetic field by determining the magnetic character of the ferromagnetic minerals in terms of the intensity and orientation of the magnetization in the Earth’s field.
Records both remnant magnetization from the existing magnetic filed (flux) and the strength of induced magnetism from an external magnetic filed.
Usually more pronounced in igneous rocks; sedimentary rocks are generally not magnetic.
Magnetic Survey - Unit of measure
The unit of measure for magnetic anomaly maps is the nT or nanoTesla, which is the magnetic flux density.
Magnetic Survey - Uses
Allows evaluation to a greater depth for ferrous objects, makes an ideal tool to detect steel barrels in the subsurface.
Hydrogeology/environmental investigations
locate buried steel drums and tanks
Economic geology investigations
geologic features
mineralized bedrock fractures
igneous intrusions
ore bodies
locating rails in abandoned mines
Gravity Surveys
Gravity measurements detect changes in the earth’s gravitational field caused by variations in the density of the soil or rock or engineered structures. Useful for mineral and petroleum exploration, regional geophysical surveys, and measurement of the geoid.
Bouguer Anomaly
the difference between the observed gravity measurement’s and the theoretical gravity.
Gravity surveys require a number of corrections to obtain the Bouguer Anomaly
Bouguer anomaly basic equation
= observed gravity - latitude correction + free air correction - terrain correction
Free Air Correction
compensates for the altitude of the recording device above sea level. Gravitational attraction decreases with elevation.
Bouguer Correction
Corrects for variations in density of the Earth’s materials. A correction is applied using a constant and applying it to the specific graivity of the rock and the difference in elevation between the topography and sea level.
Latitude Correction
Corrects for the shape of the Earth. The earth is not round and the gravity increases with higher latitudes because of diameter of the Earth is greater at the equator than it is at the poles.
Topographic (Terrain) Correction
Corrects for the decrease in gravitational attraction due to the distance form the center of the Earth and greater density of materials that make up the higher elevation areas. This is computes using a planar base with mountains causing a positive correction and valleys causing a negative correction.
Tidal Correction
Corrects for the variations in background values related to the pull associated with the relative positions of the Earth, sun and moon.
Gravimeter Unit of measure
milligals ( the unit acceleration of gravity of 1 cm/sec^2 is called a gal, a milligal (mgal is one thousandth of a gal)
Gravity Surveys - Uses
Engineering geology investigations
locate and characterized buried bedrock channels and bedrock structural features
detect voids, caves, and abandoned mines or tunnels
geological mapping - used on a regional scale for mappin the subsurface geology
geotechnical studies - mapping subsurface cavities
Economic geology investigations
petroleum exploration - used on a regional scale for mapping sedimentary basins
coal exploration - mapping of coal beds within sedimentary basins
mineral exploration - reconnaissance and direct indication of deposits
Hydrogeology/environmental investigations
mapping of groundwater
Spontaneous Potential - Units of measure
millivolts, measured increases to the left, run together with resistivity
deflections are negative to the left and positive to the right.
Spontaneous Potential - Uses
determining correlating lithology
establishing or confirming bed thickness
determining salinity of formation water
Resistivity - Units of measure
Ohm - Meters, increases to the right, run together on the same tool as SP
Resistivity - Uses
making lithologic interpretations
identifying water quality
locating the fresh water - salt water interface in coastal aquifers
determining hydrocarbon saturation in oil and gas wells
Neutron - Units of measure
% porosity, measured as increases to the left
Neutron - Uses
measuring porosity in petroleum and hydrogeology investigations
Gamma - Units of measure
API, measures naturally occurring radioactivity, increases to the right
Gamma - Uses
Determining shale content of formation
correlating stratigrpahy and lithology
evaluating of radioactive deposits
Density (Gamma-Gamma) - Units of measure
grams/centimeter^3 or kilograms/meter^3 or porosity units
Density (Gamma-Gamma) - Uses
measuring density of the rocks and is used to determine porosity
Sonic - units of measure
milliseconds/ft, acoustic logs
Sonic - Uses
Measuring the transit time of the formation to determine porosity
correlating units and facies analysis
mineral exploration for iron, hydrocarbons and potassium
Spontaneous Potential Curve Deflection (standard case)
Negative to the left and positive to the right. When the formation water is more saline than the drilling mud the deflection is to the left, if the relationship is reversed deflection is mirror image to the right.
Shale line or baseline
A line drawn through the extreme positive deflections on the SP curve for standard salinity relationships
Sand line
A line drawn through the extreme negative deflections
Electrical Resistivity
The ability of a substance to impede the flow of electrical current through itself. The greater the porosity and amount of formation water, the lower the resistivity.
Resistivity is the inverse of conductivity.
In most rocks the porosity and chemistry of the water filling the pores is of greater importance to the resistivity value measured than the composition of the rock matrix.
Most important factor in determining resistivity
The salinity of the water in the pores.
Values of R for evaporites and coal
Can be greater than 1000 ohm-meters because they are impervious and have very low porosity.
Why Tertiary Age sediments have anomalously high Resistivity
These sediments were deposited mainly in fresh water.
What are does a short-normal probe investigate
invaded zone
What are does a long-normal probe investigate
the invaded zone and formation water
How to differentiate between Coal and limestone on log curve
SP/Res curve is not a good answer since both exhibit low SP and very high resistivity. Therefore a density log would show a difference since coal is not very dense and limestone is extremely dense.
A mineral is defined as
a solid inorganic substance of natural occurrence
How are minerals defined
by means of their physical or chemical characteristics. Physical characteristics are a direct result of their chemical composition.
Physical characteristics that can be used to identify a mineral
crystal habit and symmetry
cleavage
fracture
crystal twinning
specific gravity
color and streak
luster
luminescence
radioactivity
magnetism
How are silicate minerals classified
on the basis of the configuration of anions in the mineral structure.
Shape of the silicate molecule
tetrahedron with four large oxygen atoms surrounding a silicon atom.
What are the seven types of silicate minerals?
Nesosilicates
Sorosilicates
Cyclosilicates
Inosilicates
Inosilicates
Phyllosilicates
Tectosilicates
Nesosilicates
Contains SiO4; composed of an isolated tetrahedral
includes zircon, olivine, and garnet
Sorosilicates
Contains Si2O7; isolated double or linked tetrahedral
includes lawsonite and hemimorphite
Cyclosilicates
Contains SiO3
Includes beryl group and tourmaline
Inosilicates (single-chain)
contains Si03
includes pyroxene group and pyroxenoid group
Inosilicates (double-chain)
Contains Si4O11
Includes amphibole group
Phyllosilicates
Contains Si2O5; forms sheets
includes biotite, talc and chlorite
Tectosilicates
Contains SiO2 and Si3O8; forms frameworks
includes feldspar and zeolite groups
Igneous Rocks - modes of occurrence
intrusive (plutonic) or extrusive (volcanic), or hypabyssal
Intrusive Rocks
Coarse grained rocks that are formed by slowly cooling magma far below the earth’s surface
Extrusive rocks
Smooth and fine-grained rocks that are formed by faster cooling magma at or above the earth’s surface
Hypabyssal Rocks
Less common rocks that are formed only slightly below the earth’s surface.
Igneous Rocks Texture Classification
Phaneritic or Aphanitic
Phaneritic
Igneous rock in which crystal structure can be identified megascopically (by the naked eye).
fine-grained < 1mm
medium-grained 1mm - 5mm
Generally intrusive
Aphanitic
Fine-grained igneous rocks in which mineralogy cannot be determined megascopically (by the naked eye)
Generally extrusive
Discontinuous reaction series
Olivine
Mg pyroxene
Mg-Ca pyroxene
Amphibole
Biotite
Potassium Feldspar
Muscovite
Quartz
Sedimentary Rocks can be deposited
physically, chemically or biologically
Three main categories of sedimentary rocks
-Detrital sedimentary rocks, consisting of loose materials derived from erosion
-chemical and biochemical rocks, made up of precipitated minerals
-diagenetic sedimentary rocks, formed as a result of recrystallization, replacement, or other chemical modifications of the original sediments.
How much of the continental surface do sedimentary rocks cover?
comprise less than 10% of the earth’s crust by volume, but cover 75% of the continental surface.
What is the most abundant sedimentary rock
Mudrocks, making up 65% of all sedimentary rocks.
Percent breakdown of sedimentary rocks
Mudrocks, making up 65%
Sandstones make up to 20 to 25%
Carbonate rocks make up 10 to 15%
Diagenesis
Any change occurring within sediment after its deposition and during and after its lithification, exclusive of weathering. Includes the processes of compaction, cementation, replacement, and crystallization, under normal surficial conditions of pressure and temperature.
What are not considered diagenetic processes
Weathering and metamorphism as they do not occur between 100 and 300 C
Cementation
Process by which coarse clastic sediments become lithified or consolidated into hard, compact rocks, usually through deposition or precipitation of minerals in the spaces among the individual grains of the sediment
Replacement
Change in composition of a mineral or mineral aggregate, presumably accomplished by diffusion of new material in and old material out without breakdown of the solid state.
Facies
Broad term referring to such aspects of rock units as rock type, mode of origin, composition, fossil content, or environment of deposition.
facies chagne
refers to a lateral or vertical variation in the lithologic or paleontologic characteristics of contemporaneous sedimentary deposits. It is caused by, or reflects, a change in the depositional environment.
Make occur vertically with time or laterally over as a result of changing environments with distance at the same time.
Difference between conglomerate and breccia
Conglomerates are made up of 50% or more rounded pebbles, cobbles, or boulders whereas sedimentary breccias are made up of 50% or more angular pebble, cobble, or boulder sized fragments
Detrital Rock Examples
Conglomerates, breccias, sandstones, siltstones and claystones
Dolomite
known chemically as CaMg(CO3)2, forms when the porewaters in limestone are enriched through evaporation which causes magnesium to be subsequently exchanged for calcium in the atomic structure.
Diatomite
a light-colored soft friable siliceous sedimentary rock consisting chiefly of diatoms, occurs through thick accumulations of diatomaceous material
Chert
a hard, dense, dull to semivitreous, microcrystalline or cryptocrystalline sedimentary rock, consisting dominantly of interlocking crystals of quartz. Chert may also contain amorphous silica (opal)
Clastic Limestone
Made up of calcium carbonate fragments that were deposited in place or were transported from elsewhere withihn the basin in which they formed.
Classification of chemically and biologically precipitated particles
Oolites are from 0.2 to 2.0 mm, pellets are particles <2.0 mm, and fossils with no size.
Calcirudites
is a type of limestone that is composed predominantly, more than 50 percent, of carbonate grains that are larger in size than sand (2 mm in diameter). The grains can consist of either fragments of fossils, fragments of older limestones and dolomites, other carbonate grains, or some combination of these.
calcarenites
is a type of limestone that is composed predominantly, more than 50 percent, of detrital (transported) sand-size (0.0625 to 2 mm in diameter), carbonate grains. The grains consist of sand-size grains of either corals, shells, ooids, intraclasts, pellets, fragments of older limestones and dolomites, other carbonate grains, or some combination of these.
calcilutites
also known as cementstone, is a type of limestone that is composed of predominantly, more than 50 percent, of either clay-size or both silt-size and clay-size detrital (transported) carbonate grains. These grains consist either of fossil fragments, ooids, intraclasts, pellets, other grains, or some combination of them.
Nonclasstic limestones
Consists of chemically or biologically precipitated calcite or aragonite material that has not been transported since original deposition.
Aragonite
is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, CaCO3.. It is formed by biological and physical processes, including precipitation from marine and freshwater environments.
stromatolite
reef limestone, that are created mainly by photosynthetic microorganisms such as cyanobacteria, sulfate-reducing bacteria, and Pseudomonadota (formerly proteobacteria). These microorganisms produce adhesive compounds that cement sand and other rocky materials to form mineral “microbial mats”. In turn, these mats build up layer by layer, growing gradually over time. A stromatolite may grow to a meter or more. Although they are rare today, fossilized stromatolites provide records of ancient life on Earth.
Three major subclasses of metamorphic rocks
Dislocation Metamorphism
Contact Zones around igneous intrusions
Metamorphosed regionally during mountain building
Contactites
Form when hot magma is intruded into relatively cooler host rocks, heating and metamorphosing the surrounding country rock.
Dislocation Metamorphism
concentrated along narrow belts of shearing or crushing without an appreciable rise in temperature (fault Zones)
Nearly all gamma rays are emitted by what
K40, U238 and Th232
The amount of radiation increases by rock type
anhydrite gypsum < gabbro and basalt < coal < limestone and dolomite < sandstone < shale < arkose < granite
Coal, limestone and dolomite may contain uranium deposits and thus have a higher gamma ray count than expected. Formations with volcanic ash will also give a higher reading.
What is a gamma ray log generally used for?
to determine the shale content of the formations, because radioactive elements tend to concentrate in clays and shales.
Name of the probe used by gamma ray log
scintillation detector - a laboratory grown crystal that produces flashes of light when radiated. These light pulses are used to determine gamma radiation. The more pulses of light the more gamma radiation.
In groundwater applications, gamma rays are measured how?
In counts per second, counts per minute or pulses.
Gamma Ray area of investigation
6 to 12 inches from the borehole wall, area of investigation is also dependent on the energy of radiation measured, density of material, and the probe design.
Neutron log interactions are due to…
the amount of hydrogen present which in turn is due to the water content of the rocks. The greater the hydrogen content, the smaller the volume of investigation of the probe.
Radioisotope when exposed to a neutron source
Will emit alpha particles which bombard the source and produce neutrons.
Most common neutron source
a mixture of beryllium and americium
Three types of neutorn detectors
lithium-iodide crystals
helium-3 tubes
sodium-iodide crystals
Epithermal neutrons energies
0.1 to 100 electron volts, and as energy is lost even further they become thermal neutrons (0.025 electron volts)
Loss of neutron energy
is called moderation and the elements that cause that loss are called moderators
hydrogen is the most effective element in moderating neutrons because it has the same mass as a neutron.
Calibration of all neutron logging equipment
is based on marble and limestone in a pit in Houston, Texas
Neutron logs are affected by…
variations in borehole diameter
thickness of mudcake
salinity of borehole and interstitial fluids
weight of the drilling mud
casing thickness and cement
temperature and pressure
composition of the rock matrix
Neutron log for gypsum or coal
not diagnostic, a neutron log will produce large deflections in the neutron curve to the left, hydrogen in coal is not in the form of water and the gypsum has water of crystallization.
Caliper probe
has three arms that are spaced 120 degrees apart and coupled together and attached to a potentiometer.
Potentiometer
measures changes in resistance which re recorded as voltage changes. The change in resistance is proportional to the average borehole diameter. The caliper probes are calibrated so that 1 inch of chart = 1 inch of borehole.
What does the seismic method indirectly examine
Strength of rocks and their suitability for foundations, pressure zones and discontinuities within the rock. It can often be used to locate the depth to bedrock and to provide a preliminary assessment of the rippability of earth materials.
Revised rippability classification
Uses 5 Classes with 1 being less than 5. A class 1 classification requires light machinery while a class 5 will require blasting.
Snell’s Law
= v1/v2 = sin a / sin b
=
Ground Penetrating Radar
a nondestructive and cost-effective method used to measure changes in the dielectric properties of subsurface materials. It can be used in a variety of subsurface materials including rock, soil, and ice along with engineered materials such as pavement or concrete to detect buried objects, changes, in the subsurface materials and voids
Similar to seismic reflection, except electromagnetic energy is used instead of acoustic energy.
Flux
is proportional to the ferrous mass, ambient magnetic field, magnetic susceptibility and remnant magnetization.
gravimeter
Measures density variations which conform to changes in the earth’s gravitational field.
Relative gravimeter
The most common and is used for gravity surveys conducted by airplanes or ships covering a large area, is compact and contains a spring carrying a weight that is shifted out of equilibrium when gravity changes.
Absolute gravimeter
Measures the force needed to return a falling mass to equilibrium.
Annulus
The space between the pipe and the borehole wall; a ring shape.
Blowout
Uncontrolled flow of gas or fluids from a well.
Fracing or Facking
Using high pressure fluids to fracture in-place rocks to allow for more permeability in tight formations to withdraw oil and gas.
Packer
An expanding device used to isolate particular areas in a well for testing.
Tremie
A pipe used to place grout underwater.
Tripping
The act of removing the drilling rod from the borehole and putting it back in (a round trip)
Shallow boreholes are useful for…
determining soil types, soil thickness, or depth to shallow groundwater.
Flight Augers
mechanically driven augers that are rotated and pushed downward into the earth and do not stay in the hole during sampling. This results in disturbed samples/ therefore strength or compressibility test cannot be performed.
Hollow-stem augers
allow a soil sampler to be inserted through the middle of the rod for sampling without removing the augers. These samples may be sent to a lab for a variety of test such as shear strength, composition, and Atterberg limits. Since drilling fluids are not generally used there is no interference with the groundwater.
Rotary-wash drilling
A method that relies on the rotation of the drilling bit and removal of cuttings from the hole by circulating drilling fluid. Soil classification is done by visual inspection of the cuttings as well as by equipment and drilling rate changes.
Montmorillonitic Clay (bentonite)
used to prevent cave-in of loose cohesionless soils or soils below the water table
Air Rotary
Air or foam is used through the drill stem to bring the cuttings to the surface around the outside of the drill stem.
Can be used to depths of 1000 feet or more and the hole can be advanced quickly.
Problematic for contaminant investigations when foam is added because it introduces foreign materials.
Mud Rotary
Water or drilling mud circulated through the drill stem is used to bring the cuttings to the surface in the annular space between the borehole wall and drill wall.
Used for boreholes in which a geophysical log needs to be run, get rock core samples and can be drilled to great depths.
Advantage is that the hole will remain open after the drill stem has been removed, while a drawback is that the drilling fluid can penetrate the formations changing the groundwater chemistry.
Reverse Rotary
Drilling fluids are added to the borehole through the annular space between the borehole wall and the drill stem and then suction draws the cuttings up the drill stem.
Has an advantage over mud rotary due to the velocity in which the cuttings are brought to the surface through the suction pump. Requires little if any drilling additives and a minimum borehole diameter of 12 inches.
Much more expensive than air or mud rotary methods.
Shutter Ridge
a ridge which has moved along a fault line, blocking or diverting drainage. Typically, a shutter ridge creates a valley corresponding to the alignment of the fault that produces it. Shutter ridges occur exclusively at strike-slip faults.
Bucket Auger
A large-diameter bucket (18 to 48 inches) collects material that is excavated using a auger-type bit that fills the bucket with material. The bucket is then brought to the surface and dumped, leaving an open hole. Works best in clayey formations as materials must be able to stand in an open hole.
Percussion Drilling Methods / Cable Tool
Borehole advancement is accomplished by using cable to drive the bit. the cable lifts and drops a heavy drill string or a hammer type of device called drilling jars to break up the subsurface materials. After the soil and rock materials are broken up they are removed with a bailer. If the hole is above the water table, water must be added to make a slurry for the bailer to work. Casing is installed as the hole is advanced. “The oldest drilling method, Slow and expensive because it is labor intensive”
Sonic Methods
Borehole advancement and continuous sampling of disturbed samples is through a process where the rod and sampler are vibrated through the ground at frequencies between 50 and 180 Hz. It is useful for a wide range of soil types including soils with large particles that are very difficult to sample. Can drill at any angle and drilling fluids can be used but are not required.
Piezocone (CPTU)
A standard penetrometer with the ability to measure porewater pressures.
Electric Conductivity Cone
A device that measures the conductivity of the subsurface materials. Use to evaluate the thickness of the capillary fringe, depth to the water table and more importantly the degree of contamination. The dissolved solids and the acidity (pH) indicate the presence of contaminants such as nitrates, sulfates, Ca, Mg, Na, Cl, and Fe as well as heavy metals.
Environmental Cone
A device with a cavity that collects and tests water in a nitrogen environment. Determines pH, re-dox potential and temperature.
Hydrocarbon Cone
A cone with a UV light source that detects fluorescence by a photomultiplier tube. Hydrocarbons fluoresce in the presence of UV light allowing free prodcut to be detected.
Cone Pressuremeter
Has an inflatable section that is implmented during a pause in the advancement of the cone to determine the shear modulus. Measures soil strength and stiffness, undrained shear strength in clays, relative density in sands, and shear modulus of the subsurface materials.
Gamma Cone
Measures naturally occurring radiation. Because of the variations of radiation occurring in the various subsurface materials this tool is instrumental in lithologic mapping and stratigraphic correlation.
Seismic Cone
Measures shear wave velocity and gives the strain shear modulus and constrained modulus, used in conjunction with a seismography and a seismic wave generating device. Analysis of the moduli allows the prediction of ground surface motions from earthquakes, evaluation of the impact on foundations by the use of vibrating equipment and anticipated deformation adjacent ot excavations, and the impact of wave loading on offshore structures.
Soil moisture probe (SMP)
A device located above the CPT device that consists of 2 isolated electrodes and an electric circuit that records the characteristics between the electrodes. Can obtain soil moisture properties like electrical conductance and therefore resistivity, capacitance, the dielectric properties. NAPL’s have dielectric properties different from water and can be differentiated using this device.
Purpose of using drilling fluids
-Bringing cuttings up
-Preventing borehole collapse / accumulation of cuttings on the borehole wall
-Preventing or reducing fluid loss or gain to or from the formation
-Reducing interactions of the drilling fluids with the formation
-Prevent swelling
-Keeping the drill bit and rod cool and lubricated
-Controlling the downhole pressure heads to prevent heaving or blowouts
Seal the formation
Using drilling fluids to prevent or reduce fluid loss or gain to or from the formation
What is colloidal clay?
Bentonite
Polymer (revert) drilling mud weakness
Low gel strength so cuttings drop out faster. Some polymers can’t be used in particular situations due to bacteriological problems or chemical interactions.
What is barite and its use case?
Barium sulfate adds substantial density to drilling fluids to prevent the borehole from collapsing or taking on water from the formation.
Calcium carbonate as a drilling fluid additive
a bridging agent
Calcium chloride/sodium chloride as a drilling fluid additive
may be used to add weight but is also used when temperatures are below freezing. Weakness is that it will cause a viscosity loss in bentonite fluids.
Calcium chloride / potassium chloride as adrilling fluid additive
inhibits reactions with shale
Oil or synthetic based mud
Used principally for petroleum drilling.
What are the appropriate conditions for a split spoon sampler for (SPT) (Driven Sampler)
Saturated or unsaturated soft to stiff clay, silt and sand. Results in a disturbed soil sample.
What are the appropriate conditions for a Shelby Tube sampler (push sampler)
Saturated soft clay and interbedded silts and sands, superior for firm clays that are either unsaturated or saturated. Results in an undisturbed sample.
What are the appropriate conditions for a Osterberg (Hydraulically) or Hvorslev (Mechanical) push samplers?
Designed for both saturated and unsaturated cohesionless sands and soft wet clays such as bay muds or lake bed deposits. Results in undisturbed soil sample.
Difference between Osterberg and Hvorslev sampler?
Osterberg - Hydraulically activated piston
Hvorslev - Mechanically activated piston
What are the appropriate conditions for the Pitcher Barrel sampler? (Modified push drill samplers, double tube sampler)
Acceptable in all saturated and unsaturated soil materials except gravels and superior in interbedded silts and sands. Results in an undisturbed soil sample.
What are the appropriate conditions for the Denison sampler? (Modified push-drill samplers, double tube sampler)
Acceptable in both saturated and unsaturated silts and sands, superior in clays. Results in an undisturbed soil sample.
Driven Samplers
Widely available since sampler is compatible with commonly used drilling rod diameter. Can yield disturbed and undisturbed soil samples depending on barrel sample wall size and diameter. Undisturbed samples are obtained by samplers with thin walls and high ratio of inside diameter to wall thickness.
Sample is removed by splitting the barrel or removal of a liner.
What can a disturbed sample be used for?
General characterization, grain size distribution, or attenberg limits.
What can undisurbed sample be used for?
Shear strength, compressibility, compaction and consolidation characteristics.
Three ways to obtain an undisturbed soil sample
Thin-walled or push-tube samplers (Shelby Tube)
Piston Samplers
Double-tube samplers
Thin-walled push-tube samplers size
normally have a 3-inch or 5-inch o.d. and thickness of 14-gauge or 11-gauge, respectively. The thinner the wall, the better the samples obtained. (e.g. shelby tube). The sample is removed by hydraulically pushing it out.
What should you do after recovering a push-tube sampler?
Measure the length and compare to the length of push to determine percent recovery and determine if consolidation or sloughing occurred during sampling. If the sample length is shorter than the push length, the soil may have been compressed or fell out during removal of the sample. If longer the then the sample may have sloughed into the borehole.
Fixed-Piston Samplers
A thin-walled cylindrical tube is forced into undisturbed soil in a continuous push without rotation. Pressure is applied throughout the drill stem to push the inner sample head and sample tube. When sampling has fully penetrated the soil the pressure is relived and the sampler is rotated to shear off the sample at the bottom of the tube. Drilling mud and fluids are maintained at the top of the hole to maintain suction and successful sample recovery. Sample tubes are generally 3 in i.d. by 3 3/4 in o.d. or 5 in i.d. by 5 3/4 in o.d.
What are fixed-piston push samplers primarily used for?
To take samples below the water table. They work best in cohesionless sands and soft wet soils. Hard, cemented or gravelly soils are too hard to penetrate using the piston sampler. Also lots of moving parts which complicates sampling.
What are two types of fixed-pistons push samplers?
Mechanically activated types (Hvorslev and Butters)
Hydraulically activated types (Osterberg and modified Osterberg)
Double-tube Core Barrel Samplers
Used to sample fine-grained, uncemented, or slightly cemented soils. If drilling is performed carefully in slightly cohesive soils, an undisturbed sample is possible. The samplers are not suitable for gravelly soils, cohesionless sands with low unit weights and loose silts below the water table, very soft and plastic cohesive soils, or materials that are fractured or fissured.
Two main types of double tube samplers
Denison
Pitcher
Denison sampler
Has an outer barrel with cutting teeth on the bottom, an inner barrel with a smooth cutting shoe, a spring core catcher, and a liner. The outer barrel rotates around the stationary inner barrel and advances the sampler. The liner has an i.d. of 5 7/8 in and is 24 inches long. Its purpose is to hold the sample and assist in transport. Drilling fluid circulates through vents in the inner barrel. The sampler can obtain samples of hard or cemented soils.
Pitcher sampler
the inner barrel extends ahead of the bit and is loaded with a spring that allows it to conform to the soil stiffness. If the soil is too hard to be penetrated, the spring retracts the inner barrel and the bit moves down even with the end of the tube and cuts as the tube fills. The barrel is rotary driven and the inside diameter of the sample is from 4 to 6 inches.
What is the ASTM test procedure for the SPT
ASTM D-1586
What do 0-4 SPT blows tell about a sand and silt soil type?
Very Loose
What do 30-50 SPT blows tell about a sand and silt soil type?
Dense
What do 0-2 SPT blows tell about a clay consistency?
Very Soft - Easily penetrated a few inches with fist.
What do 15-30 blows tell about a clay consistency?
Very stiff - Readily indented with thumb nail.
Boring Log minimum requirements
- A location sketch, including notes and distances to map, and the ground surface elevation at the hole.
- The job location, name, date, number and boring number.
- The drilling company, drillers’ names, and type of drill rig.
- Type of sampler used, hammer weight and fall for driven samples or pressures required to obtain push samples, and sample condition.
- Water levels when first encountereed, measured daily during the hole dvancement, and upon completion.
- Completion status indicating grout intervals, backfill materials and method, monitoring equipment installed and perforation intervals.
- A detailed soil or rock description.
What should a soil boring log include
detailed soil description with color, soil classification using the Unified Soil Classification System (USCS) symbol, moisture content, strength, and structure.
What is soil strength?
consistency or relative density
How should soil color be described?
at the natural moisture content and in comparison to some commonly used standard color char such as the Munsell Soil Color Chart.
Field estiamtes of the moisture content
Are approximate and use the following general terms - Dry, Moist, Wet, Saturated.
How is soil strength (relative density or consistency) estimated?
Relative to the blow count from a SPT. Relative density is used for all coarse-grained soils and term consistency is sued for all fine-grained soils.
Field measurement for coarse-grained soils
100% of the sample passes the 3-inch sieve and less than 50% passes the #200 sieve.
Field measurement for fine-grained soils
more than 50% passes the #200 sieve
Homogenous Soil characteristic
uniform properties throughout
Heterogeneous Soil Characteristic
Dissimilar properties
Stratified Soil Characteristic
Alternating layers of different types or colors of soil
Laminated Soil Characteristic
Alternating layers less than 1/8 to 1/4 inch thick
Fissured Soil Characteristic
Tendency to shear along definite fracture planes with little resistance; fractures may be a result of shrinkage and are often filled with fine sand or silt.
Honeycombed Soil Characteristic
Contains many holes
Slickensided Soil Characteristic
Soils which are slick, glossy, polished, and/or grooved on the surfaces of fractures or soil particles, generally constituting planes of weakness.
Blocky Soil Characteristic
Easily broken into small angular lumps which are difficult to further break down
Lensed Soil Characteristic
Containing thin, discontinuous beds or small pockets of different material.
Caliche Soil Characteristic
Secondary calcium carbonate forming a horizon that is typically very hard or well cemented.
Useful soil material descriptors
-estimates of percentages of gravel, sand and fines
-the maximum size of the particles
-grain shape of coarse-grained component (angularity)
-coating or staining of particles
-plasticity
-organic content
-type and degree of cementation
Useful observations about drilling operations
-drilling methods used
-pressures recorded
-color of return circulation
-grain or loss circulation
-drilling difficulties
-overnight slough
-morning water levels
-drillers’ comments
What are useful drilling comments when completing a hole
-total depth
-reason for stopping the hole and completion status
-installation of water monitoring or pump equipment
-backfill grout and any open hole testing
Rock coring
utilizes a rotary-wash drilling method and performed when it is necessary to obtain continuous samples. Similar to the Pitcher barrel sampler and is drilled into the rock with special core samplers made from hardened steel alloys, or diamond chip bits.
Standard Drill bit size from small to large
EW - 13/16 Core Diameter 1 1/2’ Hole Diameter
AW - 1 3/16 Core Diameter 1 7/8’ Hole Diameter
BW - 1 5/8 Core Diameter 2 3/8’ Hole Diameter
NW - 2 1/8 Core Diameter 3” Hole Diameter
2 3/4 x 3 7/8 - 2 11/16 Core Diameter 3 7/8” Hole Diameter
HW - 3 Core Diameter 3 7/8” Hole Diameter
First Letter designates size of the hole and second letter indicates the group of compatible drill rods, casing, etc.
Rock Boring Logs
necessary to make an accurate interpretation, we need to identify sections with poor recovery which will require an interpretation of the subsurface geology.
Rock descriptions include
detailed rock type, color, hardness, mineralogy, textural and structural features and any other features that might aid in correlation and/or interpretation of the geology.
Also run length, recovery and Rock Quality Designation (RQD)
Fugitive data
data which would be lost if not documented during the drilling process. Would include drilling rate, drilling methods, drilling pressures, color of return fluid, loss or gain of circulation, drilling difficulties, drillers’ opinions, rig actions, bit changes, drilling muds (types and quantities) etc.
Lightness
range from light or white to dark or black
Chroma
the color saturation which would range from a very pale to vivid
Hue
the color, Munsell Rock Color Chart helps ensure consistency of color names
Hardness categories for rock boring logs
Soft - plastic material
Friable - easily crumbled or reduced to powder by the fingers
Low Hardness - can be gouged deeply or carved with a pocket knife
Moderately Hard - Can be readily scratched by a knife blade, scratch leaves heavy trace of dust
Hard - can be scratched with difficulty, scratch produces little powder and is faintly visible
Very Hard - cannot be scratched by a knife blade
porphyritic
a type of texture occurring in volcanic and intrusive igneous rocks defined by the presence of larger crystals, called phenocryst
can be intrusive or extrusive
phenocryst
an early forming, relatively large and usually conspicuous crystal distinctly larger than the grains of the rock groundmass of an igneous rock
Modified Wentworth Scale
Used to differentiate sedimentary rock grain sizes.
Gravel - 2mm - >256 mm (conglomerate/ breccia rock
Sand - 1/16 - 2 mm (sandstone)
Mud - < 1/256 - 1/16mm (siltstone, claystone, mudstone, shale)
lineation
the arrangement of grains may show a preferred orientation
Foliation
a general term used to describe platy, layered or planar fabric metamorphic rocks.
Quantitative terms used in describing layered sedimentary rocks
Massive - Very thick bedded > 4 ft
Blocky - thick bedded 2-4 ft
Slabby - thin bedded 0.2-2 ft
Flaggy - very thin bedded 0.05 to 0.2 ft
Shaly or Platy - laminated 0.01 to 0.05 ft
Papery - thinly laminated < 0.01 ft
Terms for angularity and roundness
very angular, angular, sub-angular, sub-rounded, rounded and well rounded. These are the assumed weathering pathways from the original discoidal, prismatic, or spherical shapes.
Textural features used to describe rock specimines
- Grain or crystal size
- Grain or crystal shape
- Lineation
- Bedding and foliation
- Grading/sorting
Grading
refers to the range of particle sizes
Sorting
refers to the degree to which the particle sizes are differentiated
How do engineering geologists and geotechnical engineers describe rock and soil?
In terms of grading
Fresh - weathering descriptor
rock shows no discoloration, loss of strength or any other effect due to weathering.
slightly weathered - weathering descriptor
the rock is slightly discolored, but not noticeably lower in strength than fresh rock
Moderately Weathered - weathering descriptor
the rock is discolored and noticeably weakened, 2-inch diameter core can’t usually be broken by hand across the rock fabric.
Deeply Weathered - weathering descriptor
the rock is usually discolored and weakened to such an extent that the 2-inch diameter core can be readily broken across the rock fabric.
Extremely Weathered - weathering descriptor
rock is discolored and is entirely changed to a soil but the original fabric of the rock is usually preserved. Soil properties depend on the composition and structure of the parent rock.
Fractures
include joints, shears, faults or other continuous breaks in the rock and tend to reduce the overall mass hardness and strength of the rock.
Joints
fractures along which there has been no relative movement of the rock on either side of the fracture.
Quantity of fractures are expressed how
in terms of fractures per foot
How are fracture surfaces described
planar, undulating or stepped and rough, smooth or slickensided.
Fracture Spacing
Described as crushed, intensely fracture, closely fractured, moderately fractured, little fractured or massive fractured.
RQD designations
0-25% - Very Poor
25-30% - Poor
30-75% - Fair
75-90% - Good
90-100% - Excellent
Vane Shear tests
measured using a device with 4 flat metal blades fixed at 90 degrees to each other attached to a metal rod that is pushed into the soil and rotated. The rotational torque values at soil failure indicate the in-situ undrained shear strength and sensitivity of cohesive fine-grained soils.
ASTM D1556
Sand Cone Density Test
Sand Cone Density Test
An apparatus consisting of a gallon jug and cone that measures the volume of a small hole which can be compared to the weight of the soil material removed and dried to determine the moisture content. This value is then compared to the compaction cure developed in the lab to get a relative compaction.
Nuclear Density Test ASTM Number
ASTM D6938 - 17a
Nuclear Density Test
Using a nuclear density gauge a probe that emits gamma rays into the subsurface is inserted into the ground and measurements are recorded of the backscattered rays which are proportional to the density. After drying a sample of the tested material the moisture content is determined. The calculated dry density is then compared to the lab generated compaction cure.
how is compaction % calculated
dry density / maximum dry density
Inclinometer
A device that measures the inclination from the horizontal of a special casing by measured of a downhole wireline. Slope vs. depth data is recorded.
Often used to monitor landslide or slope movements over time.
Manometer
A liquid column instrument used to determine minor changes in atmospheric pressure (Potentiometric levels)
Used for floor level measurements for monitoring embankment settlement, and measuring liquid levels in tanks.
Magnetometer
Measures strength or orientation of magnetic field.
Used for mineral and oil exploration, as drill guidance systems, locating hazards for tunnel boring machines, in Plate tectonic research, mapping geological structures, detecting geologic hazards in coal mines, or detecting subsurface materials with magnetic characteristics such as toxic waste drums.
Datalogger
An electronic logging device that measures temperature, pressure, humidity, and water levels.
Used to record soil moistures, water levels, water flow, pH, conductivity and monitor deformation.
Piezometer Uses
Monitors natural ground-water levels or to measure and monitor changes in ground-water levels resulting from loading at the surface due to construction or the effect of raising the water level in a reservoir.
Lysimeter Uses
Used to sample water chemistry in the vadose zone, measure deep percolation and evapotranspiration.
Steel Casing
Most commonly used, good structural integrity, stainless steel varieties extend life of the well and offer more protection against corrosion.
Cement casing
Used in deep wells, often for oil and gas wells, different types of cement are used according to specifications, often fails if not placed correctly
Plastic (ABS, PVC)
Best in shallow wells up to 8’ diameter, not as good for deep wells because of cost and limited strength.
Fiberglass casing
Used in corrosive water, shallow to medium depth wells, costly.
Conductor Casing
The casing that is the largest, drilled and set first to prevent the sides of the hole from caving.
Wire Wrap or continuous slot
Developed for use in non-gravel pack wells in glacial deposits. The shape of the openings reduces clogging and a smaller aperture is possible to achieve 90% retention. The large surface area of openings has a greater intake area, exposing it to corrosion and incrustations, leading to lower collapse strength. It is more difficult to develop with mechanical methods.
Bridge Slot
Vertical slots arranged in a staggereed pattern give a high surface area of openings. It has a low production cost, and a lower strength because many openings may lead to collapse.
Shutter Screen
Originally designed for gravel pack wells. Felxibility for different surface openings and patterns make it more customizable. It has a high collapse strength. Development is easier.
Entrancce Velocity
Frictional head losses as the water enter the well screens should be minimized. Proper selection of screen size accomplishes this by maintaining entrance velocities between 1 to 5 feet per second.
Screen length in Homogeneous Unconfined, less than 150 feet thick aquifer
Screen bottom 1/3 to 1/2 of aquifer.
Screen length in nonhomogeneous Unconfined aquifer
Screen the most permeable part of the lower aquifer at up to 1/3 aquifer thickness
Screen length in confined aquifer
Screen 80-90% of aquifer length
Filter pack goal
to optimize well yield of the well but allow only 10% of the fines to enter the well
How do you determine wether or not to use filter pack
Grain size distribution, fine grained materials need filter pack. Filter pack also acts to stabilize the annulus.
Procedure for determining filter pack
- Run grain size analysis and select the grading of the sample on the basis of the finest material.
- Plot the grain size analysis percent passing curve on semi-log paper.
- Plot another curve multiplying the formation size by four times and another curve of 1/6 the formation size, representing the uniformity coefficient d60/d10.
- The filter pack gradation will fall between the curves plotted in step 3.
Multipliers up to 10 may sometimes by used if the material is coarser and nonuniform.
Select a filter material composed of clean, well-rounded siliceous grains of uniform gradation. Calcareous compositions are not desirable. - Select a screen slot size that will retain 90% or more of the filter pack.
Setting the pump
30% safety factor = industry guideline, equivalent to 70% of available drawdown.
Specific Capactiy
is a measure of the pumping rate in gpm divided by drawdown in feet of the well after a 24-hour test.
= Pumping Rate (Q) / drawdown
What is one of the most important indicators of corrosive or incrusting groundwater?
The pH
Corrosion occurs when the following conditions exist:
pH ,< 7
TDS > 1000 mg/L
Dissolved oxygen >2 mg/L
CO2 > 50 mg/L - reacts with rainwater, forms carbonic acid, lower pH
H2S < 1 mg/L - changes electric potential, pits steel
Chloride > 500 mg/L
Incrustation occurs under the following conditions:
pH > 7.5
Iron Precipitation > 0.5 mg/L
Lowered solubility of CaCO3 which forms as incrustations and scale.
Manganese precipitation if oxygen present, >0.2 mg/L.
Baylis Curve
Shows relatively small range of values of pH and alkalinity that allows for quality drinking water. Scale forming vs. Corrosive
Iron bacteria are present in groundwater when
enough iron and/or manganese, dissolved organic material, bicarbonate, or carbon dioxide co-exist. Iron bacteria may also be introduced from the subsoil or during well construction. A pH less than 3 keeps dissolved iron in solution an thus will act as the source of iron for bacterial growth.
How to remediate iron bacteria?
either oxidizers or acids are commonly used, Shock chlorination, consisting of adding amounts of chlorine greater than 1000 mg/L, followed by well agitation, breaks up the masses. Acid treatment may include hydrochloric acid, sulfuric acid or hydroacetic acid.
Wellhead Protection Program
The The 1986 amendments to the Safe Drinking Water Act require states to have a (WHPP) approved by the EPA.
Source Water Assessment Programs
SWAP - in 1996 amendments to the Safe Drinking Water Act required states to develop and implement SWAP to analyze existing and potential threats to the quality of the public drinking water.
Three major steps are outlined to create a source water assessment:
1. Delineate the source water assessment area
2. Inventory for the potential sources of contamination
3. Determine the susceptibility of the water supply to contamination.
Well Development
After construction removal of drill cuttings and drilling fluids that may accumulate in the well and mud cake that developed on well screens. Removal is necessary to increase the well production during development and improve the success of disinfection. Methods of well development may be either mechanical or chemical and include over pumping, backwashing, surging/agitation, air lift, jetting, or acid wash.
Drilling Water and Disinfection
Drilling water must come from an approved potable water supply having a free chlorine residual of at least 10 ppm.
Simplest and most effective way to disinfect water supply system
A chlorine solution between 50-200 mg/L. More chlorine is needed at higher pH water and less at lower pH because chlorine is corrosive at low pH.
Most common sources of chlorine used to disinfect wells
Sodium hypochlorite - common household bleach (5.25 to 6.0%)
Calcium hypochlorite - swimming pool chlorine (10 to 12%)
What standard must chemicals used for treating drinking water meet?
ANSI/NSF/CAN Standard 60 and does not have additives such as algicide. This also applies to corrosion and scale inhibitors; coagulants and flocculants; disinfection and oxidation chemicals; pH adjustment, softening, precipitation, and sequestering chemicals; well drilling aids; and specialty chemicals used in drinking water treatment.
ANSI
American National Standards Institute
NSF
National Sanitation Foundation, Inc.
Seals
Seal the annulus to protect against poor groundwater quality and surface contaminants to a minimum of 50 feet from the surface.
Well Destruction Safety Standards
No national standards, states have their own requirements. Important to prevent contaminants form entering groundwater through the confining layers
Two most typical methods for destroying a well
drilling out the casing and backfilling with an approved sealant or pressure grouting in place. Everything is removed and usually pumped neat cement (grout, no debris) is used to backfill. Backfill can be neat cement grout, 10-sack sand cement grout or a bentonite slurry.
Why are aquifer test performed?
To determine the hydraulic properties and boundary conditions of aquifers.
Drawdown in a pump test
first very rapid, but as pumping continues the rate of drawdown decreases.
bailer or Bail-down test
The well is bailed at a constant rate recording both the rate of wter removal and the drawdown. Used to determine hydraulic conductivity, transmissivity, and specific capcaity.
Pump-in Test
Water is added to the well to maintain a constant water level. This test is usually done in shallow boreholes with access to a water supply. Used to determine horizontal hydruaulic conductivity.
Step-Drawdown Test
A test in which the well is pumped at a series of increasingly higher pumping rates with measurements of drawdown at each change. USed to obtain hydraulic conductivity, transmissivity, storage coefficient and shows reduction of specific capcaity with incrased yields. Allows the computation of turbulent and laminar drawdown needed to determine the optimum pumping rate and pump depth. Used as a well-performacne test.
Constant-Rate Pumping Test
A well is pumped at a constant rate for a given period of time (usually 24 or 72 hours) and drawdown is measured periodically utilizing one oro more observation well for recording data. Usually recovery is also recorded. Used to determine the specific capcaity of the well, transmissivity and storage of the aquifer.
Theis Method
The mathematical model most often used for analysis of aquifer tests. This model is an exact analytical solution for hte radial flow of groundwater in a confined aquifer to a well.
Theis Method Assumptions
- Transmissivity of the aquifer tapped by the pumping well is constant
- The water withdrawn from the aquifer is derived entirely from storage and is discharged instantaneously with the decline in head.
- The discharging well penetrates the entire thickness of the aquifer and its diameter is small in comparison with the pumping rate, so that storage in the well is negligible.
- Materials are homogenous and isotropic.
SWAP
Source Water Assessments Programs
WHPP
Wellhead Protection Program
Theis Drawdown Equation
T = 15.3 Q W(u) / s
Q = pumping rate (gal/min)
s = drawdown (feet)
t = time (minutes)
r = distance from pumping well to observation well (feet)
W(u) = well function of u ( an infinite series)
Formula for u
= 360 r^2S / Tt
How is drawdown plotted for more than one observation well
on log-log paper versus t/r^2
Time-drawdown method
Also known as Jacob straight-line method, a simplified approach to the solution of the Theis equation.
-Drawdown from one pumping well is noted in an observation well, and drawdown values are plotted on semi-log paper as a function of time since pumping started.
-A straight line is drawn through the data points and extended backward to the zero-drawdown axis.
-The straight line is fit through the points farthest from the pumping well because these points are more accurate.
-Aquifer parameters are then calculated using the slop of the straight line and the intercept of the line with the time axis when drawdown is zero.
Data during the first ____ minutes of a pump test are relatively invalid.
10 minutes
Time-drawdown (Jacob-straight line) method equations for Transmissivity and storativity.
T = 35Q / ds
S = T to / 640 r^2
Units of measurement for Theis and Jacob straight-line method
ft^2/day
Distance-drawdown method
-A variation of the Jacob method if the drawdowns in three or more observation wells are measured simultaneously.
-In this situation the drawdown varies with the distance from the pumping well in accordance with the Theis equation
-Drawdown are plotted on the arithmetic scale as the time-drawdown method and distance is plotted on the log scale (x-axis).
-The data will form a straight line first through the points closest to the pumping well.
T Calculation for Time-drawdown
ft^2/day = 35Q / ds
gpd/ft = 264Q / ds
T Calculation for Distance-drawdown
ft^2 / day = 70Q / ds
gpd/ft = 528Q / ds
Conversion from 1 gpd/ft to ft^2/day
= 0.134 ft^2/day
Conversion from 1 ft/day to gpd/ft^2
= 7.48 gpd/ft^2
How to estimate well efficiency from the distance-drawdown graph
Assumption - full thickness of the confined aquifer is screened.
- Plot the points and fit a straight line through them. Extend the line back toward the pumping well.
- Plot the radius of the pumped well.
- The intersection of the straight line with the radius of the pumped well is the theoretical drawdown for a well that is 100% efficient.
- Compare the theoretical value of drawdown from the plot with the actual drawdown measured in the well, which is more than the theoretical drawdown.
- Find the ratio between the theoretical and actual drawdown. This is the well efficiency.
What is the maximum well efficiency in ideal conditions
80% while a value of 60% is more realistic.
Where are national guidelines for drilling and installing groundwater monitoring wells and groundwater sampling described?
In EPA document “Handbook of Suggested Practices for the Design and Installation of Ground-Water Monitoring Wells”
What is the National Ground Water Association well construction standard?
ANSI/NGWA A-01-14, however each state and local jurisdictions adopt individually.
Ideal monitor wells and placement
a minimum of 3 downgradient and 1 upgradient
Standard monitor well construction
Small diameter, usually 2 or 4 inch, to be able to accommodate the transducers and to be able to effectively sample.
What is ideal monitor well construction material?
Non-reactive well screens and casings (stainless steel, PVC, or Teflon) depend on the contaminants present.
Monitor well sterilization
All materials must be sterilized prior to placement in well.
Monitor well drilling technique?
Must be drilled using a method that precludes the introduction of foreign materials into the formation fluids - this usually means no drilling fluids.
Monitor well seal placement?
Seals must be placed to preclude potential for contaminating other units - this usually means sealing the entire annular space.
Where are national guidelines for groundwater sampling described?
In the EPA “Handbook of Suggested Practices for the Design and Installation of Ground-Water Monitoring Wells” and “Ground-Water Sampling Guidelines for Superfund and RCRA Project Managers”
Groundwater sampling method depends on what factors?
-type of device used
-sampler intake position (either within the screen or above the screen)
-purging method used
-condition of the groundwater
Why is purging important and what device should be used?
To insure that the water tested is representative of the in-place water. The same device sued for purging should also be used for sampling and should not change the physical or chemical properties of the groundwater or increase turbidity.
Purging devices should be constructed of Teflon, stainless steel, or glass. Ideally, positive-displacement pumps or low-flow submersible pumps are recommended to prevent overpumping the well.
Purging method: purge 3 to 5 well casing volume minimum
Requires removal of a minimum of 3 well bore volumes to remove the stagnant water in the blank casing in conjunction with testing for water quality stabilization. Sampling would occur after either a minimum of 3 volumes or testing indicates stabilization.
Limitations: Pure 3 to 5 well casing volume
Initially based simple on volumes of water but testing technology allows verification of stabilization for the least pumping volumes. Can’t be used in low-flow wells, turbid water, or fractured rock.
Purging to stabilization (well volume approach)
Requires removal of the stagnant water in the blank casing in conjunction with continuous monitoring of pre-established groundwater indicator parameters until the variation is acceptable.
Limitations: Purging to stabilization (well volume approach)
Criteria for indicator parameter stabilization must be established prior to testing.
1. Time interval of measurements
2. minimal purge time
3. purge rate
4. parameter selection
Low-flow Purging (Minimal Drawdown Methods)
Requires water be pumped from the screened interval until continuous monitoring of pre-established groundwater indicator parameters shows an acceptable variation. This method presumes isolation of the water in the screened interval from the stagnant water in the blank casing.
Limitations: Low-flow Purging (Minimal Drawdown Methods)
Well screen must be less than 10 feet. Careful measurement of pumping rate and water levels required. Well drawdown must be minimized.
Standard equipment for purging and sampling monitoring wells
pumps: suction, peristaltic, positive displacement, submersible
bailers
in-situ devices
Preferred equipment depends on a number of well conditions such as well diameter, depth to water, water volume in the well, accessibility of the well site and the type of contaminants being monitored.
One of the biggest problems when sampling groundwater
VOCs since differing amounts of turbulence will result in different levels of VOC release from the water.
Grab Samplers (Bailers)
Collects water through a bailer type device. Bailers have a check valve at the base of the device. This valve is blocked by a check ball that allows water in using the pressure differential between the inside of the bailer and the outside, then the check ball seats as the bailer is withdrawn retaining water sample. Double check valves are generally required for sampling in water monitoring wells.
Conventional bailer, Dual-check valve bailer, Syringe pump (Grab Sampler - Bailer)
Advantages and Disadvantages
Inexpensive, easy to use and easy to clean. No outside power source is required
Can detrimentally impact the well possibly causing issues with sample quality. Time consuming and labor intensive. Transfer to sample jars can cause aeration which impacts VOC levels. Requires complete removal of stagnant water in blank casing.
Bat Sampler, Hydropunch, Geoprobe (Grab Sampler - Bailer)
Advantages and Disadvantages
Well development not required as sample is retrieved from depth the device is pushed to.
Requires heavy equipment to push the samplers into the ground.
Positive-displacement Pumps (Submersible)
There are a variety of this type of pump that might be appropriate for use in monitoring wells. The principle behind this type of pump is the fluid is moved by trapping a fixed amount of it then forcing the trapped fluid into the discharge pipe. They are constant flow pumps where the flow is the same for any given speed regardless of pressure. This is the preferred method of water removal for sampling water monitoring wells. Low flows are optimal for water sample collection because the agitation of the water can cause higher than normal turbidity and allow the release of VOCs.
Bladder Pump (Positive-displacement Pump)
Advantages and Disadvantages
Nearly continuous flows can result from a properly operating pump. Practical to a depth of about 100 feet. Optimal for VOC sample collection.
Difficult to decontaminate so dedication to one well is recommended. Requires a power supply and a compressed gas/air supply.
Helical Rotor (Positive-displacement Pump)
Advantages and Disadvantages
Can be used for both sallow and deep wells. Good for purging prior to sampling.
Requires a power supply. May cause agitation of sample making it not as appropriate for VOC sampling Difficult to decontaminate.
Stabilization Criteria for Water Quality Indicators (In order of stabilization)
pH - +/- 0.1
Temperature - N/A
Specific Conductance - +/- 3%
Oxidation-Reduction (Redox) Potential - +/- 10 millivolts
Dissolved Oxygen - +/- 0.3 milligrams per liter
Turbidity - +/- 10% (if turbidity > 10NTUs)
Adsorption
The attraction and adhesion of ions or molecules in solution onto the surface of a solid.
Advection
The process by which solutes are transported by flowing groundwater
Diffusion
The process of movement of solutes from areas of higher concentrations to areas of lower concentrations.
Dispersion
The spreading and mixing of a solute in groundwater because water containing the solute is traveling at a different velocity than the groundwater. The result is a dilution of the solute at the advancing edge of the flow.
Effluent
Liquid waste discharged to the environment from a treatment or manufacturing facility. It could be untreated, partially treated or completely treated.
Equivalent weight
The formular atomic weight of a dissolved ionic species divided by the electrical charge.
Hardness
A property of water in which evaporation produces a scale and in combination with soap produces an insoluble residue. Hardness is caused principally by the presence of calcium and magnesium ions although other ions may also be present like iron or manganese.
Hardpan
A hard, impervious near-surface soil layer, usually in clayey soils, formed by cementation from the precipitation of insoluble materials such as silica, iron oxide, calcium carbonate, and organic matter.
Infiltration
The downward flow of water from the surface into and through soils and porous rock.
Leachate
Water that has percolated through solid waste and has accumulated a high amount of dissolved solids.
Maximum Contaminant Level (MCL)
The maximum level of contaminants permitted in water which enters the distribution system of a public water system. MCLs are enforceable standards and are based on health risks.
Milliequivalent per liter
A measure of the chemical equivalence of the concentration of all solutes present in solution. The units are obtained by dividing the concentration (in mg/L) by the equivalent weight.
Part per billion (ppb)
A measure of the solute concentration in a solution that represents mass of the solute per total mass of the solution x 10-9. One ppb is equivalent to 1 microgram (10-6 gram) of solute per liter (ug/L).
Part per million (ppm)
A measure of the solute concentration in a solution that represents mass of the solute per total mass of the solution x 10-6. One ppm has 1 gram of substance for every million grams of solution. Because the density of water is 1 gram per ml, and there is a very small amount of solute, the density of a solution at this low concentration is approximately 1 gram per ml. Therefore, the density of a 1 ppm solution is approximate to 1 milligram per liter (mg/L).
PicoCuries per liter (pCi/L)
A unit of radioactive decay rate; the quantity of radioactive material producing 2.22 nuclear transformations per minute.
Reference Dose
A scientific estimate of a daily exposure level that is not expected to cause adverse health effects in humans.
Retardation
The reduction of overall solute flow relative to the groundwater due to adsorption.
Secondary Maximum Contaminant Levels
The maximum levels of constituents in water at the point of delivery to the consumer that affect the taste, odor, or appearance of drinking water. Federal standards are nonenforceable.
Sodium Adsorption Ration (SAR)
The ratio of sodium to calcium that indicates how much calcium in the soil has been replaced by sodium.
Sorption
Processes that act to remove solutes from groundwater.
Tracers
Elements or compounds used to determine the flow direction or course of the groundwater. Tracers must be detectible at low concentrations and must not react with the aquifer materials or water.
Total Dissolved Solids (TDS)
The total amount of minerals dissolved in water; the sum of the chemical constituents in mg/L for water that contains more than 1000 mg/L dissolved minerals.
Quality Assurance
is a management process that deals with policy development, establishment and evaluation of processes, how implementation of those processes will be accomplished, and review of data collection and applications.
Procedures are designed to ensure that the quality requirements are met and are applicable to the task at hand.
Quality Control
A technical application function whereby the processes, calibrations, procedures and performance conform to the defined standards applicable to the project and meet the requirements of the customer.
Problems that occur and can be addressed by Quality Control are Instrument drift, Lab contamination, Calibration errors, Dilution errors, Dirty glassware, human error.
Significant Figures
- zeros within a number are significant
- zeros in front of a decimal place are not significant
- zeros after a decimal place are significant
- the accuracy of the final answer can be no greater than the least accurate measurement.
Federal Standards to protect the quality of drinking water.
Developed by the EPA and are known as National Primary Drinking Water Regulations. They cover microorganisms, disinfectants and byproducts, inorganic and organic chemicals and radionuclides.
What are the two main water quality problems for agriculture?
Salinity and Toxicity.
Negative consequence of high dissolved solids in water for agriculture
insoluble precipitates such as calcium carbonate may accumulate and form a a hard, impervious layer called hardpan through which roots cannot penetrate. This blocks the movement of groundwater and therefore additional salt can build up.
How does the degree of salt or salinity impact plants?
Plants have a difficult time removing enough water through their roots, and soil permeability is reduced, so that water cannot infiltrate.
What are toxicity of plants to specific minerals?
Boron, chlorides and sodium can stunt plant growth. Excess sodium is the most common sensitivity of plants. Highly sodic irrigation water can destroy a clay soil structure by dispersing the particles as the sodium is exchanged fro calcium or magnesium existing in the clay. The sodium decreases the soil permability, increases the plasticity and can lead to alkali soils. This is not a problem if enough calcium and magnesium are available for hte exchange. Therefore the ratio of sodium to calcium and magnesium is important in evaluating sodium buildup.
SAR measuremetns
A low SAR (2 to 10) indicates a low hazard from sodium; a high SAR (11 to 26) is rates as a high sodium hazard.
How is SAR measured
= NA / (SqRT (CA + MG / 2))
How is TDS often estimated?
Based upon the specific conductance measured and multiplied by a factor between 0.55 and 0.75 approximates the value.
Also inversely proportional to the resistivity of the formation water.
Classification of Groundwater based on TDS
Fresh 0-1,000
Brackish 1,000 - 10,000
Saline 10,000 - 100,000
Brine > 100,000
U.S. EPA recommends what TDS in their National Secondary Drinking Water Regulations.
500 mg/L TDS
Maximum TDS suitable for livestock
5,000 mg/L although much lower concentrations are recommended. Sheep and cattle can become accustomed to higher amounts of TDS in the level of 10,000 to 12,000 mg/L.
Hardness was initially used to indicate what?
how “hard” it was to make soap produce suds.
Hardness is assessed how?
The convention used to quantitatively express hardness is a concentration that is equivalent to calcium carbonate.
Hardness is computed by multiplying the sum of the milliequivalents per liter of calcium and magnesium by 50.
How does boiling help reduce hardness?
Causes the calcium and magnesium to combine with bicarbonate (HCO3) and Carbonate (CO3) ions and precipitate.
Carbonate Hardness
The part of the total hardness that can be removed. While the part that can’t be removed is noncarbonate hardness.
Noncarbonate Hardness
Results from the combination of calcium and magnesium with chloride, sulfate, and nitrate ions, or the presence of other ions such as iron.
Hardness expressed as CaCO3 Concentrations
Soft - 0-60 mg/L
Moderately hard - 61 - 120 mg/L
Hard - 121-180 mg/L
Very Hard - > 180 mg/L
What is the optimum range of hardness for home uses?
Moderately hard 61 - 120 mg/L
Ideally, hardness of drinking water should be less than 80 mg/l, although no standards have been set by the U.S. EPA.
Effects of Hard and Very Hard Hardness
Hard - Considerable scale will be deposited in boilers and water heaters. Laundry may be stiff and dingy. Ideal for paper and pulp producers.
Very Hard - Substantial scale deposited and staining. Water that is very hard is commonly softened for household uses. In limestone and gypsum terranes, water hardness is very high. Values of over 200 mg/L are common and may be as high as 1,000 mg/L.
What 8 ions are over 90% of the dissolved solids in groundwater attributed to?
Na, Ca, K, Mg, Cl, HCO3, SO4, and CO3.
What does a complete water quality analysis verify.
That the sum of the weight of the cations is equal to the sum of the weight of the anions in the solution. If the analysis has identified all the major cations and anions in the water, the sums should be equal. A standard analysis does not report values of TDS, but the concentrations of cations and anions, when added together will give the TDS.
Groundwater Cations
Na, K, Ca, Mg, Fe
Groundwater Anions
Cl, HCO3, SO4, CO3
Milliequivalents per liter (meq/l)
are a way to express the chemical equivalence of the unit concentrations of all ions. In other words, the ion species are balanced for their atomic weight and valence.
Equivalent weight
The ratio of atomic weight to valence. Equivalent weights cannot be calculated for compounds with no electrical charge ( for example, silica)
Stiff Cation and Anion arrangement
Cations are on the left ( Na + K, Ca, Mg, Fe)
Anions are on the right ( Cl, HCO3, SO4, CO3)
Naturally occuring pollutants include…
weathering, erosion, and accumulation of chemical constituents found naturally occurring in rock or soil formations; and contaminants that may cause severe health and genetic problems such as selenium, or radioactive materials such as radon. Salt water intrusion can also render water unusable.
Arsenic
naturally occurring metalloid used as an alloy or its compounds used as pesticides, herbicides, and insecticides. The Drinking water standard for arsenic adopted by the U.S. EPA is 10 ppb (or 0.01 mg/L)
Lead
Naturally occurring metal commonly found in the environment from human activities such as burning fossil fuels , mining and manufacturing. Exposure can be by breathing dust, eating contaminated food, or drinking from lead pipes. Houses before 1978 may also have lead-based paint.
Lead exposure may result in behavioral problems, learning disabilities, seizures, damage to the kidneys, nervous system and reproductive system, and death.
Mercury
Enters the air from mining ore deposits, burning coal or manufacturing. It enters the water or soil from naturally occurring deposits waste disposal or volcanism. Mercury may be concentrated in fish or shellfish and may be related in the body as a results of dental work.
Mercury exposure can lead to permanent brain and kidney damage, and can damage developing fetuses.
Cadmium
Used in the production of batteries, for metal soldering, and welding. Breathing contaminated air from the workspace or cigarette smoke is the most common way to be exposed to cadmium.
Cadmium will damage the lungs, kidneys, and digestive tract.
Chromium
has several forms, one of which (Chromium III) is an essential nutrient for the body and another (Chromium VI) which is carcinogenic.
At high levels Chromium VI can cause lung cancer. OSHA has adopted several standards for exposure to Chromium VI to reduce the health risk.
White Phosphorus
Manufactured from phosphate rocks for chemical manufacturing and smoke munitions. Exposure results from breathing contaminated air, eaeting contaminated fish or game, or touching soil or water contaminated with white phosphorus.
It is not classified as a carcinogen by the U.S. EPA, but it can cause liver heart or kidney damage and irritation of the throat and lungs.
Selenium
Naturally occurring element found in the black marine shales in the western U.S. Selenium accumulates in the soil from the weathering of pyrite in the shales.
Nitrate
a form of nitrogen that is found in soil, particularly in agricultural areas. Primary sources of excess nitrate are fertilizers, animal manure, and leaking septic systems. Since high levels of nitrate and chloride indicate contamination from leaking septic tanks or manure, it is also a strong indicator that high bacterial levels may also be present.
Nitrate is soluble in water, is mobile and accumulates in groundwater. Natural concentrations in groundwater range from 0.1 to 10 mg/L. Infants who ingest high-nitrate water are susceptible to a potentially fatal disease called methemoglobinemia (blue-baby syndrome) that causes low oxygen levels in their blood. Adults are not effected. Drinking water standards for nitrate are set at 10 mg/l of nitrogen.
Perchlorate
The perchlorate ion (Clo4) forms salt compounds with potassium, sodium or ammonium. Perchlorate is soluble and mobile in water and poses a problem as a contaminant because it is persistent under normal groundwater conditions and doesn’t react with other available constituents.
Perchlorate disrupts the thyroid by interfering with iodide uptake which affects human metabolism, growth and development. The U.S. EPA determined that perchlorate does not meet the criteria for regulation under the Safe Drinking Water Act.
Ammonium perchlorate
The primary form of perchlorate and is manufactured as a solid propellant for rockets, missiles, and fireworks. Because it has a limited shelf life, it is manufactured in large quantities and frequently replaced and disposed of.
List of top Inorganic Contaminants
Arsenic
Lead
Mercury
Cadmium
Chromium
White Phosphorus
Selenium
Nitrate
Perchlorate
List of Top Disinfection Byproducts
Chloroform
Trihalomethanes (THM)
THM
Trihalomethanes
Chloroform
can be formed when chlorine is added to water. It slowly breaks down into phosgene and hydrogen chloride which are toxic.
Chloroform can damage the liver and kidneys and is considered to be carcinogenic. Chlorine is one of the chemicals making up total trihalomethanes.
other names for chloroform
Trichloromethane or methyl trichloride
Trihalomethanes (THM)
Organic compounds formed either by the disinfection of water by chlorination or found in natural waters containing high concentrations of dissolved organic compounds and bromides.
THM compounds are carcinogenic.
Total trihalomethanes
The sum of the concentrations of chloroform, bromodichloromethane, dibromochloromethane, and bromoform.
Two dangerous biological contaminants
Crytosporidium and Giardia lamblia
Giardia lamblia
is a protozoan that causes giardiasis, an intestinal disease. When it is waterborne in the form of a cyst, it is resistant to treatment by chlorine.
Cryptosporidium
is a chlorine-resistant protozoan that can endanger entire water supply systems, causing death.
List of top dangerous organic contaminants
LNAPL
DNAPL
Trichloroethylene
Vinyl Chloride
Polychlorinated Biphenyls
Polycyclic Aromatic Hydrocarbons (PAH)
BTEX
MTBE
What does LNAPL stand for?
Light non-aqueous phase liquids
LNAPLs
Are less dense with respect to the density of water. derived mainly from petroleum products and additives to petroleum products.
What does DNAPLs stand for?
Dense non-aqueous phase liquids
DNAPLs
Only slightly soluble in water and are more dense with respect to the density of water and are derived mainly from the following classes: creosote, coal tar, PCB oils, and chlorinated solvents.
What does NAPL stand for?
non-aqueous phase liquids
How are NAPLs characterized?
By their density, viscosity, solubility in water, interfacial tension with water, vapor pressure, wettability, and component composition. These characteristics affect their behavior, their location in the groundwater, their fate and transport, and hence their remediation.
In the unsaturated (vadose) zone, what four phases can NAPLs exist?
NAPL (pure product); gaseous; aqueous; or solid (on soil or aquifer material).
In the saturated zone, what three phases can NAPLs exist?
NAPL, aqueous; or solid
Are LNAPLs soluble in water?
Many LNAPLs are sparingly soluble in water but some are highly soluble.
What happens when LNAPLs are spilled on the land surface?
Will migrate mainly vertically through the vadose zone as a result of gravity and capillary forces. LNAPL will accumulate when it reaches the capillary zone. If the quantity of LNAPL is great enough the water table may be depressed by its thickness.
Different types of LNAPL remediation methods
Excavation, trenches or drains, recovery wells, soil-vapor extraction, air sparging, enhanced oil recovery technologies, bioremediation, groundwater pump and treat, or construction of a physical barrier.
What type of contaminant is gasoline?
An organic contaminant, classified as an LNAPL. Can be cleaned up naturally by using microorganisms.
LNAPL Contamination pathways
-Migrates vertically under the force of gravity
-Lateral migration may occur in response to head distribution of LNAPL or presence of low permeability layers.
-Once it reaches the capillary fringe LNAPL move laterally as a free-phase layer due to gravity and capillary forces.
-4 phases (vapor, solid, aqueous, and immiscible) and 6 partition pathways (soil gas-soil, soil gas-water, soil gas-LNAPL, LNAPL-soil, LNAPL-water, and water-soil) possible in vadose zone.
-3 phases (no vapor phase) possible in the saturated zone.
-Processes that determine fate of contaminants: volatilization, dissolution, sorption, biodegradation.
DNAPL migration pathways
-Migrates downward under gravity and soil capillarity and accumulates in the bottom of the aquifer.
-Once it reaches a stratigraphic unit of lower permeability, it will migrate laterally, controlled by the gradient of the stratigraphy and not the direction of groundwater flow.
-4 phases (vapor, solid, aqueous, and immiscible) and 6 partition pathways (air-soil, air-water, air-DNAPL, DNAPL-soil, DNAPL-water, and water-soil) possible in the vadose zone.
-3 phases (no vapor phase) and 3 partition pathways (DNAPL-water, soil-water, soil-DNAPL) possible in saturated zone.
-Fate and transport depends on characteristics of DNAPL and subsurface media.
Different types of DNAPL remediation methods?
Removal by pumping or trench or drain systems, soil-vapor extraction, biodegradation, soil flushing or construction of physical barriers, Monitoring wells for DNAPL should be screened at the bottom of the aquifer just above the underlying confining layer.
LNAPLs contaminants from gasoline?
Methyl tert-butyl ether
Toluene
Ethyl Benzene
Zylenes
Benzene
Solubility of MTBE?
50,000 ppm, high solubility makes it very mobile.
Trichloroethylene (TCE)
An organic contaminant, is a solvent used to clean metal parts (degreasing) and is an ingredient in typewriter correction fluid and spot removers, Skin contact from swimming or showering, or breathing air contaminated with TCE produces nervous system effects, liver and lung damage, coma or death.
Common DNAPLs
Chlorobenzene
Chloroform
Carbon Tetrachloride
-ethane
-ethylene
-ethene
-ethylene
Vinyl Chloride
An organic contaminant, colorless gas, is also known as chloroethene, chloroethylene, and ethylene monochloride. It is formed when other substances such as trichloroethane (TCA), trichloroethylene (TCE), and tetrachloroethylene (PCE or Perc) are broken down. It is used in the production of PVC pipes, cable coating, and packaging materials, Extremely high levels can cause death, while prolonged breathing results in liver damage, immune reactions, nerve damage and liver cancer.
TCA Acronym
Trichloroethane
TCE Acronym
Trichloroethylene
PCE or Perc Acronym
Tetrachloroethylene
Polychlorinated Biphenys
PCBs, organic contaminants, are oily liquid or solid chlorinated compounds that were manufactured and used as coolants and lubricants in electrical transformers and capacitors. They have not been used since 1977 because of mounting evidence that they cause skin, immunological and liver damage and are carcinogenic. Many PCBs were manufactured under the brand name Aroclor.
PAH Acronymn
Polycyclic Aromatic Hydrocarbons
Polycyclic Aromatic Hydrocarbons
PAH, organic contaminant (voc), this category includes Benzo(A)Pyrene, Benzo(b)Fluoranthene, and Dibenozoa(A,H)Anthracene. PAHs are a large group of chemicals formed from incomplete combustion of coal, oil, gas, garbage, or other substances. They may also be manufactured. Breathing PAHs can lead to lung cancer, stomach cancer, or skin cancer.
MTBE Acronym
Methyl Tert-Butyl Ether
Methyl Tert-Butyl Ether
A organic contaminant (vos) gasoline oxygenate added to fuels since early 1990’s. It’s use became widespread because of the requirement by the Federal Clean Air Act Amendments of 1990 that carbon monoxide and ozone levels be reduced. While the use of MTBE in gasoline has improved air quality, it has had a negative impact on groundwater quality.
Why is MTBE so problematic?
is mobile, soluble, resistant to decomposition by microbes, and difficult to remove in water treatment. It accumulates from storm runoff and from leaking underground storage tanks. Reservoirs that permit jet skis with two-stroke engines that incompletely combust the gasoline are another source of MTBE. In drinking water it imparts a solvent-like taste, and even through the U.S. EPA has classified MTBE as a possible carcinogen, there is no drinking water standard.
Problematic characteristics of MTBE
-Density of 0.74 g/mL
-Biodegrades slowly
-Solubility of 50,000 ppm, high solubility makes it very mobile
-Doesn’t easily adsorb onto soil
-Volatilizes quickly in surface waters
-Usage as oxygenate in gasoline replace by ethanol
-Has been banned but was found in the gasoline from 1979 to 2005
DDT, DDE, DDD
Compounds are pesticides that are now banned in the U.S. Exposure comes from eating food contaminated with these substances. DDT can affect the nervous system, cause liver cancer, and disrupt the reproductive system.
Chlordane
A termite pesticide that was used until 1988. It is found in contaminated root crops, meat, fish, or seafood. It breaks down very slowly and bio-accumulates, eventually affecting the nervous system or liver.
Aldrin/Dieldrin
These compounds are insecticides that were banned for all uses in the U.S. in 1987. They are found in contaminated root crops, fish, or seafood and bio-accumulate, eventually affecting the nervous system.
Main consequences of banned pesticide exposure
Nervous system and liver damage.
Brownfields
Defined by the Brownfields Revitalization and Environmental Restoration Act of 2001 as “real property, the expansion, redevelopment, or reuse of which may be complicated by the presence or potential presence of a hazardous substance, pollutant, or contaminant. The purpose of this legislation is to encourage remediation, if needed, so that the site can be redeveloped.
Brownfields redevelopment process
Starts with a Phase I site assessment and the due diligence process. If the phase I site assessment reveals no apparent contamination and no significant health or environmental risks, redevelopment activities may begin. However, if apparent contamination is revealed, then a Phase II site investigation is required.
Phase I, II, III
Phase I - Determine the extent of contamination and possible legal and financial risks.
Phase II - involves sampling the site to determine the type, quantity and extent of the contamination.
Phase III - the cleanup phase.
OWM Acronym
Office of Wastewater Management - EPA
What does the OWM do?
promotes designing and maintaining septic systems that comply with the requirements of the Safe Drinking Water Act and the Clean Water Act. They issues guidance documents that although are unenforceable are useful to understand the technical issues relating to septic systems and leachfields.
Onsite Wastewater Treatment Systems Manual
Issued by the OWM, covers wastewater treatment and septic system design and establishes performance requirements rather than prescriptive codes.
Performance issues to consider for residential leachfields:
-Estimating wastewater characteristics - daily volumes, flow rates, pollutants
-Estimating wastewater flow - daily peak flows
- Minimizing flow and pollutants - hydraulic overload (reduce water use, fix leaks)
- Integrating wastewater characterization (Flow Chart)
-Transport and fate of pollutants in the receiving environment.
Common residential leachfield contaminants that require mitigation.
Pathogens
Organic Compounds
Metals
Surfactants
Phosphorous
Nitrogen
Pathogens in onsite wastewater contamination
Mostly contributed through human waste products. Bacteria is most often removed within three feet by infiltration, sedimentation and adsorption. Karst and high groundwater can introduce pathogens into groundwater. Viruses are not normally part of human waste unless a person is infected. They are retained by adsorption but are less affected by infiltration and may be persistive in soil. Two feet of fine sand may be enough to remove almost all viruses. Protozoa like Giardia and Cryptosporidium are killed when frozen, but Cryptosporidium is much more resistant than Giardia to other killing or inactivation methods like ozone or chlorine dioxide.
Organic Compounds in onsite wastewater contamination.
Often found in household cleaners and solvents and most commonly in wastewater are the following:
1,4-dichlorobenzene
-methylbenzene(toluene)
-dimethylbenzene (xylene)
-1,2-dichloroethane
-1,1,1-trichloroethane
-dimethylketone (acetone)
These have both a liquid and gas phase to mitigate. Degradation by biological means may be the most effective mitigation.
Metals in onsite wastewater contamination
sources include old plumbing, household products, and human waste. Typical metals found are cadmium, lead, zinc, and copper. Whether they can be removed before entering the groundwater depends on complex reactions and interactions.
Surfactants in onsite wastewater contamination
used in laundry detergents and cleaning products to decrease the surface tension and act as an emulsifier. They may decrease adsorption and change the infiltration rates of soils. The most common surfactant used is LAS - linear alkylbenzenesulfonate. Surfactants may be retained inf there is fine-grained soil and high concentration of organic matter.
Phosphorus in onsite wastewater contamination
Commonly supplied by cleaning products such as dishwasher detergents, silver polish of TSP (TriSodiumPhosphate). It is removed by adsorption, ion exchange and precipitation reactions. When phosphorus ent4ers groundwater, the amount depends on the characteristics of the soil, the thickness of the unsaturated zone through which the wastewater percolates, the applied loading rate, and the age of the system. Although soils are usually able to retain the phosphorus, it is a problem in karst and in coarse-grained soils near surface waters where there is little iron, calcium, or aluminum available to adsorb the phosphorus. If it enters surface waters, it may cause algal blooms that when they die, deplete the water of oxygen.
Nitrogen in onsite wastewater contamination.
Nearly all nitrogen comes in the form of ammonia from urine. With enough oxygen, the process of nitrification occurs, which is the conversion of ammonium nitrogen to nitrite and then nitrate through bacterial action. Nitrate is not effectively removed and can enter the groundwater forming percolate plume. The results of performance testing are quite variable, and the costs of systems designed to reduce nitrogen are very high.
The most successful mitigation is biological denitrification, especially when there is carbon or sulfur available With the aid of anoxic bacteria, nitrate is converted to gas. This is most effective in silts and clays or layered fine and coarse-grained soils.
Wastewater contamination remediation
Suspended solids, fecal indicators, metals and surfactants can be effectively removed by the first 2 to 5 feet of soil under unsaturated, aerobic conditions, Phosphorus may be a problem in karst, and nitrate plumes are formed that will need to be mitigated.
Soil Vapor Extraction (SVE)
remediates, fuels, VOCs, PCE and TCE in the vadose zone by removing volatiles. It promotes in situ bioremediation by providing bacteria with increased oxygenation. It works best in permeable and porous soil, particularly when the soil structure and stratification is well characterized. It is less effective when there is soil moisture. Shallow groundwater less than 3 feet is not desirable.
Equivalent Weights cannot be calculated for what two compounds with no electrical charge?
Silica (SiO2) and Boron (B)
Which Anions & Cations have an electrical charge of +-2
Ca, Mg, SO4, CO3, Sr, Fe
Pump and Treat Method
Pumps contaminated water from the aquifer and brings it to the surface to treat using conventional methods of waste water treatment. Particularly effective for dissolved organic and inorganic chemicals.
Limitations of Pump and Treat Method
- NAPLs are often present in both the dissolved phase and the NAPL phase. It may take many years to remove all of the residual NAPL in the dissolved phase.
- Water discharged to the surface requires a NPDES permit.
NPDES
National Pollutant Discharge Elimination System. EPA regulates storm water discharges at industrial and construction sites.
What is an NPDES permit
Clean Water Act prohibits anybody from discharging “pollutants” through a “point source” into a “water of the United States” unless they have an NPDES permit. The permit will contain limits on what you can discharge, monitoring and reporting requirements, and other provisions to ensure that the discharge does not hurt water quality or people’s health.
Source Control
Improperly disposed solid wastes contribute to groundwater contamination when water percolating from the surface leaches through the waste. To control this process, contaminants are either removed or contained.
Containment Source Control
In-place waste can be contained using an impermeable cap to prevent the infiltration of surface waters, or cutoff walls to prevent groundwater movement through the waste. Cutoff walls have been combined with extraction wells on the upgradient side of the wall to remove the contaminated water and injection wells on the downgradient side to re-inject the treated water.
Removal and disposal Source Control
Wastes are removed to a safe landfill or incinerated (if they are organic compounds)
Hydraulic Isolation Source Control
Contaminated water is contained by creating hydraulic gradients using a combination of injection and withdrawal wells.
Soil-Vapor Extraction (SVE)
Volatile organic compounds (VOC) are extracted by creating a vacuum in air vents or wells in the soil that draws the vapors into the wells. Then moisture is removed and vapor are treated when drawn through activated carbon.
Air Sparging
Utilizes a SVE system to remove the VOCs by injecting air into the soil below the water table. By forcing air bubbles into the soil, contaminants in the groundwater are volatilized and VOCs stripped from the soil. The VOCs then migrate upwards to the vadose zone and are collected and removed by a vapor extraction system.
Air Sparging Limitations
-Requires permeable and porous soils
-Good seal required for well casing
-Air is not evenly distributed because it follows the path of least resistance so there will be a rapid high rate of removal followed by a significant drop in effectiveness.
Bioslurping
Incorporates both a vacuum-enhanced dewatering system to remove free product and bioventing. Pumping removes the contaminates (LNAPLs) from the top of the water table and bioventing of the vadose zone forces air through the soil to remove the soil gas by SVE.
Bioslurping limitations
-Has an high initial rate of removal followed by a lower rate due to diffusion by the replacing water
-Is less effective in low permeability materials
Bioremediation
The process by which naturally occurring microbes, usually bacteria but may also be protozoa or fundi, degrade the organic contaminants remaining on the soil particles. Bioremediation can be enhanced by the introduction of oxygen and/or nutrients.
Bioremediation Limitations
Environmental factors such as pH, Eh, temperature, and the presence or absence of available nutrients (N,K,P) influence the rate at which microbes can metabolize organic contaminants.
- Nutrients must be able to reach the contaminants
-Acclimation period of microbes to contamination may be slow.
-Limited effectiveness for halogenated VOCs.
ASBOG
Association of State Boards of Geology
CERCLA
The 1980 U.S. “Comprehensive Environmental Response, Compensation, and Liability Act” which covers abandoned hazardous waste sites; also known as “Superfund”.
CFR
Code of Federal Regulation
Competent Person
According to OSHA, a person capable of identifying existing and predictable hazards which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them.
Excavation
Any man-made cut, cavity, trench, or depression in an earth surface, formed by earth removal.
IBC
International Building Code. New in 2000, it integrates the Uniform Building Code, the Southern Building Code, and the Building Officials and Code Administrators Code.
Lagging
Boards which are joined, side-by-side, lining an excavation.
OSHA
Occupational Safety & Health Administration, an agency within the U.S. Department of Labor. OSHA enforces occupational safety and health standards and regulatiosn.
RCE
Registered Civil Engineer
RCRA
Resources Conservation and Recovery Act, 1976, as amended (40 CFR, subparts 264, 265). U.S. law that regulates existing hazardous waste facilities; groundwater requirements in the corresponding regulations are performance standards.
Scour
The powerful and concentrated digging action of flowing water during a flood, removing mud and silt.
Spiling
Dowels or pins drilled or driven into the Earth around a shaft to provide support.
TEGD
Technical Enforcement Guidance Document, 1986. A technical guidance document for meeting the groundwater monitoring performance standards in the RCRA regulations.
USC
U.S. Code
Who enforces mining laws?
Office of Surface Mining Reclamation and Enforcement (OSMRE)
OSMRE
Office of Surface Mining Reclamation and Enforcement, enforces mining laws.
National Environmental Policy Act of 1969
- Requires federal agencies to integrate environmental values into their decision making processes by considering the environmental impacts of their proposed actions and reasonable alternatives to those actions.
-Requires federal agencies to prepare an Environmental Impact Statement (EIS) and Environmental Assessments (EA)
EIS
Environmental Impact Statement- as required by the NEPA of 1969
EA
Environmental Assessments - as required by the NEPA of 1969
Safe Drinking Water Act of 1974
- The main federal law that ensures the quality of drinking water from surface or underground.
-Requires public water systems to comply with standards it establishes.
-Protects underground sources of drinking water from underground injection of fluids.
-Authorizes three EPA groundwater protection activities:
1. Underground Injection Control (UIC) regulatory program
2. Sole Source Aquifer (SSA) designation program
3. Source Water Assessment and Protection (SWP) program, which includes Wellhead Protection.
Year of the Safe Drinking Water Act
1974
Year of Nationl Environmental Policy Act
1969
SSA
Sole Source Aquifer
SWAP
Source Water Assessment and Protection
UIC
Underground Injection Control
Clean Water Act of 1972
Formerly Federal Water Pollution Control Act 1948
-Established the basic structure for regulating discharges of pollutants into U.S. Waters
-Gave EPA the authority to implement pollution control programs such as setting wastewater standards for industry.
-Continued requirements to set water quality standards for all contaminants in surface waters.
CWA
Clean Water Act of 1972
Year of the Clean Water Act
1972
Water Quality Act (WQA) of 1987
An amendment to the Clean Water Act that requires that the EPA issue National Pollutant Discharge Elimination System (NPDES) permits to regulate point source pollutant discharges to the nation’s waters
WQA
Water Quality Act of 1987
Year of the Water Quality Act
1987
Surface Mining Control and Reclamation Act of 1977 (SMRCA)
-Established to protect the environment from the adverse effects of mining.
-Designed to assure that reclamation of mined areas is undertaken and to avoid mining in areas that cannot be reclaimed.
SMCRA
Surface Mining Control and Reclamation act of 1977
Year of the Surface Mining Control and Reclamation Act
1977
Toxic Substances Control Act of 1976
-Addresses production, importation, use and disposal of PCB, asbestos, radon, and lead-based paint.
-Maintains inventory of over 83,000 chemicals
-Requires reporting, record keeping and testing of chemicals, and restricts certain chemicals.
Year of the Toxic Control Act
1976
Resource Conservation and Recovery Act of 1976
Grants EPA the authority to regulate hazardous waste management facilities that generate, transport, treat, store, or dispose of hazardous waste.
-Manages non-hazardous solid waste.
-Manages a comprehensive underground storage tank program.
RCRA
Resource Conservation and Recovery Act of 1976
Year the Resource Conservation and Recovery act
1976
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) aka Superfund, 1980
-Provided broad Federal authority to respond directly to releases or threatened releases of hazardous substances that may endanger public health or the environment.
-Requires ATSDR and EPA to prepare a list of hazardous materials at National Priorities List (NPL) sites in order of frequency of occurrence, toxicity, and potential for human exposure, and publish the list every 2 years.
-Established prohibitions and requirements concerning closed and abandoned hazardous waste sites.
-Provided for liability of persons responsible for releases of hazardous waste at these sites.
- Established a trust fund to provide for cleanup when no responsible party could be identified.
CERCLA
Comprehensive Environmental Response, Compensation, and Liability Act aka Superfund, 1980
Year the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)
1980
Brownfields Revitalization and Environmental Restoration Act of 2001
-An amendment to CERCLA which defines Brownfields as “real property, the expansion, redevelopment, or reuse of which may be complicated by the presence or potential presence of a hazardous substance, pollutant, or contaminant.”
-Cleanup up and reinviting in these properties takes development pressures off of undeveloped, open land, and both improves and protects the environment.
Year of Brownfields Revitalization and Environmental Restoration Act
2001
Oil Pollution Act (OPA) of 1990
-Strengthened EPA’s prevention and response to catastrophic oil spills.
- Initiated a trust fund to clean up spills when the responsible party can’t or won’t pay.
- Requires all oil storage facilities and vessels to submit plans on correction of large discharges.
- coast Guard deals with oil tankers regulations, EPA deals with above ground storage facilities.
Year of Oil Pollution Act
1990
OPA
Oil Pollution Act
National Primary Drinking Water Regulations
- EPA set standards for over 90 contaminants in drinking water
- Monitors for unregulated drinking water contaminants.
National Secondary Drinking Water Regulations
Non-enforceable standards that pertain to odor and taste of water
Underground Injection Wells Regulations
EPA regulates the construction, operation, permitting and closure of injection well used to place fluids underground for storage or disposal.
What does OSHA 29 CFR Subpart P, Std. No. 1926 pertain to?
Excavations
What does OSH 29 CFR Subpart H std. No. 1910 Pertain to?
Hazardous Materials
- Outlines the types of hazards based on the levels of protection needed
- Describes the protective gear based on the levels of protection (A,B,C,D)
Arsenic (As) Maximum Contaminant Level
0.010 mg/L
Barium (Ba) Maximum Contaminant Level
2.0 mg/L
Cadmium (Cd) Maximum Contaminant Level
0.005 mg/L
Chromium VI (Hexavalent) Maximum Contaminant Level
0.1 mg/L
Fluoride (F) Maximum Contaminant Level
4.0 mg/L
Lead (Pb) Maximum Contaminant Level
0.015 mg/L action Level
Mercury (Hg) Maximum Contaminant Level
0.002 mg/L
Nitrate (as N) Maximum Contaminant Level
10 mg/L
Nitrite (as N) Maximum Contaminant Level
1.0 mg/L
Selenium (Se) Maximum Contaminant Level
0.05 mg/L
Thallium (Ti) Maximum Contaminant Level
0.002 mg/L
Benzene Maximum Contaminant Level
0.005 mg/l
Total Coliform bacteria
Is used as indicator of other potentially harmful bacteria, though it is not considered a health threat in itself.
Turbidity
Used as a water quality indicator because it is often associated with disease-causing viruses, parasites, and bacteria.
Aluminum Secondary Standard
0.05 to 0.2 mg/L
Chloride (Cl) Secondary Standard
250 mg/L
Copper (Cu) Secondary Standard
1.0 mg/L
Fluoride (F) Secondary Standard
2.0 mg/L
Iron (Fe) Secondary Standard
0.3 mg/L
Manganese (Mn) Secondary Standard
0.05 mg/L
Silver (Ag) Secondary Standard
0.10 mg/L
Sulfate (SO4) Secondary Standard
250 mg/L
Zinc (Zn) Secondary Standard
5.0 mg/L
Color Secondary Standard
15 color units
Corrosivity Secondary Standard
Noncorrosive
Foaming Agents Secondary Standard
0.5 mg/L
Odor Secondary Standards
3 threshold odor number
pH Secondary Standard
6.5 - 8.5
Total Dissolved Solids
500 mg/L
How are excavations defined by OSHA?
as any man/made cut, cavity, trench, or depression in the Earth’s surface made by removing material. Excavations include shafts, bell-bottom pier holes, trenches, benches, and cut slopes.
Access and egress excavation requirements
ramps that are used as a way of entering or leaving the excavation must be designed by a competent person. A stairway, ladder, ramp, or other means of egress must be provided in trenches that are 4 feet or more in depth so as to require that personnel travel no more than 25 feet laterally
Hazardous Atmospheres OSHA Excavation requirements
Adequate precautions including providing ventilation or respiratory protection need to be taken in excavations deeper than 4 feet where the oxygen levels drop below 19.5% or where there is a possibility of the presence of hazardous atmospheric contaminants. If these hazardous contaminants are present, emergency rescue equipment (breathing apparatus, harness, and stretcher) needs to be on site.
Protection from hazards associated with water accumulation excavation requirement
Excavations in which there is accumulated water, or in which water is accumulating, shall not be entered by employees unless adequate precautions have been taken to protect them from the hazard. Such precautions might include special support or shield systems to protect from cave-ins, water removal, use of a safety harness or lifeline, and/or diversion of surface water.
Stability of adjacent structures excavation requirement
If an excavation is below the base of any foundation or retaining wall, a registered professional engineer must determine that the excavation work does not pose a hazard to employees or it must be in stabile rock, or a support system such as underpinning is in place.
Protection from loose rock or soil excavation requirement
Employees must be adequately protected from loose rock or soil that may fall or roll from an excavation face. Such protective measures shall include scaling of the excavation face to remove loose materials, installation of barricades to stop and contain falling material, and other means of equivalent protection. Employees must also be protected from excavated materials that could roll or fall into the excavation. Materials and equipment must be at least two feet from the edge of the excavations, held by retaining devices or both.
Inspections excavation requirements
Daily inspections of excavations, adjacent areas, and protective systems shall be made by a competent person to identify potentially hazardous conditions. Inspections shall be made at the commencement of work and throughout the shift. If hazardous conditions such as rainstorms or earthquakes, the development of cracks fissures, sloughing, seepage, bulging or movement of adjacent structures are observed, employees must leave the excavation until the hazard is mitigated.
Fall protection excavation requirement
Walkways over excavation shall be provided when personnel are required to cross the excavation. Adequate barriers or covers shall be provided for all excavations, pits, shafts, and wells. Guard rails are required where the excavation is greater than 6 feet deep. Upon completion of exploration, excavations shall be backfilled.
Cave-in protective systems requirements?
Protective systems are not required when excavations are made entirely in stable rock or when excavations are less than 5 feet deep and are examined by a competent person who indicates that no potential cave-in conditions exist. Protective systems must be capable of resisting without failure all loads which are intended or could be expected to be applied to them.
Designing slopes and benches using allowable configurations and slopes regardless of soil type
Excavated slopes shall not be steeper than 1.5H:IV (34 degree measured from the horizonal) not be deeper than 20 feet. If the lower portion of the slope is vertically sided, the vertical portion shall be shielded or supported to at least 18 inches above the top of the vertical side.
Designing slopes and benches with classification of soil and rock deposits as set forth in Appendix A of 29 CFR 1926 Subpart P:
Each soil and rock deposit shall be classified by a competent person as Stable Rock, or Type A, Type B, or Type C soil. At least one visual and manual test must be performed to make the analysis.
Designing slopes using tabulated data for design
Requires a professional engineer to evaluate and approve the data on which the slope and benching design was based.
Design of support systems, shield systems and other protective systems
-Use predetermined tables
-Use manufacturers tabulate data
- Use other tabulated data
- Use a design by a registered professional engineer.
Stable Rock: Maximum allowable slope for excavation less than 20 feet deep
Maximum slope - Vertical
Maximum Angle from Horizontal - 90 degrees
Type A: Maximum allowable slope for excavation less than 20 feet deep
Maximum slope - 3/4:1
Maximum Angle from Horizontal - 53 degrees
Type B: Maximum allowable slope for excavation less than 20 feet deep
Maximum slope - 1:1
Maximum Angle from Horizontal - 45 degrees
Type C: Maximum allowable slope for excavation less than 20 feet deep
Maximum slope - 1 1/2 :1
Maximum Angle from Horizontal - 34 degrees
Type A Soil Types
Clay, silty clay, sandy clay. Also caliche and hardpan.
Type B Soil Types
Dry rock that is not stable, angular gravel, silt, silt loam, sandy loam.
Type C Soil Types
Gravel, sand, loamy sand, submerged soil, submerged rock that is not stable.
Installation of supports OSHA Standard
Installation of the support system shall be installed to protect against sliding, falling or other predictable failures. Material can be excavated no more than two feet below the bottom of the support members only if the system is designed to withstand the forces for the entire depth of the trench and there is no loss of soil underneath the support system.
Removal of Supports OSHA Standard
Before removal begins, other structural members shall be installed to carry the loads. Removal of support members shall progress slowly from the bottom of the excavation and backfilling shall alternate with the removal of the supports.
Methods for Safeguarding Personnel Inspecting Shafts OSHA
any shaft or well that a person enters must be cased its entire length. Prior to entry of personnel, all shafts over 5 feet in depth must be retained with lagging, spiling, or casing. The lagging, spiling, or casing must extend at least one foot above ground level and shall continue along the full length of the shaft or at least five feet into solid rock if possible.
OSHA protective levels
Levels A,B,C,D - A is the most restrictive while D is the least. A requires full hazmat and Self-Contained Breathing Apparatus
SCBA
Self-Contained Breathing Apparatus
Level A Protection as specified by OSHA when:
1) The hazardous substance has been identified and requires the highest level of protection for skin, eyes, and the respiratory system based on either the measured high concentration of atmospheric vapors, gases, or particulates; or the site operations and work functions involve a high potential for splash or exposure that is harmful to the skin.
2) Substances with a high degree of hazard to the skin are known or suspected to be present, and skin contact is possible
3) Operations must be conducted in confined, poorly ventilated areas, and the absence of conditions requiring level A have not yet been determined.
Level B protection should be used when:
1) The type and atmospheric concentration of substances have been identified and require a high level of respiratory protection, but less skin protection
2) The atmosphere contains less than 19.5 percent oxygen
3) The presence of incompletely identified vapors or gases is indicated by a direct-reading organic vapor detection instrument, but vapors and gases are not suspected of containing high levels of chemicals harmful to skin or capable of being absorbed through the skin.
Level C protection should be used when:
1) The atmospheric contaminants, liquid splashes, or other direct contact will not adversely affect or be absorbed through any exposed skin.
2) The types of air contaminants have been identified, concentrations measured, and an air-purifying respirator is available that can remove the contaminants.
3) All criteria for the use of air-purifying respirators are met.
IDLH
Immediately Dangerous to Life or Health
Level D protection should be used when:
1) The atmosphere contains no known hazard
2) Work functions preclude plashes, immersion, or the potential for unexpected inhalation of or contact with hazardous levels of any chemicals.
RCRA
Resources, Conservation, and Recovery Act of 1976
What are the essential components of a groundwater monitoring system that meets the water quality objectives of the RCRA?
-Site Characterization
-Placement of Detection Monitoring Wells
-Monitoring Well Design and Construction
-Sampling and Analysis
-Statistical Analysis of Detection Monitoring Data
-Assessment Monitoring
TEGD Guidelines for Site Characterization
- Considered Essential. Goal is to identify potential pathways for contaminant migration ion the uppermost aquifer
- Must define the subsurface site geology and hydrology (flow paths and rates) to support monitoring system design and any cleanup actions needed.
- Minimum investigations includes: geologic data review and mapping, soil borings, material testing and analysis, piezometer studies, slug test and/or pump test. Geophysical surveys are also useful.
Uppermost Aquifer
considered to include all of the hydraulically interconnected units that could be pathways for contaminant migration.
TEGD Guidelines for Placement of Monitor Wells
- Based on the results from Site Characterization
- One upgradient well, 3 downgradient at a minimum. Downgradient wells should be placed to intercept flows.
- Well clusters, screened at different stratigraphic horizons, may be necessary to sample all significant flow zones.
- Horizontal spacing between wells depends on site-specific factors such as hydrogeology, dispersivity, seepage velocity, facility design and waste characteristics.
- Vertical sampling intervals are determined by stratigraphic horizon through which flow will occur, physical/chemical characteristics of hazardous waste, and chemical processes of dispersion and sorption.
TEGD Guidelines for Monitor Well Design and Construction
- Use least contaminating, least damaging drilling methods first, (Auger, hollow-stem, continuous, cable too, air rotary)
- 4-inch well diameter is typical.
- Log all wells
4.Wells should be designed to have a lifetime of 30 years or more. - Do sieve analyses of granular formation material to design filter pack and screen slot size.
- Use chemically inert, well-rounded and dimensionally stable filter pack placed 2 feet or less above the screen and constructed on site.
- Length of well screen is determined by complexity of hydrogeology. The greater the stratigraphic diversity the shorter the well-screen interval.
8.An appropriate annular sealant is a minimum of 2 feet of sodium bentonite pellets placed above the filter pack when in the saturated zone, cement/bentonite mixture in unsaturated zone below frost zone, and continuous pour concrete cap and well apron from below frost zone to surface. - Locking well cap with vent hole for gas.
- Surveyor’s pin on concrete apron.
- Develop wells with surge blocks until sediment-free (wells with more than 5 NTU are unacceptable)
- Document all phases of well design and construction.
Why is mud rotary the choice of last resort when designing a monitor well?
Bentonite, barium sulfate, biodegradable, or organic polymer muds degrade water quality and should not be used.
NTU
Nephelometric Turbidity Units
Surveyor’s pin details
Elevations of top of monitoring well casing, top of steel casing and ground surface elevation must be known within 0.01 foot.
Sampling and Analysis TEGD Guidelines
- Prepare a written Sampling and Analysis (S&A) plan and follow it.
- Water Sample Collection
- Sample Preservation
- Chain of custody
- Analytical procedures
- QA/QC
S&A
Sampling and Analysis Plan
Water Sample Collection TEGD Guidelines
- Measure static water level to 0.01 foot first.
- Determine presence or absence of immiscible contaminants on top of water
- Evacuate well three times, or at least once if slow to recharge.
- Sample with Teflon or stainless steel gas-operated bladder pump, double-check valve bottom bailer, syringe bailer or single-check valve bailer
- Measure pH, temperature, and specific conductance before and after sample collection.
Sample Preservation TEGD Guidelines
- Follow sample preservation, handling, and analytical methods in U.S. EPA SW-846, “Test Methods for Evaluation Solid Waste - Physical Chemical Methods”
- Minimize volatile loss - no agitation, headspace, or pouring from container to container.
- When filtering is necessary, analyze and compare both filtered and unfiltered samples
Chain-of-custody TEGD Guidelines
Labels, seals, field logbook, chain-of-custody record, sample analysis request sheets, and lab logbook.
Analytical Procedures TEGD Guidelines
- Specify analytical method to be used for each constituent, extraction date and date of analysis.
- Performance specifications (deviation of detection limit, sensitivity, precision, accuracy) of reference method should be noted.
QA/QC TEGD Guidelines
- Include trip and equipment sample blanks, standards, lab blanks, duplicates, and spiked samples.
- Follow guidelines for “Evaluation of Quality of Ground-Water Chemical Constituent Data”
- Specify actual detection limit; highlight any values exceeding drinking water standards.
Statistical Analysis of Detection Monitoring Data TEGD Guidelines
- With more complete data bases and permitting programs, use Cochran’s Approximation to the Behrens-Fisher (CABF) t-test.
- With less complete data bases use another t-test such as the Averaged Replicate (AR) t-test.
- Determine mean and variance for each background well and again after the first year. Compare downgradient wells to background wells, compare upgradient wells to background wells, and report an investigate significant differences.
Assessment Monitoring TEGD Guidelines
- Assessment monitoring information is used to evaluate the need to corrective action at the facility or to form the basis for an enforcement order compelling corrective action.
- Quantify the rate of movement and determine the concentrations of Appendix VIII parameters.
- Map the vertical and horizontal extent of the contaminant plume when a leak is detected.
Water Sample Collection TEGD Guidelines
- Measure static water level to 0.01 foot first.
- Determine presence or absence of immiscible contaminants on top of water
- Evacuate well three times, or at least once if slow to recharge.
- Sample with Teflon or stainless steel gas-operated bladder pump, double-check valve bottom bailer, syringe bailer or single-check valve bailer
- Measure pH, temperature, and specific conductance before and after sample collection.
100-Year Flood
A flood that has a 1% probability of occurring in a year.
Active Fault or Holocene Fault
A fault that has exhibited surface displacement within Holocene time (about 11,000 years)
Afterslip
A seismic fault slip that occurs following a large earthquake.
Asthenosphere
Under the lithosphere, it is the weak upper mantle where isostatic adjustments are made, magma generated and seismic waves strongly attenuated.
Attenuation
A reduction in the amplitude of seismic waves produced by divergence, scattering, reflection and absorption.
Avalanche
A large mass of snow, ice, soil, rock, or mixtures of these materials, falling, sliding, or flowing very rapidly due to gravity.
Blind Thrust
A thrust fault that does not reach the surface.
Blind Zone
The area in which there is no possibility for earthquake early warning notifications because it is too close to the epicenter.
Body-Wave Magnitude
Magnitude of an earthquake as estimated from the amplitude of body waves.
Differential Settlement
The uneven lowering of different parts of an engineered structure, often resulting in damage to the structure.
Dilatancy
The increase in volume of rocks due to elastic and nonelastic changes during deformation.
Elastic Rebound Theory
A theory proposed by Reid to explain the cause of earthquakes.
Epicenter
The point on the Earth’s surface directly above the focus.
Factor of Safety
A measure of the stability of a slope in which the resisting forces are compared to the driving forces. If the resisting force is equal to or less than the driving force the slope will fail. Defined as the ratio of the resisting forces (shear strength) to the driving forces.
If the factor of safety is less than 1 the slope will fail.
= resisting forces / driving forces
Fall
A very rapid downward movement of rock or earth that travels most of the distance through the air, either by free fall, leaps and bounds, or rolling.
Fault Creep
Slow ground displacement usually occurring without accompanying earthquakes. It may be of tectonic origin or result form oil or ground-water withdrawal.
Flow
Movement within the displaced mass of rock or soil that continually deforms it. Slip surfaces are not generally visible.
Focus (Hypocenter)
The place where earthquake rupture originates.
Ground Lurching
The movement of an unsupported cliff or stream bank towards the free face during an earthquake. A series of more or less parallel cracks are formed, separating the ground into blocks.
Ground Shattering
Bedrock or soil on a ridge top that has been thoroughly pulverized due to high accelerations over many cycles of earthquake shaking.
Growth Fault
A fault that moves contemporaneously with deposition causing the throw to increase with depth and the strata to be thicker on the downthrown side as compared to the upthrown side.
Head Scarp or Main Scarp
A steep surface on the undisturbed ground at the top of the slide, which is the upper slip surface.
Hydrocompaction
The process whereby soils collapse when they are wetted, it may also be called hydroconsolidation.
Inactive Fault
A fault without recognized Quaternary displacement, based on direct geologic evidence of inactivity.
Intensity
A measure of the effects of an earthquake at a particular place. Observed effects are the damage to human structures, ground disturbances, and animal reactions. Subjective.
Intensity Scale
A descriptive way to assess earthquake intensity. The scale sued is the Modified Mercalli Intensity Scale
Lateral Spread
Movement of a fractured mass laterally, often along a basal shear surface or zone of plastic flow.
Liquefaction
The sudden large decrease of shearing resistance of a cohesionless soil caused by a collapse of the structure by a shock (such as an earthquake), and associated with an increase of pore pressure.
Lithosphere
Composed of the Earth’s crust and part of the upper mantle, it is approximately 100 km thick and is relatively strong as compared to the underlying asthenosphere.
Local Magnitude
Local or Richter magnitude is the log10 of the maximum seismic-wave amplitude ( in 0.001 millimeter) recorded on a standard seismograph at a distance of 100 kilometers from the earthquake epicenter.
Magnitude
A measure of the strength of an earthquake or the strain energy released by it. Four common types are Richter (or local), body wave, surface wave, and moment magnitude.
Microseism
A more or less continuous motion in the Earth unrelated to earthquakes, with a period of 1-9 seconds.
Moment Magnitude
The magnitude of an earthquake estimated by using the seismic moment.
Peak Ground Acceleration
The maximum ground acceleration experienced by rock or soil during the course of earthquake motion.
Period
The interval of time required for the completion of a cyclic motion or recurring event.
Recurrence Interval
The average time interval between earthquake occurrences of equal magnitude on the same fault.
Richter Magnitude
The common term for magnitude regardless of how it is measured. Was developed ot be able to assign one numerical value to an earthquake that would represent an absolute measurement of its size.
Rigidity
The ratio of the shearing stress to the amount of angular rotation it produces in a rock sample.
Rotational Slide or Slump
Landslide movement due to forces that cause a turning moment about a point above the center of gravity of the unit the slip surface is concave upwards.
Sand Boil / Sand Volcano
A cone-shaped deposit of sand formed during an earthquake when subsurface sand layers liquefy and then are blown to the surface through cracks.
Seiche
A wave oscillation of the surface of water in an enclosed basin (such as a lake or bay) initiated by an earthquake or changes in atmospheric pressure.
Seismic Gap Theory
A theory that forecasts location and magnitude of future earthquakes based on the absence of earthquakes in one area as compared to the presence of earthquakes adjacent to the gap.
Seismic Moment
A measure of earthquake size that depends on the rock rigidity, amount of slip and area of rupture. Based upon a measure of the three-dimensional volume of the slipped fault. Moment Magnitude is most accurate in the magnitude range above 6.
Settlement
The gradual downward movement of a structure due to compression of the soil below the foundation.
Slow Earthquake
Fault displacement that occurs over a time span of days to months without an accompanying earthquake.
Soil Creep
The gradual, steady downhill movement of soil and loose rock material.
Subsidence
A localized mass movement that involves the gradual downward settling or sinking of the Earth’s surface.
Surface-Wave Magnitude
Magnitude of the an earthquake estimated from measurements of the amplitude of surface waves.
Toe
The outermost margin of displaced landslide material farthest away from the head scarp.
Topple
Slope movement due to forces that cause an overturning moment about a pivot point below the center of gravity of the unit.
Translational Slide
Landslide movement that occurs predominantly along planar or gently undulating surfaces.
Triggered Creep
Creep that occurs on a fault which has been triggered by a strong earthquake on some other fault.
Tsunami
Gravitational sea wave produced by large-scale, short-duration earthquake on ocean floor, submarine landslide, volcanic eruption, or asteroid impact.
Where do 95% of all earthquakes occur?
At the plate boundaries and are tectonic in origin.
What are earthquakes caused by?
-Tectonics
-Volcanics
-human activities (filling reservoirs, injection wells and nuclear test)
How are earthquakes classfied?
Shallow 0-44mi
Intermediate 44-190 mi
deep >190
Where do most earthquakes originate?
About 70% are shallow and crustal. Most originate in the top 15 miles. All of the deep earthquakes occur in subduction zones.
Elastic rebound theory
-States that the crust is locked or is slowly being displaced along the fault.
-The crustal rocks behave as an elastic material, slowly deforming in response to the fault movement.
-Deformation continues until strains exceed the strength of the rocks and the rocks rupture.
-The break is followed by an elastic rebound of the rocks on either side of the fault to new positions
-During rupture, the rocks release the elastic energy accumulated during strain
-The stored elastic energy is released partly as heat and partly as an earthquake.
What depth is the overburden pressure about equal to the strength of the rocks?
At 3.1 miles, with no other factors operating, if rocks at this depth were sheared, the rock would not behave as an elastic substance, but would deform plastically. Yet, earthquakes rupture rocks at this and great depths.
Dilatancy
The volume increase in rocks as the pressure is applied, water is less compressible and the rock actually incases in volume. As the rock dilates, it weakens the fault zone and the water reduces friction along the fault, allowing it to slip.
Two types of seismic waves generated by an earthquake
body waves or surface waves
Body Waves
Are propagated within a body of rock and consist of a faster wave called the P wave (or Primary) and a slower S wave (or secondary). Earthquake waves travel an order of magnitude faster through more rigid materials like rock than in sand, silt and clay.
P wave
Transmitted through the rock by a series of compressions and dilations, just as a sound wave is transmitted. Travel at speeds directly proportional to the resistance of the solid material to compression and shear and inversely proportional to the density of the material.
S wave
shear the rock at right angles to the direction of travel and cannot travel in liquids.
P waves travel compared to S wave
1.7 times faster. Amplitudes and wave lengths vary depending on the subsurface conditions.
Surface Waves
those waves that move only near the ground surface. Wave displacements are greatest at the outside surface and diminish downwards.
Two types of surface waves
Love (L) waves and Rayleigh waves.
Love waves
move the ground from side to side in a horizontal plane but at right angles to the direction of propagation of the seismic wave. The horizontal shaking is particularly damaging to the foundations of structures.
Rayleigh waves
motion is similar to an object floating in the surf. the motion is in a retrograde elliptical orbit in the vertical plane oriented in the direction of wave travel. The surface waves (Love and Rayleigh) arrive after the S wave and are the most destructive.
Seismograph
invented to measure the movement of the ground during an earthquake. They record the earthquake motions as a function of time, including the times of arrival of the P and S waves. With seismographs from 3 or more locations, the magnitude and epicenter can be determined.
Strong Motion Seismograph or accelerograph
directly measures the ground acceleration. The recorder is at rest until ground acceleration exceeds a preset value and triggers the measurement of the strong motion of a large earthquake.
What does the motion felt during an earthquake include?
Short-period as well as long-period waves.
-With increasing distance or magnitude of the earthquake, the proportion of long-period waves increases.
-This is because shorter periods are attenuated more rapidly, and are thus filtered out.
What happens when earthquake waves pass from bedrock through alluvium to the surface?
Waves are amplified
Which will experience more ground shaking, bedrock or saturated unconsolidated soils?
Saturated unconsolidated soils
Velocities of earthquake waves through different materials.
Increase with density of materials.
How has the methodology for calculating Richter magnitude changed?
no based upon the seismic moment to obtain the moment magnitude.
How much more energy does each magnitude release?
31.6 times the energy of the previous magnitude.
How do you calculate difference in energy release between earthquakes?
Square root of 1000^difference in magnitudes
How were earthquakes measured prior to the richter scale?
Intensity Scales
Level I intensity
Not felt except by a very few under especially favorable circumstances.
Level V Intensity
Felt by nearly everyone, many awakened. Disturbances of trees, poles, and other tall objects sometimes noticed.
To locate the epicenter
several seismogrpah stations record the time difference between the P and S wave arrivals. The difference in P-S travel time in seconds is correlated to the distance from the epicenter by means of a nomograph or alignment diagram. The distance is plotted on a map as the radius of a circle. With a minimum of three stations reporting the epicenter can be located where the three intersect.
The new madrid fault zone
Located in Missouri, Arkansas, Kentucky, and Tennessee. has a high probability of future earthquakes based upon the sand blows that are found throughout the region. Buildings in this region have not been built to seismic standards that exist in California.
Why do earthquakes that occur in Central and Eastern U.S. propagate for much longer than in the Western U.S.?
The crust is “old and cold” here, thereby transmitting the earthquake waves more efficiently.
How does the Nuclear Regulatory Commission define faults?
as one that has moved at or near the ground surface in the past 35,000 years.
How does California Geological Survey define faults?
One that has movement within Holocene time.
Different means of dating Pleistocene and Holocene deposits are:
- 14C and accelerator mass spectrometry (AMS)
- Soil Chronostratigraphy
- Marine terrace correlations
- Tephrochronology
- Paleontology (mammalian and invertebrate)
- Paleomagnetism
- Uranium series analysis
- Amino-acid racemization (AAR)
- Dendrochronology
Hazards created by earthquakes
- Ground Shaking (blind trusts, site-specific events)
- Surface fault rupture
- Ground failures (landslides, liquefaction, lateral spreading, subsidence)
- Triggered water movements (Tsunami, Seiche)
- Aseismic (fault creep, triggered faulting, afterslip)
- Fires
- Building infrastructure damage
In populated areas, what is the greatest potential for loss of life caused by during an earthquake?
Ground Shaking
What factors does the degree of damage from an earthquake depend on?
magnitude, focal depth, distance from the causative fault, source mechanism, duration of shaking, type of surficial deposits or bedrock, degree of consolidation of surficial deposits, high rock accelerations, presence of groundwater, topogrpahy and design, type and quality of building construction.
Why is the hazard caused by a blind thrust eathquake greater than that from a strike-slip earthquake of the same magnitude?
Because the low dip of the trust fault places the fault plane at shallow depths underlying a larger area. Ground motion is therefore more vertical than horizontal. These faults are formed in compressional zones and usually undetected.
When does surface fault fracture usually occur?
Typically magnitude 5.5 and larger, and when the hazard is more localized, also dependent on the type of movement and can create area of uplift and/or subsidence.
Aseismic Fault Slip
A fault creep that occurs without accompanying earthquakes. At or near the surface, in steady or episodic displacement and can be tectonic or induced by human or natural causes.
Transient Creep
occurs when the creep rate fluctuates from the long term rate
How can fault creep movement be monitored?
Alignment arrays, creepmeters, geodolite networks, GPS, and InSAR
Ground Failures
Failures induced by an earthquake that are not expressions of the fault breakage at the surface, but involve loss of strength or failure of the underlying materials. Examples include landsliding of unstable units, liquefaction, lateral spreading, lurching, differential settlement, sand blows and bedrock shattering.
What type of environment do liquefaction, lateral spreading, lurching, sand blows, and differential settlement occur?
Fine-grained, water-saturated valley sediments.
Where does shattering occur?
at the top of ridges
What can cause a Tsunami?
Submarine landslides, earthquakes, volcanic eruptions, extreme weather events, asteroid impacts.
What is the threshold magnitude for the development of a tsunami?
6.5 to 7.5, although these tsunamis are not normally destructive. Magnitude >7.5 are most likely to generate destructive tsunami.
How fast and far can/do Tsunamis travel?
Thousands of miles at speeds up to 400 mph, with run up heights of tens of feet ot over a hundred feet.
Tsunami run-up heights are dependent on what factors?
the local sea-bottom topography and shoreline shape.
What is the main cause of building damage from earthquakes?
Length of time ground motion acceleration lasts. Longer duration accelerations develop higher velocities and higher relative displacements in the structure.
How do soil conditions and building structure type interact?
When the building and soil have the same or similar period of vibration, the building resonates (or amplifies) the ground motion, and damage is more extensive.
-Thus low-rise buildings (< 5 stories) located on shallow soils (< 50 feet) and high rise buildings (>14 stories) on deep soils (>150 feet) sustain the most structural damage.
What is the purpose of a hypothetical earthquake (design basis ground motion)?
To assess the earthquake response of the structure and to design a building that will ahve an adequate factor of safety to withstand the anticipated forces. The design earthquake is the ground motion that has at a minimum a 10% chance of being exceeded in 50 years.
What are the seismic provisions in buildings codes based upon?
A probabilistic method of determining the design earthquake.
What is Seismic Hazard?
the hazard associated with all the natural phenomena surrounding earthquakes - ground motions, fault rupture, ground failures, etc. Seismic risk incorporates the built environment and the population exposure to those hazards.
Alaska has the greatest number of earthquakes per year of any other states, but it does not have the highest seismic risk because it has a smaller population that is not exposed to the hazards the way the population in California is.
What areas are most impacted by landslides?
Mountainous regions of the Pacific coast, the Appalachians, and the rocky mountains
Landslide Triggers
defined as an external stimulus such as intense rainfall, earthquake shaking, volcanic eruption, storm waves, rapid stream erosion, or rapid snow melt.
What are the elements of a landslide investigation?
- Research and review available information on the site and general vicinity to ascertain the history of both the natural and human processes on the site conditions.
- Select an appropriate scale for site mapping and planning for the subsurface investigation of the site and its intended purpose. Locate trenches and/or boreholes to obtain an adequate understanding of the sites subsurface conditions.
- Perform a subsurface investigation and instrument the site to determine the soil/rock properties, depth to the slide planes, groundwater depths, groundwater fluctuations, depth to bedrock or other undisturbed in-place soils.
- Interpret the data obtained and coordinate/consult with soils/geotechnical engineer. Analyze the unstable areas and its relationship to proposed site modifications and develop mitigation measures specific to each individual unstable area.
- Communicate the results of the investigation in a report. All boring logs, trench logs, laboratory and field testing results should be included in the appendices.
What is the primary function of a landslide stability analysis?
to determine the “factor of safety” so that the effect of controllable forces acting on the slide mass can be assessed. If the factor of safety is less than 1 the slope will fail.
What are resisting soil forces?
Cohesive soils
Deep rooted plants with small above ground profiles
More weight on the lower slopes and toe
High coefficient of friction
Normal stresses
Low risk of seismic shaking
Flatter slope angle
Short slopes
Removing water
What are driving soil forces?
Non-cohesive soils
Shallow rooted plants with large above ground profiles
More weight on the upper slope’s
Lower coefficient of friction
Shear stress resulting from weight of soil and rock materials
High risk of seismic shaking
Steeper slope angle
Long slopes
Adding water (thereby adding weight)
Methods of analysis to determine the factor of safety of a slope?
The selection of an appropriate method is dependent upon the potential or actual type of failure surface and type of material and groundwater conditions.
Successful analysis requires a clearly defined slide plane, which requires 3extensive subsurface field work by experienced personnel.
Some of the commonly used methods of equilibrium slope analyses are:
1. Slope stability charts - used for many conditions in which shear strengths of the soils are known or can be evaluated.
2.Detailed analyses are used when the failure does not fit the models for the slope stability charts.
Slope Stability Charts
Used for slope analyses when shear strengths of the soil are known or can be evaluated.
Ordinary Method of slices Analysis (Fellenius Method)
A collection of “slices” of a landslide whose characteristics are tabulated and summed.
Computer Analysis of slope stability
commonly used to perform calculations using the fixed parameters and varying the conditions of equilibrium.
Markland Wedge Analysis
used to determine the stability of rock wedges generated by natural fractures or joints in cut slopes such as road cuts. The structural information is plotted on a stereonet. Planes, such as faults, beds, or joints, plot as lines or arcs. Directed lines such as the lines that forma t the intersections of two planes or an apparent dip and dip direction, plot as points.
Primary objective of landslide mitigation efforts?
Increase the resisting forces or decrease the driving forces.
Common rock slope reinforcement measures
Rock bolts, Dowels, Tieback Walls, Shotcrete, Buttresses
Rock Bolts
Increase the resisting force by stabilizing rock slides and to prevent movement of rock slopes during construction. The bolts hold a reaction plate to the slope. The bolts need to be tensioned and corrosion protected.
Rock Bolt requirements
Rock that is not highly fractured and at the depth of the bolt can provide an adequate anchor.
Dowels
Increase the resisting force. Reinforcing steel rods or dowels are cemented in place. These work best prior to movement and have to be drilled into sound rock.
Tieback Walls
When the rock is highly fractured it may require a concrete wall that is tied in place using bolts as tiebacks. Since the concrete wall acts as the reaction plate for the bolt distributing the load, its important to make sure the concrete does not crack. This method requires drain holes so hydraulic pressures don’t build up behind the concrete.
Shotcrete
Increases the resisting force for highly fractured or degradable rock. This requires the removal of loose blocks, soil and plant matter prior to the installation of the shotcrete so there is a good bond with the underlying rock. For strength of the shotcrete and reducing the likelihood of cracking it requires a mesh or steel fibers as reinforcement. The mesh must be closely connected to the rock or placed between two layers of shotcrete.
Buttresses
Reduces the driving forces by creating a retaining/supporting structure for areas where there are overhangs or voids in the rock face. This effectively retains the unsupported rock. It must be installed on clean stable rock.
Rock Removal Slope Stabilization
Done to remove any and all loose and unstable rock which removes the hazard. This is effective in removing the hazard only if there is stable rock underlying the unstable portion. In most cases these processes are used to protect roadways and the vehicles traveling on them.
Resloping
A resisting force change through increasing stability by making shorter and gentler slopes. Flattening of the slope or reducing the height of the slope by sloping back the overburden, weathered rock, and slide prone materials at the top creating a more stable slope of competent rock. A stable slope created by the resloping process may become less stable over time.
Trimming Slope stabilization
increases stability by removing overhanging rock resulting from slope failures. Very closely controlled blast using explosives is used to remove areas that have become unstable due to failure of rock below creating an overhang.
Scaling Slope Stabilization
Increases stability by removing loose rock and soil on slopes too steep for earth moving equipment. Removal of the unstable rock and soil on slopes that are very steep is performed by hand by workers who are hanging on the steep slopes by a rope and haress setup. Rock and soil materials are removed using hand tools such as scaling bars and shovels.
Minimizing Rock Fall Hazards
This is done to address a situation where the rocks are expected to fall to control the direction and distance of the falling rock. These facilities need to be properly engineered to allow for the calculation of proper dimensions and position of the facilities. Benches slopes usually are not appropriate because of the likelihood of rocks bounding and the inability to properly clear the benches due to damage to the benches.
Ditches - Slope Stabilization
Installed at the toe of the slope to catch falling rocks. The width of the ditch is related to the steepness of the slope as well as the height of the slope. Steep slopes (>75 degrees) tend to have the rocks fall close to the base of the slope and as the slope flatten it goes through bouncing (slopes between 55 and 75 degrees) to rolling down the slope (slopes between 40 and 55 degrees).
Barriers - Slope Stabilization
Often used in conjunction with ditches to keep falling rocks restricted. A wide variety of barriers are used. They need to be able to withstand impacts of rocks without sustaining significant damage. Geofabric and soil layers can also be used and can be reinforced with tires or railway ties.
Gabion walls - slope stabilization
made of wire mesh filled with rocks and can sustain more powerful impacts than the concrete barriers with damage.
Catch Fences - slope stabilization
Provides relatively low cost flexible energy absorbing materials to absorb the energy of the falling rock. Built as fences adjacent to ditches that catch teh rolling rocks and keep them from bouncing onto the roadway. There are a wide variety of methods to install these fences.
Mesh - slope stabilization
Provides a barrier that keeps the falling rock adjacent to the slope so it falls right at the base. Generally made of chain-link wire mesh his is anchored at the top of the slope and draped down the slope for long slopes the mesh can be contained by installing wire rope across the slope to keep the mesh close to the slope.
Sheds or Tunnels - slope stabilization
Provides cover for the roadways when it would be too costly or dangerous to use other methods. Rock sheds are built over roads at the base of steep slopes or ravines to cover the road and direct falling rock over the roof of the shed to accumulate further down the slope. Tunnels are expensive and used as a last resort.
Excavation - slope stabilization
Driving forces can be decreased by removing material from the head area which decreases the total weight or reducing the slope height or slope angle. Placing material at the toe area places the weight low on the slide and increases the resisting forces. Excavation could cause expansion of or be unable to stop the slide, particularly in large planar failures. Removing the support provided by the toe of a landslide could trigger a larger slide. Undercutting can destabilize the ground upslope, further weaking the slope. In areas of especially soft clays, a second deeper failure surface can be triggered by the excavation process.
Removal of material form the head of a slide
Reduces the driving force - Only on rotational slides, ineffective on translation slides or flows.
Reduce slope height
Reduces the driving force by reducing the weight of the soil mass - Usually needed for a roadway crossing a slide mass (the higher up the roadway is in the slide mass the more stable the slope in the road cut).
Excavate and replace the upper portion of the slide mass with lightweight material
Reduces the driving force by reducing the weight of the soil mass - Can be used for limited use traffic areas. Shredded tires or tree slash are commonly used for this lightweight material.
Benching the slope into the slope face
Reduces the driving force - Most effective on shallow failures, useful to provide protection for structures below the slide mass, particularly beneath rockfall-prone cliffs, or for controlling surface drainage.
Flattening the slope
Reduces the driving forces by reducing the weight of the soil mass - Reduces the effect of undercutting by waterways or construction loading.
Plastic Mesh Reinforcement - Strengthening Slopes
Increases stability by adding to the shear strength and thus the bearing capacity of the subsoil. A plastic polymer material, which is a lightweight high-tensile-strength grid of reinforcement material, can be stretched to cover the ground and acts similar to reinforcing mesh in concrete. Added material strength reduces the amount of ballast needed over soft ground.
Rock-fill Buttresses - Strengthening Slopes
Increases stability by increasing the weight of the material at the toe of the slide. Soil or rock materials can be dumped or placed at the toe of the slope to create a counter force that resists failure. Coarse rock or riprap is preferable since it has greater frictional resistance and is free draining.
Stream Channel Linings - Strengthening Slopes
Used to stabilize the stream channels and sides. This reduces impact of debris flows and maintains the channel alignment minimizing the impact on bridge abutments. Lining of the stream channel is by slush grouting with high-quality concrete reinforced with steel fiber mat provides abrasion/erosion resistance. To dissipate the water flow, energy boulders or baffles are set into the concrete. This is most effective if the entire unstable channel is lined.
Check Dams - Strengthening Slopes
Small, sediment-storage dams built across the channel of steep gullies are used to increase stability of very unstable banks. They can also be used to control raveling and shallow slides in the source area of debris slides.
Check dams are preferred for unstable banks. A dam is keyed into the bank, providing toe support which enhances stability. Check dams reduce the channel gradient which in turn reduces the volume of debris available which additionally reduces or eliminates channel scour, reduces destabilization of gully walls and stores debris flow sediment.
Soil Hardening - Soil Strengthening
Adds strength to the soil mass when the materials are generally impermeable.
Electro-osmosis Treatment
Water in the soil is removed by setting up an electric current in the soil mass. The water migrates from an anode to a cathode and is then removed by pumping.
Thermic Treatment
Subsurface materials are baked by hot (1000 degree Celsius) gas introduced downhole in boreholes drilled in a specific pattern.
Grouting Soil hardening Treatment
Grout is injected under low pressure into fissures and replaces water in cracks and along the slide plane. The method works best in a slide mass that has numerous water-filled fissures.
Revegetation - strengthening Slopes
Planting of appropriate vegetation will reduce the volume of groundwater in the slope as well as strengthen the soil materials.
Plants will dry out the upper soils by removing moisture for their use. Plants will reduce infiltration of surficial water and rainfall. Plants consolidate the soil material by developing a root network. Plants with deep roots help tie surficial materials to deeper materials thereby increasing stability.
Low Walls
are used on soil slopes to support the toe or prevent loosening of the soil materials at the toe.
High Walls
are generally used only as a last resort because construction is difficult and expensive.
Crib Walls
Used to retain shallow sheet-type slides. Walls that are in the form of a box that are keyed into the ground to a depth below the slide plane. Generally filled with aggregate to allow drainage or well drained compacted soil to provide weight.
Overbridging
a bridge is constructed over the slide mass, supported by the stable materials outside or below the slide mass. This solution is expensive and is most often used for the support of roadways.
Retaining Walls
Designed to retain soil materials while providing drainage to allow the removal of groundwater from behind the wall.
Retaining Wall Design
With a coarse backfill and a foundation that will allow adequate drainage from behind and drainage away from the wall through the use of subsurface drains. Retaining wall failure often results form the build up of very high groundwater pressure behind the wall.
Timber Crib
Composed of interlocking timbers that is keyed into the ground to below the slide plane. This forces the potential failrue to be deeper and less critical depth. Wall volume should be 10 to 125% of the unstable soil volume. The failure resistance is from the crib strength.
Timber Crib Design
Structure is backfilled with coarse aggregate allowing drainage. The wall must be designed and built to withstand shearing, overturning, and sliding at the base. This is achieved by founding the structure to a depth below the critical failure plane. To be effective the volume of unstable soil should be relatively small and only forma thin layer over stable soil material.
Steel Bin Crib
Composed of bolted together corrugated galvanized steel structures filled with well drained compacted soil materials. Stability is provided by the weight of the wall (mostly the contained soil).
Steel Bin Crib Design
The steel crib must be specifically engineered for the anticipated loads and foundation conditions. Design charts provide the horizontal steel specifications and height-to-width ratios for typical loading conditions. To be most effective the width of walls will be 6 to 15 feet and are ~1/2 of the wall height. To optimize sliding resistance it should be founded 2 to 3 feet below grade. A 6H:1V slope of the wall will increase the factor of safety.
Reinforced Earth Wall
Composed of horizontally interbedded flexible metal strips and compacted soil to form a high strength system.
Reinforced Earth Wall Design
A patented composite earth-metal system designed for constructing very steep to vertical fills without supporting structures at the fill face.
Gabion Walls
A quick, inexpensive, easy way to build a wall that is composed of a stack of 2 to 3-foot high boxlike wire mesh containers filled with 4 to 8 inch cobbles. Stability is provided by the friction between the rows and the friction at the base. Drainage is provided by the high permeability.
Gabion Wall Design
The higher the wall the wider the base needs to be. Sometimes, like where the foundation soils are clayey, a buttress needs to be built into the back of the wall to increase stability.
Piles
Should only be used for shallow slides and is better as a preventative measure in combination with other methods such as subsurface drainage.
Importance of Drainage in Slope Stabilization
Water is heavy and lubricates the soil materials
Surface drainage after slope failure
diversion of surface water is important immediately following any slope failure and on any slope where potential for slope failure exists, without further jeopardizing the slope in question.
-Divert any watercourses or other surface water flow to prevent water from entering the slide mass.
-Grade the slide mass to remove ay depressions or cracks that may have developed during movement or erosion.
-Place drainage ditches to intercept and transport any surface water that may have accumulated on the slide mass.
Smoothing the Site
Site leveling to prevent ponding and providing positive drainage discourages water from penetrating the subsurface materials. Stabilization of the mass results by decreasing hte pore pressure and decreasing the weight of the material.
Ditches for Drainage
Surface ditches are most effective when placed at the head of the slide, where they can intercept surface water before it enters the slide. They should be connected to lateral drains at the side of the slide mass. Ditch gradient should be at least 2% to ensure flow away form the slide mass.
Straw Wattles
(aka straw worms, bio-logs, straw noodles, or straw tubes) are long (20 feet), narrow (8-12 inches), lightweight (30 pounds) tubes of compressed straw that are encased in photodegradable mesh or ties. They are placed parallel to the slope and are designed to intercept surface water to reduce erosion, increase infiltration, and maintain drainage control.
Subsurface Drainage
Installation of a subsurface drainage network may be needed in conjunction with, or in lieu of, grading of the landslide mass. Prior to the design of the subsurface drainage system a geologic investigation, addressing the rock and soil types as well as the hydrogeological environment is required.
Horizontal Drains (Hydroaugers)
are installed in road cuts and unstable slopes to stabilize the slope by removing with water. These can be installed as a drainage gallery.
Horizontal Drains Design
Need to be installed through and below the slide plane. After the holes are cleared of drill cuttings and before the casing is withdrawn, perforated pipe covered with filter cloth is installed with a gradient out of the hill. The rapidity of the improvement in water levels is dependent on the nature of the soil material; clay soils can take up to 5 years to stabilize; sandy soils are more rapid. Half of the improvement occurs in the first year. Once the water levels have stabilized the impact is permanent with minor fluctuations due to seasonal rainfall. Maintenance may be required to keep the drains from getting clogged.
Drains
Shallow subsurface drains intercept water near the surface to prevent it from entering the slide mass.
Drains Design
Perforated pipe and gravel backfill to reduce sloughing of the walls and expedite water flow. Positive drainage of the drains is required. A maintenance program is required to keep ditches and drains clear.
Dewatering Wells
Wells installed to pump water out of a slide mass.
Dewatering Wells Design
Ideally the wells extend to below the slide plane to remove water both in the slide mass as well as below.
What human activities can cause flooding?
Farming, overgrazing, mining, deforestation, urbanization or construction activities, collapse of levees, sea walls or dams.
National Flood Insurance Program (NFIP)
is administered by FEMA, which has identified flood hazard zones and created maps showing the special Flood Hazard Area (SFHA).
NFIP
National Flood Insurance Program
SFHA
Special Flood Hazard Area
Special Flood Hazard Area
Defined as the area of land that would be inundated by a flood with a 1% chance of occurrence in any year, the 100-year flood. Structures within the SFHA have a 1 in 4 chance of suffering flood damage within the life of their mortage.
Where does the U.S. rank for volcanic activity?
Third most in the world, after Japan and Indonesia, with 169 potentially active volcanoes. Alaska has more than 40 volcanoes that have erupted historically. The 1980 Mt. St. Helens eruption is the latest such eruption.
Where does volcanism in the U.S. occur?
In the western states
Where do volcanoes occur?
Most occur at convergent plate boundaries, others at Mid-ocean ridges, and a small number occur over hot spots.
Where are the most hazardous volcanoes?
Those capable of producing large explosive eruptions of silicic magma. These areas are also prone to pumice eruptions, directed blasts, avalanches, pyroclastic flow, mudflows and floods
Hazards associated with volcanoes:
Direct blast
Mudflows (lahars) and debris avalanches
Pyroclastic Flows
Tephra deposit and ash
Lava flows
Floods/tsunamis
Earthquakes
Ground Deformation
Gas and steam eruptions
Directed Blasts
consist of a mixture of hot rock debris, ash, and gases that move at high velocities (up to 375 mph). They complete devastate large areas in a matter of minutes, and could be considered the most destructive volcanic phenomenon.
What are the explosive forces from volcanoes derived from?
The presence of dissolved gas in the magma.
Volcanic Explosivity Index
Rates from 1 (small) to 8 (large) on the basis of the volume of ejecta, the height of the cloud column, and other observed features. The VEI of Mt. St. Helens ranks 5 on this scale.
Subsidence
The sinking or collapse of the land surface.
What can subsidence be caused by?
solution
erosion
oxidation
thawing
lateral flow
compaction of subsurface materials
earthquakes
slow crustal warping
volcanism
hydrocompaction
withdrawal of subsurface fluids
Natural causes of subsidence
formation of a sinkhole over limestone or karst
dissolution of evaporite or salt beds
lava tubes and gravel bed collapse
What soils would you find oxidation soil collapse?
Pear or organic soils since organic soils develop in wetlands faster than it can decompose. As groundwater is withdrawn the peat dries out, oxidizes and collapses.
What type of mining is subsidence associated with?
Coal Mining - about 1/4 of all U.S. land mined for coal has subsided. Coal is often found fairly close to the surface making the risk higher for subsidence. As the coal is mined the support of the overburden may be removed causing collapse.
How does hard rock mine collapse and coal mining collapse usually differ?
Hard rock mine collapse causes large pits as compared to the coal mining which creates relatively gentrl depressions.
Sources for expansive soils
- Expansive clay minerals (smectites) from weathering of volcanic rocks, ash and glass and sedimentary rocks that contain clay minerals.
- Calcium Sulfates (gypsum and anhydrites)
- Iron sulfides (black shales)
What clay minerals are almost always present in expansive soils?
Montmorillonite or other smectite group clay minerals (important preconditions)
Sulfate soils risk to concrete?
Can damage and disintegrate concrete if their presence is not noted. Concrete must be designed to resist the reaction of the sulfate with hydrated compounds in the cement.
What mineralogical methods are sued to identify the types of clay minerals present in expansive soils?
X-ray diffraction
Differential thermal analysis
Microscopic Exam
Volumetric tests to identify expansive soils?
- Free-swell test
- Atterberg limits and colloid content determination
- Direct volume change measurements
Mitigation of expansive soils include the following:
- Avoid them if possible
- Remove and backfill with non-expansive soils
- Treat the foundation
- Apply a confining load (blanket of non-expansive soil)
-Place mat cushions under structure; reinforced concrete piers below expansive soil
- Chemically stabilize soil - hydrated lime or Portland cement minimize swelling
- Isolate water from soil - provide drainage, place impermeable membrane around soil
- Place vertical, deep geo-membranes to minimize moisture fluctuations.
Radon
A radioactive gas that is odorless and colorless that is released from rock and soils. It is heavier than air so it accumulates in building basements. Produced by the decay of U238 and Pb206. An intermediate decay product is polonium (Po218)
Radon Mitigation
Good building ventilation
Radon gas sources
Mylonites and uranium in light colored igneous rocks like granites and rhyolites; black marine shales, and phosphatic deposits; and metamorphic rocks from these sources like gneisses, schists and slates. occassionally found in sandstones and glacial deposits.
What material does Radon gas accumulate in?
Clayey materials because they have higher porosity and the gasses get trapped in the non-interconnected pore spaces. Much of the radon hazard in homes in the U.S. is related to them being built on clayey soils.
Toxic gas and sulfide minerals
can make hydrogen sulfide gas with a rotten egg odor and can be a lethal hazard when emitted suddenly.
Abutment
The sides of a stream channel or a structure that supports the end of a damn or bridge. The right abutment is the side of the channel that is on the right when facing downstream the left abutment is correspondingly on the left.
Berm
A relatively narrow, horizontal bench built along an embankment.
Crown
The roof of a mine.
Cutoff
An impermeable structure placed beneath the base of a dam to prevent or reduce seepage loss. The structure may be made of concrete, compacted clay or grout.
Dam Crest
The flat top of a dam.
Flwoing Ground
Soil that flows into a tunnel from the floor, roof, or walls of a tunnel driven by water seepage. The flow typically consists of cohesionless soil below the water table.
Freeboard
Vertical distance between the dam crest and the water surface of the reservoir.
Grout
A cement slurry of high water content used to seal fissures.
Grout Curtain
A grout barrier used in the vicinity of tunnels or dams where cracks or joints in rocks are filled with a liquid cement that is pumped or poured into spaces to seal them.
Gunite
A dry mixture of Portland cement and sand, forced by compressed air through a special hose, with water applied at the nozzle and sprayed onto mine timbers, tunnel supports, and roadways to seal and fireproof them.
Invert
The floor or bottom of a closed conduit, such as a tunnel, aqueduct or drain.
Lagging
Boards which are joined, side-by-side, lining an excavation.
Phreatic Line
Seepage line. The uppermost level at which flowing water emerges along a seepage face.
Piping
Erosion by percolating water or seepage in a layer of subsoil resulting in caving and the formation of tunnels or pipes through which the soluble or granular material is removed.
Pozzolan
Siliceous or siliceous aluminous materials that when mixed with Calcium hydroxide has cement-like characteristics.
Pressure-Relief Well
Wells drilled at the toe of the dam to reduce the uplift pressure and prevent piping.
Random Zones
Areas within the dam where excavated materials are placed. A random zone is placed where permeability and shear strength are not critical and where weight is important.
Raveling Ground
Rock or soil that drops out of the roof or walls of a tunnel over time.
Riprap
A loose assemblage of broken rocks used for foundations or slope protection.
Running Ground
Soil that runs into the tunnel after removal of roof and wall supports; typically dry cohesionless sand.
Shotcrete
A wet mix of Portland cement, sand, and water, often with coarse aggregate up to about 1 inch (c cm), that is applied through a pneumatic hose onto mine timbers, tunnel supports, and roadways to seal and fireproof them.
Slaking
Disintegration of rock or soil when submerged in water. Outcrops of sound rock when subjected to a shrink swell cycle crumble into flakes or particles.
Spillway
A channel for reservoir overflow.
Squeezing Ground
Soil or rock that creeps into a tunnel and maintains a constant volume.
Swelling Ground
Rock or soil that increases in volume when excavated. Volume increase is usually caused by the presence of clay minerals with a high swelling capacity.
When selecting a site suitable for placement of a tunnel, what geologic conditions should be identified and avoided if possible?
- Large Faults (or cross at the most favorable angle)
- Incompetent formations (deleterious materials)
- Squeezing ground
- Swelling Ground
- Raveling Ground
- Running Ground
- Slaking Ground - High Groundwater and water wells.
- Oil and gas deposits, extreme geothermal heat, mines with sulfide ores, areas of methane gas associated with landfills or coal mines, natural gas fields and formations containing bentonite or anhydrite.
In most cases a tunnel can be designed to address these problems but they have to be recognized and delineated during the investigation phase of a project so they don’t impact the final result.
-What is the most important geologic factor to consider in siting and excavating a tunnel?
Rock condition.
What rock defects should be noted when excavating a tunnel?
discontinuities
faults and shears
weathering and decomposition
Terzaghi Numbers
A method for estimating rock loads for steel arch supported tunnels. Terzaghi numbers rate the condition of the rock from 1 to 9, with 1 being the most intact and hardest rock, and 9 representing swelling rock.
Terzaghi Number - 1
Hard and intact - No tunnel support required
Terzaghi Number - 9
Swelling rock - Circular or yielding ribs on 2-foot centers or less. Rock bolts are not effective. Ribs and lagging must be coated with a waterproof sealant immediately after placement. Over excavate swelling rock.
RMR
Rock Mass Rating
What 6 parameters is the Bieniawski RMR based on?
- Uniaxial compressive strength
- RQD
- Spacing of discontinuities
- Orientation of discontinuities
- Condition of discontinuities
- Groundwater conditions
How are the 6 parameters of the Bieniawski classification system ranked.
Rating numbers
100-81 - very good
80-61 - good
60-41 - fair
40-21 - poor
20-0 - very poor
Adit
Horizontal tunnel opening
Shaft
Vertical tunnel opening
Stope
a dugout tunnel or space that contains the ore that is being mined.
Drift
Horizontal or subhorizontal development openings made in a mine
Winze
A minor connection between different levels in a mine. When worked upward it may be called a raise; when sunk downward it may be called a sump.
Two common methods for tunneling in rock and soil
- Drill and blast
- Boring or continuous excavation methods.
Active Support
support installed under a strain; it is strained to meet the rock.
Passive Support
not installed under strain. The rock must strain to meet the support before any support is provided.
Boring or continous excavation methods
Used primarily for infrastructure projects and include shield methods and tunnel boring machines.
TBM
Tunnel Boring Machines
Tunnel Boring Machines
Create a circular cross-section and carry tunnel support as they excavate. The cost of temporarily supporting the tunnel is saved. Essentially a shielded machine that has a rotating surface or cutter head at its leading edge that excavates the soil or rock. Can accomodate almost any type of rock. If the rock is too hard, drill and blast can be used in conjunction with the TDM.
Shield Boring Methods
Used in soft materials where there is no groundwater or the material is relatively impermeable. The shield is advanced just ahead of the working face in order to provide a protected work area for personnel excavating the face. Continuous support is required in soft ground.
Tunnel Boring Machine Limitations
The cutter head is designed for one rock type so if the rock is highly variable it may make advancement of the tunnel more difficult.
There can be long delays if the TBM breaks down.
Variable Density Multi Mode TBM
Has the ability to excavate just about everything but the expense may outweigh it’s usefulness.
Methods of controlling for shallow groundwater in flow in excavation of tunnels?
Freezing the ground, using compressed air during construction, using penetration grouting, dewatering by pumping from surface wells, or installing a tunnel lining.
Tunnel Liners
Either gunite or shotcrete.
Gunite is a dry mix, that when some water is added at the time of application through the nozzle, can be sprayed on the interior of the tunnel. Gunite is used when a high early strength is needed.
Shotcrete is a wet mix combination of cement, aggregate, and water, mixed before application. It is used when a high quality of concrete is needed.
What are factors to consider when siting a dam?
Landslides
Faults and microseismicity
Seiche potential
Deleterious materials
Underlying geology
Goal of dam geologic investigation?
Provide enough data from which to draw conclusions as to the soundness of bedrock, the possibility of earth movements, and the permeability of bedrock.
Why are aggregate sources nearby aggregate sources important for dam construction?
Transportation of materials is expensive if the sources aren’t nearby. Aggregates need to be appropriate for the dam type.
Concrete dams need aggregate that is non-reactive as in non-sulfate materials and materials that are strong enough to maintain the integrity for the concrete.
It is important to avoid weak materials with high porosities, materials composed of water-based or some reactive carbonates, or materials composed of sulfate minerals.
Earthfill Dam
built from multiple materials that must be available: clay for the impermeable core, earth and rockfill materials for the upstream and downstream embankments, drain rock to drain the downstream embankment, and riprap to protect the upstream side from wave action.
Storage Dam
Used for water storage during the rainy season for sue over the course of the dry season, or for the development of hydraulic head for power generat4ion.
Detention Dam
Used as flood control to catch the water from big storms and release it over time to protect downstream structures from flooding.
Diversion Dam
Used to divert water into other facilities like canals, aqueducts, or irrigation ditches. These usually only divert a relatively small portion of the water in the river.
Debris Dam
Debris that accumulates in rivers after storms can accumulate and create a dam that has not been engineered. These can be very dangerous as they can fail anytime. These dams collect this debris so it can be skimmed off before failure.
Coffer Dam
There are a wide variety of cofferdams that can be used. These temporary dams are used to allow you to remove water from an area that is going to be under construction. The appropriate choice depends on the size of the site and the earth materials.
In designing dams, what is the primary goal?
To seal the flow of both surface and subsurface water traveling down the valley.
Five main engineering geologic considerations when constructing a dam
- Soundness of the foundation materials and their ability to withstand the designed loads and knowing the load bearing potential and load bearing capacity.
- The degree of water tightness of the foundation materials and the measures required to make these materials watertight.
- The effect of prolonged exposure of water on the foundation materials.
- The possibility of earth movement at the dam site and environs.
- Seismic loading potential.
Gravity Dam
Made from Concrete rubble or masonry. A cross-section of this dam perpendicular to the axis of the embankment is wide at the bottom and narrow at the top relying on the weight of the materials for its stability.
Arch Dam
Made from concrete. In plan view this dam is narrow and curved. The ends of the dam embankment are notched into both abutments so that the load of the water behind the dam will be distributed into the abutments.
Buttress Dam
Made from concrete, timber or steel. This type of dam has a thin slab of concrete that is sloped upstream and is supported by perpendicular buttresses on the downstream side that are composed of concrete, timber or steel.
Embankment Dam (Earth Fill)
Made from earth and rock. A cross section of this dam perpendicular to the axis of the embankment reveals a very wide cross-section (much wider than gravity dams). It is composed of a clay core in its center to inhibit water flow through it and upstream and downstream earth and rock materials to keep the clay core protected and in place.
Benefit of embankment dam compared to concrete dams
Can be built on a wide variety of foundations because they have a lower bearing-strength requirement than concrete dams. Minor settlement of the dam foundation does not create serious problems because the dam is able to adjust to minor movements.
Where is the major water load transmitted in Concrete arch and dome dams?
the abutments and thus it is critical that the foundation materials are competent to sustain or resist loads. These dams are therefore usually constructed in deep mountain gorges where aggregates may not be available.
What is the safest and least likely dam to fail?
A gravity or gravity arch dam since they are substantially wider at the base than at the top. They are built with a low center of gravity so they will not topple if support is not provided.
What causes the highest rate of dam failure?
overtopping.
What is a common cause of failure in concrete dams?
foundation problems
What is a common cause of failure in earth fill dams?
piping and seepage.
What is the most likely dam to fail?
Earthfill account for 58% of all dams and 74% of all dam failures.
What dam has the highest rate of failure?
Concrete buttress dams
Potential for dam failure can be analyzed by this equation?
Mohr-Coulomb equation
Materials used as grout
Neat cement, mixtures of cement and sand, or cement admixed with bentonite or other clay. Chemical or bituminous grouting may also be used in special cases.
What is the minimum gallons of water needed to hydrolyze one sack of cement producing a slurry weight of 15.6 lbs/gal?
5.2 Gallons
What happens if too much water is used when mixing grout?
Cement will settle out and the shrinkage will be too great. When there is shrinkage there is cracking allowing leakage.
What does bentonite do when added to grout slurry?
reduces the shrinkage.
What do sulfates do to grout?
dissolve it.
Uses of grout
- Improve strength properties of the soil and rock masses
- Improve settlement characteristics
- Grouting to decrease permeability
- Grouting to fill voids to prevent engineering disasters.
Curtain Grout
To eliminate or reduce the horizontal movement of water or contaminants through the ground by creating a wall of grout. The wall is a series of boreholes in a line in which the spacing is determined by permeability. Usually a second parallel line is drilled with the boreholes located in between those of the first line to close any gaps. A third line can be installed if the first two aren’t adequate.
Blanket Grout
To eliminate or reduce the vertical movement of water through permeable formations that are underlying a reservoir floor or to improve bearing capactiy this blanket is created by a series of shallow boreholes in a grid pattern into a permeable leaky formation.
Consolidation Grout
To increase the density of soil or to fill rock mass discontinuities or voids to enhance strength and reduce permeability and deformability. It is accomplished by isolating the area through casing and the use of packers and injecting grout to tie the materials together.
Compaction Grout
To compact the soil to stabilize and reduce differential settlement and to increase the load-bearing capacity. The goal is to stop or prevent settlement or to lift settled structures. This is accomplished by injecting a very viscous grout mix that displaces the soil grains creating a bulb of grout that compacts and uplifts the soil.
Cavity Grout
To fill abandoned mines, karst voids, or other natural cavities underlying engineered structures. The goal is to prevent collapse of the roof of the mine or the top of a underground void and reduce subsidence potential.
Contact Grout
To connect the lining of a tunnel with the surrounding wall rock. Voids could have occurred during construction or as a result of solution in limestone or piping in coarser materials. A special kind of cavity grouting.
Why is grout often used in dam design?
To control seepage and he stability of the dam.
What measures are often used to obstruct or control seepage under a dam?
Cutoff Trenches, Cutoff walls and/or impervious blankets extending upstream.
Why would a grout blanket be used in the construction of a dam?
To reduce permeability and increase strength. Used when the permeable layers extend too deep. How far the blanket is extended upstream depends on the hydraulic gradient and the volume of seepage.
Consolidation Grouting
Another name for grout blanket.
Formula for determining grout hole depth
depth of grout hole = 1/3 dam height + 50 ft
Cement Aggregates
Too little cement and too much aggregates will result in a lot of voids in the concrete making it rough and porous. Too much cement and too little aggregates will result in a concrete that shrinks and is uneconomical.
Suitable cement mix
10-15% cement, 60-75% aggregate and 15-20% water. Higher quality cement is obtained by reducing the water-cement ratio as much as possible.
How does water and aggregate quality affect concrete?
Suitable water for concrete mixes has no prominent taste or odor and must be within specified limits for chloride, sulfate, alkali, and solids. Impurities may cause corrosion of the rebar, affect the setting time and reduce strength and durability.
Suitable aggregates for cement
-Must be proper size, with the proper gradation,
-Must not contain deleterious materials
-Resistant to wear/abrasion
-Resistant to disintegration
-Resist freeze-thaw
Why is a well-graded aggregate optimal in cement?
It results in a reduction of the void spaces.
What are considered deleterious aggregate materials?
Clay, coal, shale, alkali, mica, flaky particles (or specific gravity less than 1.95)
Problem associated with deleterious aggregate materials in cement?
Too soft or too weak to provide adequate strength for the concrete or are not resistant to freeze-thaw because they absorb water.
Problem with silica and some carbonate rocks in cement?
React with the sodium and potassium alkalis in the cement, forming a gel like substance that absorbs water and swells, cracking the concrete and shortening its life.
Test used to determine the resistance of an aggregate to wear or abrasion?
L.A. Abrasion Test also called the Los Angeles Rattler Test. The resulting wear during this test should not exceed 40% by weight.
Mitigation for Reactive Aggregates
- Find a source for nonreactive aggregates
- Limit the alkali content of concrete
- Use supplementary cementing materials
- Lithium compounds
- Natural pozzolans
Anion
A negatively charged ion.
Aphanitic
An igneous rock texture that refers to the grains not visible to the naked eye, and therefore indicative of fast cooling.
Aureole
The zone of metamorphosed rock surrounding an igneous intrusion and showing the effects of contact metamorphism
Bar
A unit of pressure equal to 10^6 dynes/cm^2, approximately 1 atmosphere.
Bowen’s Reaction Series
The sequence of minerals that form in the process of fractional crystallization of a magma, and the inverse stability to weathering.
Burial Metamorphism
A type of low-grade regional metamorphism affecting sediments and interlayered volcanic rocks that has lower temperatures (200 to 450 C), without any influence of orogenesis or magmatic intrusion.
Cation
A positively charged ion.
Chron
An interval of geologic time during which the Earth’s polarity is predominantly the same.
Color Index
A number that represents the percent by weight or volume of dark-colored minerals in a rock.
Contact Metamorphism
Metamorphism associated with the intrusion of an igneous mass. Metamorphic changers are caused principally by heat, but also by magma composition and deformation related to the intrusion. Pressures are relatively low (<3000 bars) while temperatures range from (200 to 1000 C).
Diagenesis
The physical and chemical changes undergone by sediments at low temperatures and pressures.
Dynamic Metamorphism
The process of creating new rocks from old, involving crushing shearing and recrystallization.
Extrusive Rocks
Igneous rocks that have been erupted on the surface of the Earth.
Facies
A mappable, areally restricted part of a rock body that has different fossils or lithology from other contiguous beds deposited at the same time.
Feldspars
The most widespread mineral group in the Earth’s crust.
Felsic
A descriptive term for an igneous rock that has abundant light colored minerals.
Index Fossil
A fossil that identifies and dates the strata in which it is found. It combines a wide geographic range with a narrow stratigraphic occurrence.
Intrusive Rocks
Igneous rocks that have been formed within the Earth by emplacement of magma into pre-existing rocks.
Key Beds
A well-defined, easily identified strata that is distinctive enough to be useful in correlation in mapping.
Mafic
A descriptive term for an igneous rock that has abundant dark colored minerals.
Metamorphic Facies
A set of metamorphic mineral assemblages that have reached chemical equilibrium during metamorphism within a restricted range of temperature and pressure conditions.
Metamorphic Grade
The intensity or rank of metamorphism, measured by the amount or degree of difference between the original rock and the metamorphic rock.
Metasomatism
The process of mineral replacement whereby a new mineral of a different chemical composition grows in an old mineral. Interstitial liquids or gases must be present for solution and deposition to occur.
Mineral
A naturally occurring inorganic substance, usually having an internal crystal structure.
Mineral Assemblages
The minerals that compose a rock, including the different kinds and their relative abundance.
Pelitic
Referring to a rock that is composed of clay or clay sized particles, or derived from metamorphism of a fine-grained sediment.
Phaneritic
An igneous rock texture that refers to grain sizes that are large enough to be seen with the naked eye, and indicating a slower rate of cooling.
Phase Diagram
A representation of the stability of different phases of a system, often plotted with temperature, pressure and composition.
Plutonic Rocks
Igneous rocks that are generally coarsely crystalline (phaneritic) and are formed from large intrusion at depth.
Polymorphism
The characteristic of a mineral to exist in more than one form.
Provenance
The place or origin from which the constituent materials of a sedimentary rocks or facies are derived.
Regional Metamorphism
Metamorphism acting over large areas resulting from applied pressures of 3000 to 10,000 bars and temperatures of 400 C to 800 C. regional metamorphism is also referred to as dynamothermal metamorphism.
Regression
The withdrawal of the sea from land.
Rock stratigraphic unit
A rock unit that is characterized by a particular lithology and stratigraphic position. A synonym is Lithostratigraphic Unit.
Sessile
A plant or animal that is attached and cannot move.
Silicates
Compounds whose crystal structure contain SiO4 tetrahedra, either isolated or joined to form groups, rings, single or double chains, sheets or three-dimensional frameworks.
Solid-Solution Series
A series of minerals of identical structures that contain a mixture of two or more elements over a range of proportions.
Test
The external hard part of an invertebrate.
Time Stratigraphic Unit
A rock unit that is characterized by formation during a specific period of time and serves as a reference for all rocks formed during the same time period. a synonym is Chronostratigraphic Unit.
Transgression
The advance of the sea onto land.
Twinning
The intergrowth of two or more crystals in a symmetrical way.
Type Locality
The place where a geologic feature (such as a fossil species) was first recognized and described. It contains the type section.
Type Section
The originally described strata that constitutes a stratigraphic unit to which other parts of the unit may be compared. It is preferable to describe the location where the unit atains its maximum thickness and where the top and bottom unit are exposed.
Ultamafic
An igneous rock composed of 90% or more of mafic minerals.
Volcanic Rocks
Igneous rocks that are generally finely crystalline or glassy, resulting from volcanic action at or near the Earth’s surface, either ejected explosively or extruded as lave.
Zeolites
A large group of hydroaluminosilicate minerals that are analogous in composition to the feldspars. They occur in basalt cavities, saline lake and deep sea sediments, and volcanic tuff. They are used as water softeners or desicants.
Zoning
A variation of composition of a crystal, characteristic of feldspars. The interior or center is formed by a high temperature phase, while the exterior or margin is formed by a low temperature phase.
Most common minerals in the mantle
Olivine and pyroxene
Seven Crystal systems
Cubic
Tetragonal
Hexagonal
Trigonal
Orthorhombic
Monoclinic
Triclinic
Cubic Symmetry
4 three-fold axes
Tetragonal Symmetry
1 four-fold axis
Hexagonal Symmetry
1 six-fold axis
Trigonal Symmetry
1 three-fold axis
Orthorhombic Symmetry
3 two-fold axes
Monoclinic Symmetry
1 two-fold axis
Triclinic
1 one-fold axis
Mohs Hardness Scale Equivalents
- Talc
- Gypsum
- Calcite
- Fluorite
- Apatite
- Orthoclase
- Quartz
- Topaz
- Corundum
- Diamond
Relative Hardness of a fingernail
2.5 - Would cut gypsum but not calcite
Relative Hardness of a Copper Penny
3.5 - Would cut calcite but not fluorite
Relative Hardness of a Pocket Knife
5.5 - Would cut Apatite but not Orthoclase
Relative Hardness of a Steel Knife
6.5 Would cut Orthoclase but not feldspar
Luster
property of light reflection from the mineral surface (metallic, glassy, vitreous, pearly, resinous, silky or dull)
Igneous rocks comprise how much of the continental curst?
About 75% and approximately 90% of the oceanic crust.
What is the most widely distributed volcanic rock?
Basalt
What is the most common intrusive rock?
Gabbro
Extrusive equivalent of granite
Rhyolite
Extrusive equivalent of granodiorite
dacite
Extrusive equivalent of monzodiorite
Andesite
Extrusive equivalent of gabbro
Basalt
Varves
The annual rhythms of the accumulation of sediment layers in a lacustrine environment are called
Mafic minerals that igneous rocks are classified by
Biotite, Hornblende, pyroxene and olivine
What are most mafic rocks composed of?
Olivine and pyroxene
Common examples of plutonic ultramafic rocks
Dunite, Peridotite, pyroxenite and hornblendite
What are mafic rocks predominantly composed of?
Dark minerals like pyroxene and olivine with plagioclase
Example of Ultramafic volcanic rock
Komatiite
Alkali Feldspars
Contain Sodium or potassium but little calcium
Plagioclase Feldspars
Contain various percentages of calcium and sodium but no potassium.
Which feldspar forms the solid solution series from Albie to Anorthite?
Plagioclase Feldspar, which means that it has more than one composition because elements substitute for each other within the solid.
Compositions intermediate between albite and anorthite are formed by the substitution of…?
Na Si for Ca Al with the degree of substitution dependent on temperature and pressure.
Frothy
Lots of dissolved gases
Vesicular
Contains dissolved gases
Pegmatitic
High water content
Feldspathoids
Are a group of relatively rare rock-forming minerals that consist of aluminosilicate or sodium, potassium or calcium but have too little silica to form feldspar. Never found in the same rock as quartz. Chemically related to feldspars and take the place of fledspars in igneous rocks that are undersaturated with respect to silica.
Plutonic equivalent to rhyolite
granite
Plutonic equivalent to dacite
granodiorite
Plutonic equivalent to trachyte
Syenite
Plutonic equivalent to latite
monzonite
Plutonic equivalent to andesite
monzodiorite
Plutonic equivalent to basalt
Gabbro
Volcanic equivalent to gabbro
basalt
Volcanic equivalent to monzonite
latite
Volcanic equivalent to syenite
trachyte
Volcanic equivalent to granite
rhyolite
Felsic rocks are mostly…
feldspar, quartz and very few mafic minerals
Minerals in the feldspathoids group include….
leucite, nepheline, sodalite, hauyne, lazurite and melilite.
Mafic lava viscosity
More viscous, less explosive
Felsic lava viscosity
Less viscous, more explosive
Observations that refute Bowen’s reaction series
- Large bodies of granite and granodiorite would need 10 times their volume of basaltic magma form which to have been differentiated.
- Intermediate rocks such as diorite are relatively rare.
- Contacts of plutons suggest other processes at work (Possibly metamorphic origins)
- Oceanic basalts do not show differentiation
- Granites are restricted to continents, batholiths or folded mountain ranges
- The length of time required for settling of small crystals into a segregated layer is infinite.
Volcanic igneous rocks in order of decreasing Calcium
Basalt
Dacite
Andesite
Rhyolite
Trachytes
Alkali-Feldspar
Plutonic igneous rocks in order of decreasing Calcium
Gabbros
Diorites
Granodiorite
Monzodiorite
Monzogabbros
Granite
Monzonites
Synites
Alkali-feldspar
The sedimentary crust is composed of Shale, sandstone and limestone, what is the percent breakdown of these rock types?
Shale - 66.5%
Sandstone -19%
Limestone - 9.5%
Clay size according to Modified Wentworth Scale?
< 1/256mm
Silt size according to Modified Wentworth Scale?
1/256 to 1/16 mm
Sand size according to Modified Wentworth Scale?
1/16 to 2 mm
Gravel size according to Modified Wentworth Scale?
2 to 4 mm
Pebble size according to Modified Wentworth Scale?
4 to 64 mm
Cobble size according to Modified Wentworth Scale?
64 to 256 mm
Boulder size according to Modified Wentworth Scale?
> 256 mm
Sphericity
how close a grain is o being equal in each dimension regardless of how rounded the edges are. A perfect sphere has a sphericity value of 1.0
A well-sorted (poorly graded) sediment has how many sizes present
2 or 3
A poorly sorted (well-graded) sediment has how many sizes present?
More than 3
What does the presence of flute casts suggest?
Sediments that filled depressions on the immediately subjacent bedding plane. Commonly associated with turbidites.
What is a turbidite?
A fine-grained sediment that gradually changes from coarse to fine grained and that was deposited by turbidity currents.
How do turbidites form?
Sudden underwater landslides send a slurry of gravel, sand and silt down a slope. As the mixture reaches a nearly level seafloor, the flow slows down and rocks begin to settle to the bottom.
What is an Arenite?
A well-sorted sandstone with rounded grains and no feldspar.
What is a wacke?
A poorly sorted sandstone with a matrix of silt and clay.
What is an arkose?
A sandstone with more than 25% feldspar.
What is a graywacke?
When lithic fragments of iron and magnesium minerals and feldspar are present along with quartz sand and silt.
How are shales defined?
Consist of at least one-third clay minerals.
Industrial uses of shale?
Bricks, tiles, china, pottery and Portland cement.
Common chemical sedimentary rocks?
evaporites (gypsum, anhydrite, halite), dolomite, phosphate rocks (apatite), manganese nodules, and ironstones (limonite, siderite, and chlorite silicates). Limestones may be considered to have a chemical origin, but most have a biological component to their formation.
Chemical formular for Dolomite?
CaMg(CO3)2
How is dolomite formed?
Precipitated directly from waters in highly saline tidal flats. Saline water in the pore space is enriched in magnesium ions due to evaporation. some of the excess magnesium is exchanged for calcium in calcium carbonate, converting it to dolomite. The conversion is a diagenetic process that usually increases the porosity, making dolomites good reservoir rocks for petroleum.
As sea water evaporates, what is the sequence that minerals are formed?
First is calcium carbonate (calcite), calcium sulfate (gypsum or anhydrite), sodium chloride (halite), magnesium sulfates and chlorates and finally sodium bromide and potassium chlorides.
Common biochemical rocks?
Limestone, apatite, coal, diatomite, and some cherts.
Chemical deposition of calcium carbonate is controlled by the equilibrium reaction:
Ca++ + 2HCO3- = CaCO3 + H2CO3
Calcium carbonate is formed how?
1) Accumulations of limey sand and muds from chemical precipitation or 2) may form from calcium carbonate secreting organisms. Carbonate sediments formed by chemical precipitation are rare compared to the carbonate sediments generated by biological means.
Two forms of calcium carbonate can precipitate:
- Calcite (hexagonal)
- Aragonite (orthorhombic)
These are polymorphous, which means they have the same chemical formula but different crystal structures.
Carbonate Ooze
Formed by foraminifera. Forams extract calcium carbonate from seawater for their shells. After they die their shells fall down and accumulate as ooze at depths of less than 13,000 feet. At greater depths, foraminiferal oozes are rare.
Calcium carbonate compensation depth and what it tells us about carbonate sedimentation?
the 13,000 foot depth that foram shells dissolve as they move below this point. Therefore implies the carbonate sedimentation takes place in warm, shallow tropical waters that are slightly supersaturated with respect to calcium carbonate.
Diatomite
Silica ooozes secreted from diatoms (green algae), radiolarians, or sponges become consolidated and form diatomite. Can be found in oceans where there is little detritus supplied from land and also in freshwater lakes.
Chert
An amorphous or extremely find-grained silica found in concretions and beds. It originates in coastal waters and can be formed by silica-secreting organisms or enrichment of silica in seawater from volcanic rocks.
Pyrite
Formed by the indirect action of bacteria. These bacteria chemically change sulfur from an oxidized state (sulfate - SO4) to a reduced state (sulfide - S). The bacteria can only grow in the absence of oxygen. An environment without oxygen is created when organic matter decays and consumes oxygen.
How is hydrogen sulfide produced?
The chemical change of sulfate (oxidized state) to sulfide (reduced state) releases energy to the bacteria and hydrogen sulfide is produced. Hydrogen sulfide gas changes ferric iron to ferrous iron and precipitates pyrite.
Peat to Coal
Peat is formed when decaying vegetation does not have enough oxygen. Plant fossils indicate peat is formed in freshwater swamps. After burial and chemical transformation peat becomes lignite. More time, deeper burial, and higher temperatures convert lignite to bituminous, and ultimately to anthracite coal.
facies
a mappable, areally restricted part of a rock body that has different fossils or lithology from other contiguous beds deposited at the same time.
styolites
develop from pressure solution as carbonates undergo diagenesis. They are saw-tooth like structures of insoluble residues of low permeability left behind when calcium carbonate dissolved.
Slate characteristic minerals
mica, chlorite, quartz
Phyllite and schist characteristic minerals
mica, chlorite, quartz and feldspar
Schist original materials
gabbro, basalt, ultrabasics, tuff, shale, sandstone
Gneiss characteristic minerals
quartz feldspar mica and hornblende
Gneiss original materials
siliceous igneous rock, rhyolite, tuff, sandstone
Migmatite characteristic minerals
quartz, feldspar, biotite, and hornblende
Migmatite original material
igneous and metamorphic rocks
Mylonite characteristic minerals
quartz and feldspar
Skarn original material
limestone and dolomite
Skarn characteristic minerals
Ca-rich silicates, also Mg- and Fe- silicates
Argillite original material
mudstone, with only slight recrystallization
Greisen original material
Granitic rock
Greisen characteristic minerals
quartz and muscovite
Greenstone original material
Mafic igneous rocks
Greenstone characteristic minerals
prehnite-pumpellyite, or greenschist facies minerals
Serpentinite original material
Peridotite
serpentine characteristic minerals
serpentine, talc, chlorite
Amphibolite original material
basic igneous rocks, occasionally shaly limestone
Amphibolite characteristic minerals
hornblende and plagioclase
Granofels (Granulite) Characteristic rocks
basement gneisses or igneous orcks
Granofels (Granulite) Characteristic minerals
quartz, feldspar, pyroxene, and garnet, little mica
Eclogite Original Material
Basalt
Eclogite characteristic minerals
almandine-pyrope garnet and jadeite-diopside
Sequence of contact metamorphic rocks that form under low pressures
Albite-epidote Hornfels
Hornblende Hornfels
Pyroxene Hornfels
Sanidinite
Sequence of rocks formed by regional metamorphism in order of increasing grade.
Zeolite
Prehnite-Pumpellyite,
Greenschist
Amphibolite
Granulite
Glaucophane schist or blueschist
Ecologite facies
Difference between greenschist and blueschist facies
Greenschist forms at higher temp lower pressure while blueschist forms at higher pressure lower temperature.
Zeolite Mineralogic Characteristics
Laumontite and Heulandite are common mineral assemblages ;
Quartz + Laumontite + Chlorite is diagnostic
Prehnite-Pumpellyite Mineralogic Characteristics
Prehnite + Pumpellyite + quartz is typical. Forms Metagraywackes
No zeolites, glaucophane or lawsonite.
Glaucophane Schist or Blueschist
Determined by the minerals glaucophane and lawsonite and the absence of zeolites, prehnite, pumpellyite, albite and biotite.
Jadeite + quartz is diagnostic of facies.
Greenschist Mineralogic Characteristics
Blueschist minerals are absent.
Albite + epidote + chlorite + actinolite + calcite are diagnostic of the facies.
Where do greenschist facies rocks form?
Under regional metamorphic conditions of moderate temperatures and moderate pressures.
What are the most voluminous and widespread of all metamorphic rocks?
Greenschist Facies which includes slate, phyllite, fine-grained schist and quartzite, sepentinite and greenschist.
Where do the blueschist facies form?
Tectonically active subduction zone environment along the continental margin. Creates a low temperature high pressure environment.
Where do the zeolite and prehnite-pumpellyite facies form?
Result from the burial of greywacke, shale and mafic volcanic rocks in a subduction zone. Forms over a range as pressures increase with zeolites forming first then progressing to prehnite and pumpellyite.
Characteristic minerals and rocks of Amphibolite facies?
hornblende and plagioclase, epidote, almandine, kyanite staurolite and sillimanite.
Commonly results in micaceous schist and gneiss, quartzofeldspathic schist and gneiss, medium to course grained quartzite and marble.
Setting for the formation of granulite facies?
Deep seated regional metamorphism in the deepest parts of the continental crust.
Highest grade of metamorphic rock formed at normal geothermal gradients?
Granulite Facies
Typical granulite facies rocks?
hypersthene granites (charnockites), granodiorites, Quartz-hypersthene gabbros (quartz norite), scapolite-diopside-quartzofeldspathic gneisses, garnet-cordierite-K-feldspar-quartz gneisses, and marble.
Ecoligtie facies form under what conditions?
Very high pressures and varying temperatures.
Ecoligtie mineral composition?
Bimineral composition of omphacite and garnet. The bulk chemical composition is essentially that of basalt.
Granitic intrusions produce what rocks through contact metamorphism?
hornblende-hornfels near the intrusion and lower grade albite-epidote-hornfels facies further away.
How do regional and contact metamorphic rocks differ?
Regional rocks often display foliation, while contact metamorphic rocks are often massive and contain porphyroblasts and usually finer grained than regionally metamorphosed rocks.
Common contact metamorphism accessory minerals?
Magnetite, ilmenite, pyrite, sphene, zircon, apatite, and tourmaline.
Asbestos
A naturally occurring fibrous silicate mineral that is found in serpentines and amphiboles.
What asbestos mineral is found in serpentine?
Chrysotile
What asbestos mineral is found in amphibole?
Tremolite, amosite, anthophyllite, actinolite, and crocidolite.
What is the most dangerous form of asbestos?
Crocidolite because the fibers are small and easy to inhavel.
What two common minerals are often associated with asbestos?
Talc and vermiculite
What mineral can be substituted for asbestos?
Wollastonite and other types of fibers.
What asbestos mineral comprises a large portion of the asbestos used in building materials in the U.S.?
Chrysotile (Mg3Si2O5)(OH)4
What asbestos mineral is used principally as a fire retardant?
Amosite
Trace Fossils
are evidence of the presence of organisms but without leaving the parts of the organism, such as burrows, nests, footprints, or droppings.
Why are most fossils marine in origin?
The marine environment is a low energy environment that allows time for burial to preserve the animal.
When did the fossil record explode and why?
The Cambrian because harder body parts were developed which had a better chance of being preserved.
What makes an ideal index fossil?
Easily identified, distinguishable from other fossils, abundant, widely distributed, lived in different environments, evolved rapidly and lived for a short geologic time.
Examples of useful index fossils and what period they represent?
Brachiopods - Paleozoic
Graptolites - Ordovician
Ammonites -Late Paleozoic / Cretaceous
Mollusca Phylum - Mesozoic / Cenozoic
Fossil Assemblegaes
groups of animals that lived at the same time and place. Groups of several fossils are more useful for corrrelations because there is a greater opportunity for several parts of the assemblage to be present than a single species.
Taxonomy
Domain, Kingdom, phylum, class, order, family, genus and species
(Do keep pots clean or family gets sick)
What is the largest animal phylum?
Arthropoda (arthropods) Have external skeletons, segmented bodies, and jointed appendages. Included in this group are spiders, insects, scorpions, crustaceans, millipedes, centipedes, and trilobites. Arthropods have existed since the Cambrian
What is the second largest animal phylum?
Mollusca - invertebrates with three basic parts: a foot, a visceral mass and a mantle. Many species in this group also have a chitinous shell. Mollusks have been present in the fossil record since the Cambrian to present and form the most abundant index fossils.
What are the three major classes of Mollusca?
Gastropods - snails and slugs
Cephalopods - squid, octopus
Bivalves - clams, oysters, scallops
Why are graptolites important index fossils?
Lived in the Ordovician and Silurian and die out by end of devonian
Why are fusilinids (foraminifera) excellent index fossils?
One of the shortest lived organisms from Pennsylvanian to Permian.
Plankton
Any drifting organism in the pelagic zone.
Why are phytoplankton important?
The smallest plankton and form the foundation of the ocean’s food web and have a key role in the transfer of carbon dioxide from eh atmosphere to the oceans. They consume carbon dioxide and release oxygen making up to 90% of the Earth’s oxygen.
Pelagic
habitat that is within the column of water of the ocean
Benthic
Habitat that is found at the floor of the ocean.
Globigerina Bulloides
A climate indicator fossil. a marine protozoan (foram) that makes calcareous ooze and has been present since the Eocene. Exponential increases in Mg relative to Ca in the shell indicate increasing ocean temperatures.
Catastrophism
Geologic features result from a series of sudden, short-lived, violent events.
Gradualism
Geologic change occurs slowly over long periods of time.
Uniformitarianism
The natural laws that impact the Earth now are the same as those acting in the past. The present is the key to the past.
K-T Boundary Extinction Event
Chicxulub crater formed by asteroid impact; iridium found in sediments. Massive flood basalts erupted from Deccan Traps, India. Killed Dinosaurs and other land creatures, also mass extinctions in the oceans.
Triassic-Jurassic Boundary Extinction Event
Massive volcanic eruptions triggered the opening of the Atlantic Ocean. May have led to global warming. Killed about half of marine genera.
Permian-Triassic Boundary Extinction Event
Massive lava eruptions from Siberian Traps ignited coal seams; coal ash polluted land, air and water. Earths worst extinction event killing 95% of all species.
Ordovician-Silurian Boundary Extinction Event
Glaciation led to sea level drop, followed by glaciers melting and flooding. Killed 60% of marine genera.
Biostratigraphy Stratigraphic Correlation methods
The correlation of rock units and the assignment of relative ages through the use of fossil assemblages contained within the units.
Lithostratigraphy Stratigraphic Correlation methods
Rock units that are recognized and defined based on observable rock characteristics such as chemical composition , grain size, petrology, key beds, structure, etc., and stratigraphic relationships.Chr
Chronostratigraphy Stratigraphic Correlation Methods
Rock units that are correlated based on their age and time of formation.
Magnetostratigraphy Stratigraphic Correlation Methods
Sedimentary or igneous rocks are dated using the magnetic characteristics of the magnetic minerals that record polar reversals.
How old are the oldest dated rocks?
3.5 billion years
How long has the polarity (Brunhes) lasted?
780,000 years
How do you calculate age using half life?
Multiply the number of half lives passed by 5730.
Optically Stimulated Luminescence (OSL)
Measures the last time a mineral was exposed to sunlight. Range is a few hundred to several thousand years.
Thermoluminescence
Buried sediments with radioactivity glow when exposed to LED Light; older ages produce greater light. 1000 - 500,000 years
Accelerator Mass Spectrometry (AMS)
A more precise method of C14 dating that uses a very small sample. Date range is 80,000 years
Carbon 14 Datings
Organic Materials; not useful for marine life. Date range is 50,000 years.
Potassium 40 - Argon 40 Dating.
Applications include the age of mineralization, geologic mapping, faulting, metamorphism, evaporite formation, cooling history of metamorphic rocks. Range is a few thousand to 4.5 by.
Rubidium 87 - Strontium 87 Dating
Used to determine emplacement or cooling ages; Limited use in highly metamorphic terranes. Age range dated is 65 my - 3.8 by.
Radon 222 - Lead 210 Dating
Dates snowfall, recent fresh and marine sedimentation, environmental pollutant rates. Range dated 150 - 200 years.
Uranium - Thorium Dating
Best for precipitated calcium carbonate (stalagmites, travertines, and lacustrine limestones) Range date 1 - 350 thousand
Fission Track U 238 Dating
Yields Cooling ages of apatite, zircon, sphene, mica, tektites, glass. Date range 100,000 - 20 my.
Uranium Lead Dating
Quaternary carbonates and minerals with high U, low Th. Used to determine crustal history and can date several 1000s - 4.5 by.
Tephrochronology
Dating of tephra - Cenozoic to Paleozoic dating
Dendrochronology
Dating of tree rings - 0 - 8,000 years.
How many chrons in the Quaternary and what are the names and dates?
Brunhes - 0 - 0.78 Ma
Maturama 0.78 - 2.59 Ma (Quaternary - Tertiary Boundary)
Divergent Plate Boundaries
Plates are moved apart by molten material of the asthenosphere that is forced up into the crust between the plates and is exhibited as sea floor spreading, such as at the Mid-Atlantic Ridge, or continental rifting.
Transform Plate Boundaries
The plates may slide horizontally past each other along transform faults like the San Andreas on land or transform faults in the ocean between spreading centers.C
Convergent Plate Boundaries
The plates collide or converge on each other in a subduction zone where one plate dives beneath another. Examples are continent-continent collisions (India and Asia), ocean-continent convergence (Cascadia subduction Zone in the Pacific Northwest) and the ocean-ocean collisions (island arcs like the Aleutian Islands).
How thick is the crust?
Under the continents the crust is 30 to 40 km and in some places 70 km.. Under the oceans the crust may by only 5 km thick,
How old is continental crust when compared to oceaninc crust?
Continental crust can be very old (over 4 billion years old), most of the oldest oceanic crust is only 180 - 200 million years old.
Moho Discontinuity
Separation of the mantle from the crust
What orogeny is associated with the assembly of Rodinia?
The Grenville orogeny and formed the folded mountains in eastern North America.
Iapetus Ocean
name given to the ocean that filled in the breakup of Rodinia
What were the orogenies responsible for the Appalachian mountains?
Taconic
Acadian
Alleghanian
When were the Appalachians eroded?
During the Triassic
When did Pangea begin to break up?
Around 200 Ma in the Jurassic. Palisades orogeny.
When were the ancestral Rockies formed?
In the Pennsylvanian and by the end of the Permian the mountains had been worn down.
The Laramide orogeny
Began in the late Cretaceous (80 Ma) and continued through the Early Eocene (50 Ma). Responsible for the Rockies.
Paleosol
An ancient soil that formed in the past. Preserved by burial underneath either sediment or volcanic deposits, which in the case of older deposits have lithified into rock.
Alteration
Any change in the mineral composition of a rock caused by physical or chemical means, especially by hydrothermal fluids. Alteration is milder and more localized than metamorphism.A
Archie’s Law
An empirical relationship between well log resistivity and water saturation and ultimately to hydrocarbon saturation.
Assay
An analysis of the proportions of metal in a n ore. Composition, purity, weight, or other properties of economic interest are tested.
Average Grade
The average quantity or percentage of ore mineral content in an ore body.
Base Metal
A common and chemically active metal (it oxidizes or corrodes easily) - lead or copper for example.
Block Caving
A mining technique that takes advantage of naturally occurring fractures by blasting and collecting the blocks.
Coalification
The process that produces coal of increasing rank.
Cut-off grade
The value of grade below which the deposit is uneconomic.
Density
The mass or weight of a substance per volume that it occupies.
Diagenesis
The chemical, physical or biological change undergone by sediments after its original deposition and during and after compaction and lithification at pressures < 1 kilobar and temperatures between 100 - 300 C. It does not include weathering or metamorphism.
Dispersion
The process by which elements move away from the enriched ore zone.
Dolomitization
The process by which limestone is converted to dolomite by the replacement of calcium carbonate by magnesium carbonate.
Eh
Oxidation potential; the measurement of the potential of a substance to oxidize.
Epigenetic
An ore deposit that originates later than the enclosing host rocks.
Epithermal
Shallow hydrothermal
Exhalite
The chemical product of exhalation; a deposit formed by the interaction of volcanically derived water and sea water with subjacent rocks.
Gangue
Valueless rock or mineral aggregates in an ore; economically undesirable.
Giant Field
A petroleum field containing 500 million barrels or more of recoverable oil; a natural gas field which has a minimum of 3.5 trillion cubic feet of recoverable gas.
Gossan
An iron-bearing weathered product overlying a sulfide deposit.
Grade
A coal classification based on degree of purity.
Hydrothermal
Pertaining to hot water, the action of hot water, or the products of hot water. The term is generally used for all hot water whether or not the water is of magmatic origin.
KB
Abbreviation for Kelly Bushing. Used as a datum by petroleum geologists.
Longwall mining
A mining technique that shears off the coal from the longest wall of the room.
Metasomatism
The process of practically simultaneous solution and deposition of a new mineral in an old mineral by means of interstitial fluids. The replacement occurs at constant volume with little disturbance of structural or textural features.
Pathfinder
A relatively mobile element whose geochemical properties are sued to more easily find a deposit of greater importance or value.
pH
The negative log10 of the hydrogen-ion activity in solution; a measure of the acidity or basicity of a solution.
Play
A geographic area where common geologic factors exist (e.g. stratigraphy) to create petroleum accumulation.
Precious Metal
Gold, silver or minerals of the platinum group
Prospect
A specific oil and gas trap that has been identified. Once drilled it becomes either a dry hole or producing field.
Pyritization
Introduction of, or replacement by, pyrite, a common process of hydrothermal alteration.
Rank
The degree of progressive diagenesis or metamorphism of peat (coalification).
Recovery
a) The percentage of the total ore that is recovered. b) The amount of oil obtained by primary, secondary, or tertiary means.
REE
Rare Earth Elements. There are 17 REE with atomic numbers 21, 39, 57-71
Replacement
A solid-state change in composition of a mineral accomplished by diffusion of new material in and old material out.
Reserves
Deposits that are economically available and may be extracted profitably with existing technology: a subset of resources.
Resources
Naturally occurring deposits in such amounts or concentrations to be minable now or in the future, including reserves.
Retreat Mining
Mining of the support pillars while retreating from the mine.
Room and Pillar
A type of underground mining that excavates rooms leaving pillars for support.
Silification
The introduction of, or replacement by, silica.
Skarn
Silicate rocks of complex metamorphic-metasomatic mineralogy formed in carbonate rocks in a contact metamorphic aureole.
Specific Gravity
The ratio between the density of a substance and the density of water.
Stoping
Extraction of ore in an underground mine by working laterally in a series of levels in the plane of the vein.
Stratabound
A mineral deposit confined to a single stratigraphic unit.
Stratiform
A special type of stratabound deposit in which the ore constitutes a layer or layers in the rock.
Supergene Enrichment
A near-surface process of mineral deposition in which metals are leached by acidic solutions, carried downward, and reprecipitated, enriching the sulfide minerals already present. Copper is the principal ore redistributed this way, but zinc, silver and other sulfides also undergo enrichment.
Syngenetic
A mineral deposit formed contemporaneously with, and by the same processes as, the enclosing rock.
Nonfuel Minerals
Crushed stone, construction sand and gravel.
Mineral commodities
Metalic abrasives; boron, clays, diatomite, gold, helium, iron etc…
Top three produced mineral produced in the U.S. in terms of value
Crushed stone, cement, construction sand and gravel.
Energy Minerals
coal, oil and natural gas
Magmatic Segregation Ore deposit types
Layered mafic intrusions
Anorthosites
Kimberlites
Carbonatites
Ophiolites
Intrusive igneous iron
Porphyry base-metal deposits
Skarns
Hydrothermal iron
Cordilleran veins
Pegmatites
Solution Remobilization Ore Deposits
Quartz-carbonate-gold
Cobalt-gold
Volcanic Ore Deposits
Epithermal
Volcanogenic massive sulfides
banded iron formations
exhalite gold deposits
black shale hosted ores
Regional metamorphism ore deposits
Industrial rocks and minerals
Garnet, emerald, corundum
Uranium
Sedimentary Ore Deposits
Sulfide deposits
Marine black shales and phosphatic shales
sedimentary iron ores
phosphorites
evaporites
manganese nodules
Weathering Ore deposits
Laterites - nickel, iron
Bauxite
Residual manganese
Supergene enrichment ores
Magmatic segregation deposits
Are large- to moderate- scale and include some of the largest petrologic bodies. Produced by differentiation or direct crystallization of magmas. Form in magma chambers and are dep-seated intrusive bodies.
Mafic rocks commonly contain what?
chromite
ilmenite
apatite
diamonds
nickel
copper
and platinum group elements
Layered Mafic Intrusions (LMI) are a major source of what?
Chromium
Nickel
Copper
platinum
titanium
iron
vanadium
tin
sulfur
Anorthosites
Contain titanium-rich ores composed of titanium-bearing magnetite and hematite, rutile or ilmenite. Anorthosites are all Precambrian in age and occur in close relationship to deep faults along old rift zones.
Kimberlites
Diamond-bearing, volatile-rich, potassic, ultramafic igneous rocks dominated by olivine. Formed very deep in the earth and contain subordinate amounts of minerals that are derived from the mantel.
What minerals dominate Kimberlite mineralogy?
Monticellite, phlogopite, diopside, serpentine, or calcite
Carbonatites
Appear to be closely related to kimberlites and composed of at least half of flow-banded calcite, dolomite or siderite. Commonly exploited for rare earths. Young deposits appear to be related to rift environments.
Ophiolites
tectonically emplaced slices of oceanic crust into or onto continental crust. They consist of three layers:
a lowermost section of serpentinized ultramafic rocks
a middle section of thick pillow basalts cut by diabase dikes
covered by a thin upper layer of siliceous diatoms, radiolarian, limey and cherty precipitates and iron magnesium hydroxides.
Deposits associated with Felsic-Intermediate Intrustion
Consist of the base and precious metals associated with Calc-alkaline orogenic belts. Intrusive (diorite-monzonite-granite) and extrusive (andesite-latite-rhyolite) rocks host porphyry base metal deposits of porphyry copper, molybdenum, and tin.
Cordilleran vein deposits
Open-space fillings or replacement in veins. A type of Felsic-Intermediate Intrusion Deposit that forms at intermediate to shallow depths. Ore components are transported hydrothermally and deposited in fractures and fault veins. Many of these deposits are of major economic significance.
What events are associated with Felsic-Intermediate Intrusion deposits?
Most formed during Mesozoic or Cenozoic orogenies, and a map of these would coincide with the location of mountain building and intrusion. Thus deposits are related to rock composition and plate tectonic settings.
What type of deposit does over 40% of the worlds total metal output come from?
Felsic-intermediate intrusions
What are the most important economic deposits associated with Felsic-intermediate deposits?
Porphyry base metal deposits. Have a porphyritic texture and are emplaced at temperatures from 250 to 500 C at moderate pressures.
Porphyry deposits
gigantic hydrothermal systems, ringed by outer zones of lead, zinc, manganese, silver and gold; exhibiting sulfide-silicate zoning and associated with shallow-seated intrusive activity. Where they intrude into carbonates, skarns are formed.
Where do skarns best develop?
Around the borders of small to moderate-sized bodies of intermediate composition (monzonites and granodiorites), and may be adjacent to and extensions of porphyry base-metal deposits.
Limestone skarn deposits are characterized by what minerals?
Grossularite, andradite, wollastonite, tremolite, epidote, and hedenbergite/diopside.
Dolomites skarn deposits are characterized by what minerals?
Serpentine, diopside, humite-chrondite group and other magnesium-rich minerals.
Sandstones skarn deposits are characterized by what minerals?
Generally unreactive, may recrystallize to quartzite.
Shale skarn deposits are characterized by what minerals?
May recrystallize into hornfels with a sugary texture. Shale products are high in alumina minerals and develop biotite, ottrelite, mixa, andalusite, sillimanite, hornblende, actinolite, garnet, scapolite, and cordierite.
What ore minerals are usually found in skarn deposits?
Sphalerite, galena, chalcopyrite, bornite, molybdenite, pyrite, magnetite, and hematite.
Cordilleran vein deposits metal zonation sequence?
Metal zonation from tin (cassiterite) tungsten (hubnerite-wolframite) molybdenum (molybdenite) through copper-zinc to zinc-lead-manganese-silver. May be rich in silver, copper, gold-silver tellurides, silver-lead or zinc.
Pegmatite are an important source of what minerals?
Beryllium, lithium, rubidium, cesium, tantalum, niobium, uranium, thorium, rare earth elements, molybdenum, tin and tungsten. They are also rich in silica, alumina, water, halogens, alkalies, and lithophile elements (lithium, potassium, sodium, rubidium and beryllium)
Solution remobilization deposits
Form from circulating fluids that scavenge metallic ions from adjacent rock lithologies, dissolve, transport and redeposit them in fractures as vein deposits. Quartz carbonate gold veins of the Mother Lode in California have been explained using this theory and the association of quartz-ankerite-gold vein with talk-carbonate alteration in mafic volcanic rocks has been demonstrated to have this origin. Cobalt and Silver-cobalt deposits may have also formed this way.
Epigenetic Deposits of Doubtful Igneous Origin
Created after the host rock was deposited, under low-temperature, low-pressure conditions involving heated aqueous fluids not associated with igneous activity.
Three major types of epigenetic deposits
- Mississippi Valley Deposits (MVD) of lead-zinc
- Western States Uranium - roll-front, humate, and salt-wash
- Athabascan-type unconformity-related uranium
Where do MVDs occur and how do they form?
In structurally passive areas such as the midcontinent craton of the U.S. and form when warm brines containing metals migrate from basins into carbonate sediments at the margins of the basin. Deposits are laterally extensive but thin, indicating that solutions moved laterally, not vertically.
Some ores are of replacement origin, many occur as open-space fillings in solution breccias into which fragments are dropped, and others form in enlarged joints and fractures in carbonates.
MVD Ore deposits
Principal source of lead-zinc deposits. Minerals are low-silver galena, low-iron sphalerite, and barite-fluorite. Gangue minerals are dolomite, calcite, jasperoid and minor silica. Pyrite and marcasite are present in small amounts. Gold and silver are negligible.
Silicification, pyritization, dolomitization, and recrystallization are common alteration effects.
Dolomitization of the host rock is universally observed
What three regions in the U.S. have provided mroe than 90% of the U.S. production of uranium and vanadium and 40% of the world’s uranium reserves.
Roll-front deposits of Colorado and Wyoming, Salt-wash type deposits of Utah, and humates from New Mexico are all epigenetic deposits that form at low temperatures and low pressures.
How do roll-front deposits typically form?
U+4 ions in rocks undergoing weathering are oxidized to U+6 ions which are soluble in groundwater as uranyl carbonate complex ions. When groundwater encounters a reducing environment, uranyl ions are reduced and uranium is precipitated as uraninite, pitchblende, coffinite, and uranium-vanadium minerals.
Subaerial Volcanic Deposits
Formed by the eruption of intermediate to silicic volcanic rocks at temperatures from 100 to 1200 C. As the volcanic rocks are erupted, cooled, and consolidated, epithermal deposits are emplaced predominantly as open space fillings. Many of the rocks show replacement textures. Associated rock types are basalts, dacites, rhyodacites, latite and rhyolites in pyroclastic flow regime.
Where do epithermal deposits occur?
along convergent plate boundaries and are related to orogenic belts. They are also found in or near areas of Tertiary volcanism. There is no observable associated with plutonic rocks and tourmaline, topaz and garnet are absent.
Commonly covered by an iron oxide cap (gossan). The gossan contains pyrite which weathers to limonite and is an indicator of epithermal deposits below.
Sulfosalt ore Minerals
Characteristic of epithermal deposits. Compounds of silver, arsenic, and antimony with sulfur and gold/silver tellurides are common. Native mercury and gold are also found.
Comstock Lode is what type of deposit?
Epithermal deposits forming a gold-silver mine.
Volcanogenic Deposits (Volcanogenic Massive Sulfide)
stratabound deposits formed underwater by volcanic processes and the activities of thermal springs.
Volcanogenic deposit environment
Volcanically heated seawater dissolves elements in the magma and the mineral-rich brine emerges through “black smoker” vents where the sulfides encrust the vent opening. Massive sulfide ore bodies contain deposits of Cu-Ni, Cu-Zn, and Zn-Pb-Ag with economic deposits of iron , gold, tungsten, tin, antimony and mercury.
A substantial proportion of the world’s lead-zinc reserves are found in the black shales.
Exhalites
Deposits formed from the interaction of volcanically heated water, convecting seawater, and subjacent igneous rocks.
Ore components are derived from sea-floor igneous rocks, convected by seawater, and driven back into the underlying rocks and circulated through, heated up and jetted out through fractures.
The exhaled fluids then chemically precipitate into sediments.
Two types of regional metamorphic deposits
- New metamorphic rocks and minerals are formed by redistribution of mineral components due to their increased chemical mobility.
- Deposits in which ore constituents mobilize and re-emplace
What is an important characteristic of chemical sedimentary deposits?
Solubility Contrast in low-temperature aqueous solutions. An ore component must be soluble, transported in solution or as a compound. The chemical precipitation is controlled by the pH and oxidation potential (Eh) of the environment. Once the conditions are right for the precipitation of a compound, it must then be concentrated either by an abundant rate of precipitation or by moderate precipitation in a basin that does not supply much clastic detritus. Biological influences may also be involved.
Types of chemically precipitated deposits
- Sulfide deposits
- Marine black shales and phosphatic shales
- Sedimentary iron ores- oolitic iron, siderite, limonite
- Sedimentary manganese
- Phosphorus deposits
- Marine and lacustrine evaporites
- Manganese nodules
How do sulfide deposits form?
When metal ions are supplied into a depositional basin where reducing conditions exist from decaying organic debris and where clastic sedimentation is nil. The principal sulfides formed are bornite, chalcocite, chalcopyrite, galena, sphalerite, tetrahedrite, and pyrite. Minor amounts of silver nickel, copper, cobalt, selenium, vanadium and molybdenum may be present.
Black and phosphatic shales
Chemically precipitated rocks that form in low-lying stable areas associated with minor unconformities. Metals are found to be enriched in the black carbonaceous marine shales. Adsorption of metals by clay particles and organic precipitation are significant factors in removing dissolved metals from seawater.
Contain uranium, vanadium, silver, arsenic, gold, molybdenum, and other metallic elements. Uranium- and vanadium-bearing black shales also have a high phosphate content.
Oolitic iron ores
Probably the most economically important sedimentary iron deposit. Form in the nearshore marine environment. River water supplied iron which precipitated as ferric oxide and replaced calcareous ooze, fossils and oolites in the early stages of diagenesis.
Linonite
Produced from he biochemical precipitation of iron minerals in a bog.
Phosphorite
Phosphate-rich sedimentary rock containing more than 20% P2O5 forms on continental shelves where deep, cold sea currents upwell and mix with shallow, warm longshore currents. When the cold water is warmed, calcium phosphate is less soluble. Teh water becomes supersaturated with calcium phosphate and apatite precipitates.
What other metals are often associated with manganese nodules?
Copper, nickel, and cobalt
What are the most common placer deposits?
Native gold and platinum. While magnetite and ilmenite are also abundantly found in placers, but are not usually concentrated in economically significant quantities.
How do weathering products form?
Earth materials are acted upon by hydrolysis, hydration, and oxidation reactions that take place at atmospheric pressures and temperatures from 25 to 50 C. The pH and Eh of the environment can determine the resultant type of weathering products.
Weathering Deposits
May have elements that have been dissolved, redistributed and redeposited, or may have been converted from a worthless material toa valuable ore by the change in composition or mineralogy.
Laterites
Soils rich in iron- and aluminum-oxides. Nickel, cobalt and chromium may be present in large enough quantities to be recovered.
Nickel Laterites
Form over serpentine and ultramafic rocks. Topography and weathering conditions can concentrate the nickel 10 to 30 times the concentration in the source rock. A tropical climate that is stable, large ultramafic rock outcrops, gentle slopes, and stable groundwater conditions all contribute to the development of nickel laterites.
Iron-rich laterites
Form over ferromagnesian rocks deficient in silica. Ideal conditions for formation are alternating wet and dry seasons and a subdued topography marked by swales for the iron oxides to collect. Iron laterites are mined as iron ores in only small amounts because they are low-grade and require removal of excess water.
Bauxites
laterites rich in aluminum and low in iron and silica. They form in humid tropical or subtropical environments where the underlying rocks are also rich in aluminum and low in iron and silica, such as syenites and nepheline syenites.
As the feldspars and feldspathoids decompose, kaolinite may form as an intermediate product of the weathering process. Kaolinite is then desilicated to bauxite. The primary bauxite minerals are boehmite, gibbsite, and diaspore.
Three zones of supergene enrichment
oxidized zone
supergene-enriched zone
hypogene zone
hypogene zone
primary ore zone of a supergene enrichment deposit.
Electromagnetic Method for Ore Deposits
detect the electromagnetic field generated by an alternating current that is introduced into the ground. This method is useful to detect high conductivity massive sulfide deposits.
Magneto-telluric method
Measures variations in the Earth’s electromagnetic field to depths of a few kilometers. It relates the resistivity measured in the subsurface to the various rock types present.
Primary Halo
Abnormal patterns that may exist in the rocks, soil, streams, and vegetation. this anomaly will have enriched concentrations of the ore elements compared to the country rock.
Secondary Halos
Usually more widespread than primary halos and therefore serve as markers, or pathfinder elements to the targeted ore deposits.
Common pathfinder elements
Arsenic and Copper. Also silver, antimony, sulfur, gold, lead, zinc, cobalt, molybdenum and nickel.
The extent of secondary halos formed by dispersion depend on what
Topography and groundwater movement. The more mobile elements may have moved the farthest away from the main ore body or may be entirely absent. Their mobility is based upon their ability to dissolve, their density, their ability to form compounds with other elements, and the pH of the environment.
Measured Resources
those that have a well established size, shape, depth, and mineral content obtained form detailed geologic mapping and sampling.
Indicated Resources
have more widely spaced geologic data but enough to assume continuity of geology and/or grade between sampling points.
Inferred Resources
Assumes geologic and/or grade continuity but does not verify it from sampling or measurements.
Lanthanide Series
REE with atomic numbers 57 to 71, 39 and 21. These 17 elements are transitional metals essential for new and developing alternative technologies.
Major problem with REE concentrations
Do not form minable ore deposits like the other metals and are mineralogically and chemically complex. Ores may contain numerous REE that must be extracted with multiple and separate processes adding to the cost and therefore REE are typically obtained as a byproduct of mining other ores.
Also commonly found with radioactive rocks, and therefore usually subject to intense regulation.
What is the most abundant fossil fuel in the nation?
Coal. 22% of the world’s coal reserves.
HAP
Hazardous Air Pollutants
Coal is the resultant product of what
The decay, burial, compression, and diagenesis of plants growing in either fresh or brackish water swamps on the coastal plains, coastal lagoons, estuaries and deltas.
A high humidity and high stagnant water table are necessary to provide the environment which will allow the extensive growth of plant matter.
Coalification
The process of converting plant matter into coal.
peat is formed how?
as plant matter accumulates it starts to decay by the action of aerobic bacteria and reduces in volume to form peat. As the oxygen is exhausted, anaerobic bacteria continue the decay process and covert the carbon and nitrogen compounds into hydrocarbons, acids and alcohols that lower the pH.
gytta
A gel-like material that forms as peat continues to compress from burial, and temperatures slowly rise and eventually when pH is around 4 the anaerobic bacteria die.
This is the material that will become coal.
Final step in coal formation
Gytta is buried sufficiently to attain the temperature of 100 C or more the bituminization process begins. Carbon is concentrated as water, oxygen and hydrogen are driven off.
Macerals
The organic constituents remaining in coal, formed from the plant remains. Subdivided into vitrinite, liptinite, and inertinite. Each maceral type determines the type of fuel that will be produced.
How is coal ranked?
The degree of progressive diagenesis of peat. Also takes into consideration the heating value, fixed carbon content, moisture and volatile matter content.
Also corresponds to burial depth. As coal becomes more deeply buried the rank will increase because the temperature and pressure increase. (increasing the temperature is thought to be more important in the coalification process). In general this means high rank coals are older, because they have buried longer; however higher rank could also be produced more quickly by compressional forces associated with mountain building or proximity to a heat source such as a volcano.
The major categories of coal in order of progressive diagenesis:
Lignite
Subbituminous Coal
Bituminous Coal
Anthracite
As coal progresses from lignite to anthracite it generally becomes harder, contains less water and less volatiles, becomes blacker and more massive, breaks less readily and becomes a cleaner more efficient fuel.
Lignite moisture content
30 - 60%
Subbituminous moisture content
10 - 45%
Bituminous moisture content
5 - 15%
Anthracite moisutre content
~5%
Lignite volatile matter, fixed carbon content and heat value
25-30%; 25-35%; 4000 - 8300 BTU
Subbituminous volatile matter, fixed carbon content and heat value
30-40%; 35-45%; 8500 - 12,000 BTU
Bituminous volatile matter, fixed carbon content and heat value
20-40%; 45-86%; 12,000 - 15,000 BTU
Anthracite volatile matter, fixed carbon content and heat value
~5%; 86-98%; 13,000 - 15,000 BTU
BTU
British thermal unit or the amount of heat needed to raise one pound of water one degree Fahrenheit
Fixed Carbon Content
is the solid combustible material left after the ash, volatiles and moisture have been removed. The composition of the organic fraction (carbon, hydrogen, oxygen, nitrogen and sulfur) is determined by an ultimate analysis.
Coal Grade
Measure of the impurities and ash which impacts its suitability for a particular purpose. Coal grade is not used in making resource estimates.
Organic compounds in coal contain what major elements?
Carbon, hydrogen, oxygen, nitrogen and sulfur. Up to 76 other naturally occurring elements in minor and trace amounts are also in coal, including quartz, kaolinite, illite, montmorillonite, chlorite, pyrite, calcite and siderite.
What minerals will foul (or slag) the coal furnace?
phosphorus or the sodium in montmorillonite which will form deposits inside the furnace that reduce its efficiency or render it inoperable until it is cleaned, while illite for example would not foul the furnace.
What impacts the design of a coal furnace?
Melting temperature of the ash. Coals with iron-bearing pyrite or siderite have a low temperature melting point and the ash collects at the bottom of the furnace (bottom ash). Coals that contain aluminum such as from kaolinite or illite have relatively high fusion temperatures and create fly ash that is blown through the furnace with the gas and require a different furnace design. Once a furnace is designed to burn one type of coal it has to continue to burn the same type of coal or be completely redesigned.
What happens when the pyrite in coal is burned?
The iron combines with oxygen and is burned but the sulfur is released as sulfur dioxide or SOx.
Pyrite Chemical formula
FeS2
Consequences of burning coal minerals
SOx combines with moisture in the air and forms sulfuric acid which is responsible for acid rain.
Mercury and selenium may also be released as gas when coal is burned. Mercury is considered a HAP by the EPA and coal-fired powerplants are the largest source of mercury emissions in the U.S.
Arsenic is present in most coals and is being studied for its potential to be toxic in groundwater if it is leached from mining waste or fly ash.
Coal Ash Disposal Rule of 2015
The CCRs are considered solid waste, and surface impoundments are to be managed under subtitle D of RCRA.
CCR
Coal Combustion Residuals
How does Circular 891 define coal resources?
As the in-lace tonnage estimates of Identified and Undiscovered coal deposits, utilizing a specific thickness. Coal reserves are the economically extractable part of the resources at the time of classification, after considering environmental, legal and technological constraints. The market value has to be greater than the total cost to extract the coal.
What is required for a coal deposit to be classified as an Identified Resource?
Coal deposits must be reliably and accurately mapped, of a specified thickness based upon rank, and shallower than 6000 feet.
In the U.S. coal beds containing more than how much ash are not included in resource calculations?
33%
Anthracite or bituminous Coal Depth and Minimum Thickness Resource Definition
< 6000 Feet deep and >= 14 inches
Anthracite or bituminous Coal Depth and Minimum Thickness Reserve Definition
<= 1000 feet and >=28 inches
Subbituminous and lignite depth and minimum thickness resource definition
<= 6000 feet and >= 30 inches
subbituminous depth and minimum thickness reserve definition
<= 1000 feet and >= 60 inches
lignite depth and minimum thickness reserve definition
<= 500 feet and >= 60 inches
In-place tonnage of coal resources can be approximated by using what formula?
tonnage of coal = A x t x w
A = area underlain by coal (acres or hectares)
t = weighted average thickness of coal (inches, feet, centimeters, or meters)
w = weight of coal per unit volume (short or metric tons)
Recoverable Resources
If the recoverable coal resources are cheaper to mine than the market value, then what falls into the category is Reserves.
Why should the reserve date be stated?
Because the economic conditions may change, making reserves Subeconomic Resources if the price of coal drops. Conversely, a rise in the price of coal or removal of a restriction could move a Subeconomic Resource into the reserve category. This economic fluidity is why the term Reserve Base is used. The Reserve Base encompasses Economic, Marginally Economic, and some of the Subeconomic Resource category.
CARS
Coal availability and resource studies
Coal availability and resource studies (CARS)
are used to determine estimates of economically recoverable coal resources.
Recovery of coal
mining in-situ deposits ranges from 30 to 90 percent. Surface mining methods (strip mining) produce the highest recoveries. The stripping ratio is an important economic consideration.. It is estimated by the ratio of the overburden to the coal thickness. The smaller the ratio the greater the cost savings.
Five major regions of coal in the U.S.
- Northern Central Appalachians - Mountaintop removal mining and longwall mining
- Illinois Basin, Central U.S. - Room and pillar mining
- Rocky Mountain and Colorado Plateau - Dragline stripping and strip by tuck-shovel
- Northern Rock Mountains and Northern Great Plains - Strip Mining operations using dragline and truck shovel stripping.
- Gulf Coast - Stripped by dragline or truck-shovel operations.
Coalbed Methane
during the coalification process, methane gas is generated and stored within coal beds. At shallow depths the gas can be produced from open fractures in the coal but at deeper depths the fractures close and reduce the ability of the gas to be recovered.
How is coalbed methane mined?
Commonly the water in the coal traps the gas and must be pumped out to lower the pressure to allow the gas to flow and be recovered. This produced water is often saline and occurs in large volumes and must be disposed of safely. The main dissolved ion components in the water are sodium, bicarbonate, and chloride. Sulfide rather than sulfate is removed as a gas or precipitate.
CBM Water
Good quality water may be reused as potable water, in wetlands or for irrigation. Poorer quality water must be treated, discharged to the surface, or injected underground. If the treatment cost is excessive it may preclude development.
Surface mining
involves the removal of overburden to reach the ores or coal located at a shallwo depth.
Stripping Ratio
is the ratio between the volume of overburden (waste rock) to be stripped to the volume of ore. A high stripping ratio may not be minable for a low grade ore, but could be for a high grade ore.
= volume of overburden / volume of ore
Dry surficial mining methods
include quarrying, open-pit mining, and strip mining.
Primary type of mining for metallic ores in the U.S.
Open pit mines
Open pit mines
Formed by drilling and blasting of hard rocks to recover the ores and remove waste. Benches are cut to excavate the hole. Open pits can become very large.
Area or strip mining.
used for shallow, bedded deposits such as coal. Large dragline shovels remove the overburden and truck-shovels and front-end loaders excavate and remove the coal. AS the dragline shovels dig a deeper pit, the walls becomme steeper and form a highwall which is mined by other methods.
Contour Mines
Cut benches in hilly areas at the level of the coal, remove the overburden to a stockpile and expose the coal seam for mining. As the bed is removed the overburden is replaced.
Auger Mines
Drilled horizontally into the hillside from the benches created from contour mining or from the highwall when it is vertical. The auger is 6-feet in diameter and works best when the coal beds are horizontal.
A highwall miner
is used when the coal beds are dipping. The machine is laser-guided and excavates a rectangular hole with a continuous miner head up to 1200 feet into the coal outcrop.
Mountaintop removal
strips off the overburden from the top of the mountain and fills the adjacent valley with the waste rock. This method disrupts drainages and ecosystems, leaving a plateau.
Placer ore deposits
Are worked either by wet or dry surface mining methods. Wet methods include dredges and hydraulic mining , where high water pressures are applied with monitors to materials to break them up and wash them into the sluices. Hydraulic mining was used extensively in the California gold rush but stopped because of its environmental destructiveness
Nitrification
With enough oxygen present, the conversion of ammonium nitrogen to nitrite and then nitrate through bacterial action
Nitrate Mitigation
Biological denitrification, with aid of anoxic bacteria, when there is carbon or sulfur available, nitrate is converted to gas. most effective in silts and clays or layered fine and coarse-grained soils.
Platinum Group Minerals
platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os) and iridium (Ir)
Soft rock underground mining methods
Room and Pilar
Longwall mining
Underground Hard Rock Mining Methods
Stoping and Block caving
Room and Pilar Mining Method
In horizontal deposits the ore is mined out in large rooms where pillars of the ore are left to support the overlying rock. Sometimes if the rock is strong enough the miners then mine out the pillars and let the opening progressively collapse behind them as they withdraw from the mine.
Longwall mining
An enormous machine that shears away at the headwall of the opening and transfers the ore along a conveyor belt to remove it. The overlying material is then left to collapse after the ore is recommend.
Stoping
Means creating underground openings by mining, but generally refers to excavations following steeply inclined or vertical veins. This is often done using drill and blast techniques and constructing supporting structures like square sets.
Block Caving
A large weak, fractured, or friable ore body with disseminated ore is blasted to break the ore up and then the ore is removed through the undercutting process from the bottom while the rock above continues to cave providing a continuous stream of ore to be removed.
Underground mining methods for coal?
Either room and pillar or longwall mining.
Limiting depths for room and pillar mining?
approximately 3000 feet for coal mines because of rock bursts, floor upheaval, gas emissions and potential for explosive dust.
Why isn’t shortwall mining used that frequently?
Because it uses shuttle cars to remove the coal which are not as productive as conveyors.
Advantage of longwall mining?
the ore can be completely extracted, the roof rock can be almost completely caved and surface subsidence is very uniform.
Stopes
Underground openings from which ore is extracted
Open stoping
used in steeply dipping vein in strong rocks. No ground support is used. Stopes are left as permanent openings.
Sublevel open stoping
Used to mine strong ores with strong walls. Large blocks of ore are partitioned between the main levels and drilled and blasted so that the sublevel retreats more than the layer above. This removes bottom support and allows the ore to fall directly to the floor of the stope.
Longhole open stoping
is accomplished by a fan-shaped drilling pattern and massive blasting. It requires fewer personnel and is used for large blocks of relatively uniform ore. Care must be taken to leave the wall rock intact, but still blast all the minable ore. Broken ore is extracted from a draw point at a lower level.
Shrinkage stoping
Is best suited to veins and beds dipping 60 degrees or more that are strong enough to stand unsupported. The method relies on the accumulation of broken ore to temporarily support the walls. Ore is broken by blasting above; it then swells in volume. The stope is generally left empty after the ore has been completely withdrawn.
Stull stoping
a form of open stoping in which timbers (stulls) are wedged between the hanging wall and footwall. Walls must be fairly competent to be supported by the timbers while the ore is mined.
Cut-and-fill stoping
is used in steeply dipping competent ore veins with weak walls. It is an important mining method for wide vein deposits. Ten-foot veins at depths of 3250 feet have been mined using this method. Waste material is used to permanently fill the stope as the ore is worked.
Square-set stoping
interlocking timber sets are emplaced as each block of ore is removed, and waste rock is dumped into completely timbered areas. The interlocking timbers provide good support in poor ground conditions.
Top slicing mines
Thick deposits with weak ore and weak walls. A mat of timbers is place don the floor of each horizontal cut and the overlying material caves onto it. Almost 100% of the ores can be removed but the method is labor intensive and requires a source of timber.
Block caving and sublevel caving
Approporate for bodies of weak ore with relatively weak wall rock or wall rock that may be weakened by selective blasting. Blcok caving has a low cost per ton of ore extraction but mining is not sleective. so the ore is diluted with waste rock and pre-extraction work is extensive.
Ore must be closely jointed or fractured.
Sublevel caving
method of stoping in which sublevels are developed at vertical intervals. Ore is blasted down. The walls are weak and allowed to collapse onto the ore. Even though the ore becomes diluted with waste rock , the extrication rate is high.
Heap leaching
Commonly used for low-grade gold ore. Rocks are crushed and spread out on a pad. A cyanide solution is applied which dissolves the gold into a pregnant solution absorbed onto activated carbon pads and recovered.
Vat leaching containerizes the ore.
Froth flotation
separates the ore from the gangue by creating a froth upon which the minerals separate out. The advantage of this method is that multiple ores can be separated out using specifical chemical reactions.
Used when gold is associated with sulfide minerals.
Coal Cleaning
Removes impurities like sulfur, ash, and rock. Coal is separated from the impurities using density differences.
What does acid mine drainage occur from?
Mining coal containing pyrite or metallic sulfide ores.
What is a way to remediate acid drainage?
Active treatment using lime and settling or passive treatment using anoxic limestone drains.
What is a way to remediate metal contamination in water?
Treat waters and soils with compounds that will bind with the metals to precipitate out.
What is a way to remediate sedimentation and erosion?
Implement soil erosion control.
What is a way to remediate cyanide?
Reclamation utilizing detoxification processes particularly with iron compounds that can bind up the cyanide making it less toxic.
What is a way to remediate Emissions?
Can be collected through air pollution controls on the smokestacks at the smelters or by stabilizing and reclaiming tailing ponds and piles
Capping and Surface reclamation mine remediation method
-Does not reduce volume or toxicity of waste.
-Settlement, subsidence, freeze-thaw, or desiccation may cause fractures in the cap allowing surface water infiltration.
-Uses conventional construction methods and can be completed in a timely fashion
-relatively inexpensive but may involve long-term monitoring and maintanence.
Collection, Diversion, and Containment
- Does not reduce volume or toxicity of waste
- Rainfall or flooding could negatively affect effectiveness
- generally relatively inexpensive to implement depending on site-specific conditions
Extraction & Removal
- Risk of recontamination of other areas of site
- May require large-scale earth-moving equipment
- Requires dust suppression operations
- Distance to disposal site must be considered
- May be cost prohibitive.
Chemical Precipitation Treatment Method
Introduce a precipitating agent to promote chemical precipitation of the metals
Clarification treatment method
Settlement of the suspended particles (solids) and coagulated pollutants
Chemical Oxidation Treatment Methods
Introduction of oxidizing agents such as hydrogen peroxide, potassium permanganate, persulfate, or ozone to destroy organic contaminants. may be able to be implemented in-situ or ex-situ
Neutralization Treatment method
the introduction of a reagent to adjust the pH
Vitrification Treatment Method
An electrical current is introduced through a series of electrodes that have been installed in the ground. The heat created melts the soil and converts it into a glass-like material that solidifies and immobilizes the waste.
Distillation Treatment Method
Soils contaminated with volatile organics are heated in a vacuum to volatilize the contaminants. The vapors removed through he vacuum process are then cooled, condensing the contaminants.
Cyclonic Separation Treatment Method
Particulate matter is removed through the use of a vortex which allows the particulate matter to drop out.
Solidification treatment method
a process which creates a solid block out of waste materials, usually utilizing a cementation process
Stabilization treatment method
incorporates changing the chemicals present to a less harmful or less mobile phase
Encapsulation Treatment method
Stabilization or solidification treatment. These methods do not destroy the chemical they just encapsulate them to keep them from moving into the surrounding environment.
Petroleum
An extremely complex mixture of hydrocarbon compounds with minor amounts of nitrogen, oxygen and sulphyr as impurities.
Petroleum gas (natural gas)
consists of the lighter paraffin hydrocarbons, of which the most abundant is methane gas.
Examples of surficial petroleum deposits
seepages, springs, exudations of bitumen, mud volcanoes, vug and vein fillings, inspissated deposits, and various kinds of oil, kerogen and bituminous shales.
petroleum provinence
a region in which a number of oil and gas pools and fields occur in a similar or related geologic environment.
Reservoir Rock
The porous and permeable body of rock, most often sandstone and carbonate.
Trap
enclosure barring movement of petroleum
GOC
Gas oil contact
OWC
Oil water contact
GWC
Gas water contact
Cracking or catagenesis
process where kerogen breaks down into shorter chain molecules - oxygen decreases, carbon content increases with the increased temperature.
Algae in deep anoxic lakes forms…?
way (paraffin) crude oils or liquid hydrocarbons
Marine plankton and bacteria (anoxic) forms…?
oil and some gas
Terrestrial plants (oxic to sub-oxic) forms…?
coal, light oil and gas
What are typical porosity values of reservoir rock?
5% to 30% and most commonly are in the range of 10 to 20%
Styolites
teethlike interlocking projections at a contact in carbonate rocks that often form a vertical permeability barrier to petroleum migration.
Structural Traps
Formed by post-depositional deformation. They may be folds, faults, or domes.
Secondary stratigraphic traps
include unconformities and diagenetic traps formed by the creation of secondary porosity by replacement, solution, or fracturing
Hydrodynamic Traps
A fluid potential gradient exists in an aquifer such that the flow of water is directed downdip, the hydrodynamic force may bar the up-dip movement of any petroleum in the aquifer, even though the petroleum is more buoyant than the water. Relatively rare.
Combination Trap
formed by two or three, or more geologic episodes. Neither the stratigraphic nor structural aspects of the trap are dominate. A special type of combination trap is the diapir.
Diapirs/Domes
produced by the upward movement of less dense sediments. They are usually salt or overpressured clays. Salt domes are common in the U.S. Gulf Coast. In order to explore diapirs, high quality seismic data are needed. If data are available, closures on which to site exploration wells can be identified.
PRMS
Petroleum Resources Management System - Classification system based upon whether there is a chance of commercial development of oil or gas versus the range of uncertainty of quantities associated with the deposit.
Total Petroleum Initially-In-Place
There are four recoverable resource classes of increasing commerciality
- Prospective Resources
- Contingent Resources
- Reserves
- Production
These four classes comprise the PIIP.
PIIP
Total Petroleum Initially-In-Place
Contingent Resources
quantities of oil and gas to be potentially recoverable. There are technological, environmental, or business hurdles that need to be overcome before they can become reserves. To be classified as contingent, there must be evidence of intention to proceed with development within a typical 5-year time frame.
Production
The cumulative quantity of oil and natural gas already recovered.
Prospective Resources
undiscovered hydrocarbons whose volumes are estimated and are partially recoverable.
Unrecoverable resources
it is non-producible at the current time. ITs status may change as technology or commercial circumstances change to allow it to be recovered in the future.
In the U.S., how are oil reserves calculated?
volumetrically and not by weight or density.
What does the calculation for proven oil reserves consists of?
- Determining the volume of the reservoir rock
- Finding what percent of that volume is filled with oil
- Evaluating the amount of oil that is recoverable
What is the irreducible water saturation value calculated from?
Archie’s law
Archie’s Law
Relates to the downhole electrical resistivity of a shale-free sandstone to the hydrocarbon saturation in the pore spaces.
Based on the fact that rock is nonconductive and the fluids other than water are nonconductive.
Factors taken into consideration: cementation, saturation exponent, tortuosity
Tortuosity Factor
variation in grain sies, compaction of the grains and thus the pore structure
GOR
Gas to oil ratio
What is the recovery factor for heavy oil?
About 10 - 15% for heavy oil, with a maximum of 35%
Primary Recovery
the natural depletion of the reservoir which is about 20%
Secondary Recovery
Additional recovery generated by the introduction of fluids or through pressure maintenance, ranges between 15-25%
EOR
Enhanced oil recovery or tertiary recovery, uses thermal methods, gas injection or chemical flooding to increase recovery.
GOR impacts on recovery
if the GOR is high, the oil will shrink when it is brought to the surface because the gas content will bubble off. The shrinkage factor converts the volume of oil measured in the reservoir to the volume of stock-tank oil measured at the surface and is expressed as a decimal fraction less than one.
STO
stock-tank oil
How is the STO calcualted?
Temperature, pressure, and GOR of the oil, at a standard temperature of 60 F.
Recoverable STO = Area x thickness x porosity x oil saturation x recovery factor / Formation volume factor
How to convert STO to U.S. gallons
divide STO by 5.615
1 barrel equals how many gallons
42 gallons
Measured Depth (MD)
Measured along the borehole which deviates from the vertical
TVD
True vertical depth
Second largest energy source consumed in the U.S.
Natural gas, just behind petroleum. Shale gas accounted or about 3/4 of the total U.S. natural gas production. Top five producing states: Texas, Pennsylvania, Oklahoma, Louisiana and Ohio
Natural gas is produced from what different types of occurences?
Conventional gas fields
gas associated with conventional oil fields
shale gas
tight gas
coal-bed methane gas
When are shales too viscous to stimulate through fracking?
when they contain between 45-65 clay%
A-Line
The line of the plasticity chart that divides clays from silts.
Equation of the line is horizontal at PI =4 to LL = 25.5, then PI =0.73 (LL - 20)
Atterberg Limits
Water content at the boundaries between the states of consistency of a soil.
Bearing Capacity
The load per unit area which the ground can safely support without excessive yield.
Bulk Density (p)
The density of a material measured in mass per unit volume.
Bulk Modulus (K) or Incompressibility Modulus
A modulus of elasticity which relates a change in volume to the hydrostatic state of stress. It is the reciprocal of compressibility.
Coefficient of Curvature (Cc)
A measure of the curvature of the grain size distribution plot. Well-graded sands and gravels have coefficients of curvature between 1 and 3.
Coefficient of Uniformity (Cu)
A measure of the grain size uniformity using the ratio of particle sizes D60 to D10
Compaction
The process of increasing the density of a soil (usually fill) by rolling, tamping, vibrating or other mechanical means.
Consistency
The degree of adhesion between soil particles that can resist deformation or rupture.
Consolidation
Gradual or slow reduction in volume and increase in density of a soil mass in response to increased load or compressive stress.
Critical Void Ratio
The final void ratio at ultimate strength achieved by loose and dense samples of the same soil after shearing
Degree of Saturation (SR)
The ratio of the volume of water to the total volume of void space3. The value of SR can range from zero for a completely dry soil to one ( or 100%) for a fully saturated soil.
Dilatancy
An increase in the bulk volume during deformation, caused by a change from a close-packed structure to an open-packed structure.
Direct Shear TEst
A laboratory test to measure the shear strength of a soil.
Dry Density (Pd)
The density of soil when it is completely dry;
bulk density divided by 1 + water content.
Dry Strength
The strength of a soil when dry as determined by the crushing test
Effective Size (D10)
The diameter D10 which corresponds to the percentage, by weight, of grains equal to 10% on the grain-size diagram. Ten percent of the particles are finer and 90% are coarser than the effective size.
Effective Stress
The part of the total stress that is due entirely to the solid particles of the soil, and represents an excess over the neutral stress or pore-water pressure.
Effective stress = total stress - pore water pressure
Gap-graded
A soil in which some particle sizes are missing. Also called skip-graded.
Gradation Curve
A graphic representation of the results of a sieve analysis plotted as percent passing vs. grain size
Hooke’s law
A statement of elastic deformation - the strain is linearly proportional to the applied stress.
Liquid Limit (LL)
The upper limit of the plastic state. Water content, in percent of dry weight, at which two sections of a pat of soil, separated by a specified distance, barely touch each other but do not flow together when given a sharp blow.
Mohr Circle
Graphical representation of the state of stress (normal and shear) on a particular plane inclined at an angle to the major principal stress.
Mohr-Coulomb Equation
An equation describing the failure of a material in shear fracture. The rupture line in a Mohr circle can be approximated by this equation.
Normal Stress
The component of stress that acts perpendicular to the plane.
Optimum Moisture content
The moisture content at which the maximum dry density of a soil is attained.
Piping
Erosion by percolating waters or seepage in a layer of subsoil resulting in caving and the formation of tunnels or pipes through which the soluble or granular material is removed.
Plastic Limit (PL)
The lower limit of the plastic state. Water content at which the soil begins to crumble when rolled out into thin threads.
Plasticity Index (PI)
Range in water content between the liquid limit (LL) and the plastic limit (PL).
PI = LL-PL
Poisson’s Ratio
An elastic constant (does not exceed 0.5). The ratio of the lateral unit strain to the longitudinal unit strain in a body that has been stressed longitudinally within its elastic limit.
Poorly Graded
A soil with most grain sizes present in one size range. Equivalent to the geologist term “well sorted”
Quick Condition
The condition of soil in which a decrease in intergranular pressure allows water to flow upward with sufficient velocity ot reduce significantly the soil’s bearing capacity.
Relative Density
The ratio of the difference between the void ratio of a cohesionless soil in the loosest state and any given void ratio to the difference between its void ratios in the loosest and in the densest states.
Relative Compaction
The amount of compaction relative to the moisture-density curve, or compaction curve.
Seepage
The movement of water or other fluid through a porous material such as soil.
Settlement
The gradual downward movement of an engineered structure due to compression of the soil below the foundation.
Shear Modulus (G) or Rigidity Modulus
A modulus of elasticity in shear. It measures the shear strain resulting from shear stress on a plane.
Shear Strength
The internal resistance of a soil to shear stress consisting of a combination of friction and cohesion. An important property relating to the ability of the soil to support itself or support a load imposed upon it.9475
Shear Stress
The component of stress that acts along a plane through any point in the body.
Shrinkage Limit
water content at which the soil volume is lowest.
Smectites
A group of clay minerals that expand when they absorb large quantities of water.
Specific Gravity
The ratio of the density of the solid particles to the density of water at 4 C
Strain
Change in the shape or volume of a body as a result of stress, defined as the ratio of the change to the original shape.
Stress
The force per unit area.
Toughness
The property of a soil that is able to absorb stress by plastic deformation.
Triaxial Test
The most widely used shear strength test in which the drainage conditions can be controlled. Three principal types of tests are:
unconsolidated-undrained (UU)
consolidated-undrained (CU)
consolidated-drained (CD)
U-Line
The line on the plasticity chart that marks the approximate upper limit of the relationship between the plasticity index and the liquid limit for natural soils. It is a check against erroneous data - if a data point plots above or to the left of the line, verify the information.
Unconfined Compressive Strength Test
A special case of the triaxial test in which axial stress is applied to a specimen under atmospheric pressure to obtain the value of the shear strength.
Uniformity Coefficient (Cu)
The ratio of the D60 size to D10 size.
Unit Weight (y)
The weight of soil plus water per unit volume
Void ratio (e)
The ratio of the volume of void space to the volume of solids
Well-graded
A soil with all grain sizes present with no excess in any size range. Equivalent to the geologist’s term “poorly sorted”
Young’s Modulus (E) or Modulus of Elasticity
An elastic constant given by the ratio of stress to its corresponding strain under given conditions of load, for materials that deform elastically according to Hooke’s Law.
Bulk Density Equation
total mass / total volume
Void Ratio Equation
volume of voids / volume of the solids
Porosity equation
Void Volume / Total Volume x 100
Dry Density Equation
= bulk density / water content + 1
Density of water
1000 kg/m^3 at 4 C
Units of bulk density
kilograms per cubic meter or grams per cubic centimeter
unit weight equation
weight of the soil + water per unit of volume
Units of unit weight
pounds per cubic foot. The unit weight of water is 62.4 lbs / cubic feet at 4 C
Where is the coarse-grained and fine-grained soil boundary placed?
At the No. 200 sieve (0.003 inch). The smallest particle visible to the unaided eye.
How to determine coarse-grained vs fine-grained?
If more than 50% is retained by the No. 200 sieve it is coarse grained.
How to determine difference between coarse-grained soils?
Depends on whether more of less than 50% of the grains are retained on a No. 4 sieve
What sized particles (inches) are retained on a No. 4 sieve?
> 3/16 inch
What sized particles are retained on the No. 200 sieve?
> 3/1000 inch
What are coarse grained soils?
either gravels or sands
USCS Boulder Classification
Over 305 mm
USCS Cobble Classification
305 to 75 mm
USCS Coarse Gravel Classification
< 3” to 3/4” sieve or <75 to 19 mm
USCS Fine Gravel Classification
< 3/4 “ to No. 4 Sieve or < 19 to 4.76 mm
USCS Sand Coarse Classification
< No. 4 to No. 10 Sieve or < 4.76 to 1.68 mm
USCS Sand Medium Classification
< No. 10 to No. 40 Sieve or <1.68 to 0.42 mm
USCS Sand Fine Classification
< No. 40 to No. 200 Sieve or <0.42 to 0.074 mm
Well Graded Uniformity and Curvature Coefficient Grades
Cu > 4 for gravel and > 6 for sand; Cc is between 1 and 3
Poorly Graded Uniformity and Curvature Coefficient Grades
Cu < 4 for gravel and < 6 for sand; Cc not between 1 and 3
Skip graded or gap graded material
an absence of one or more intermediate sizes
Atterberg Limits Test
Test for liquid limit, plastic limit and plasticity index of soil
Hydrometer Test
Test for particle-size distribution (Gradation) of Fine-Grained Soils to determine the silt and clay portion
What is the consistency of a soil?
The degree of adhesion between the particles that can resist deformation or rupture. By increasing or decreasing the water content, the consistency can be changed.
Atterberg limit states
solid state when dry, through the semisolid, plastic and liquid states as water is added.
Shrinkage Limit (SL)
Boundary between the solid and semisolid state
Plastic Limit (PL)
Boundary between the semisolid and plastic states
Liquid Limit (LL)
Boundary between the plastic and liquid state
What PI and LL has a high swelling potential?
PI>30 and LL>50
Kaolinite Group and Swelling potential?
Formed through decomposition of orthoclase feldspar (granites), acid rocks in acidic conditions; used for making china. Low swelling potential.
Illite Group and swelling potential?
Formed through the decomposition of micas and feldspars in alkaline conditions, they have a structure similar to muscovite; high Al and K concentrations; the dominant form of clay found mostly in marine clays and shales.
Low swelling potential because interlayer cations of K, Ca, or Mg don’t allow water to enter.
Smectite Group and swelling potential?
Formed thorough he alteration of Ca- and Mg-rich (K deficiency) mafic igneous rocks (basic or volcanic rocks), alkaline conditions; smectites can have up to a 30% volume change; used for drilling muds and for sealing leaky formations but are problematic in slopes and tunnels.
High swelling potential, the interlayer allows water to enter causing swelling based on the amount of water present.
Vermiculites Group and swelling potential?
Formed through the weathering of micas (biotite) or volcanics (chlorite/hornblende); used to absorb spills in industrial and automotive facilities and in agricultural plantings to retain water.
Moderate swelling potential - hydrates similar to smectites but not as responsive due to the high charge of the ionic bonds.
Stress Equation
= Force applied / surface area
Sphalerite
Zinc Ore
Cassiterite
Tin Ore
Galena
Lead Ore
O16
Gets trapped in ice sheets
What does a slug test measure?
Localized values of permeability
Diffusion
Moves from high level of concentration to low level
Dispersion
groundwater flowing through different sized pores at different rates along flow paths and perpendicular to flow paths
Krotovia
Filled animal burrow
Trilobites
Marine animals that lived from the Cambrian through the Permian
Sublittoral
ocean just belwo the littoral or intertidal zone
abyssal
very deep ocean below light penetration
Pelagic
within the column of water of the ocean
regolith
all loose weathered material above bedrock
how does high uniaxial strength impact TBMs
slows penetration
Invert Struts
a compression strut to support the tunnel ribs to resist the pressure from the squeezing ground
Shear modulus
ratio of shear stress to shear strain
modulus of compressive strength
ratio of applied stress to resulting strain being compressed
modulus of elasticity
ratio of tensile stress to tensile strain
Young’s modulus
another name for modulus of elasticiy
Poisson’s ratio
ratio of lateral strain to longitudinal strain within the elastic limit.
Point load tests
lab test to empirically obtain uniaxial compressive strength
Blanket Drain
drainage structure used to accommodate seepage zones on the road cut
particulate matter
airborne contaminates
Focal mechanism solution
shows the direction of ground motion from arrival of a P wave
free product
any petroleum contamination that exists as a separate material that does not mix with or dissolve in water. Because petroleum is lighter than water, free product is usually floating on top of groundwater.
Olistostromes
submarine landslides
Wilson Cycle
describes the important stages in the breakup of continents, subsequent formation of ocean basins, later development of subduction zones and eventual continental collision
A tonne
1,000 kg or 1 million grams grams/tonne and parts per million are equivalent ratios.
Reidel Fractures
Small faults striking at an angle to the main fault movement within the fault zone
Called R Shears
Are used to determine the slip direction along a fault.
In what environment do feldspars form kaolinite?
humid tropical environments
In what environment do feldspars form montmorillonite
humid temperate environments
infiltrometer
measures the rate of water infiltration into soil
thermocouple psychrometers
measures the in situ water potential of plants
stannite
tin ore
how is bentonite formed
alteration of volcanic ash
what type of faulting is most likely to lead to a tsunami
Reverse
