Lab 6 Flashcards
Clastic Sedimentary Rock
Sedimentary rock that forms when physical fragments of preexisting rocks (clasts) are compacted or cemented together.
Physical Weathering
The mechanical breakdown of rocks and minerals
Chemical Weathering
The process that breaks down rock through chemical changes (which chemically decompose the rock)
Weathering
The initial break down of rocks by chemical and physical processes into sediments
Erosion
Removal of the products of weathering (sediment) by wind, water and/or gravity from their site of origin
Transportation
Long-distance movement of sediments mostly by water, but also by wind or glaciers
Burial
The process by which sediments are buried due to the deposition of later sediments
Deposition
Process by which chemical and/or physical sediment precipitate or settle out of water/wind/glaciers
Diagenesis
The physical and chemical changes occurring during the conversion of sediment to sedimentary rock (compaction and cementation) due to increased temperature and pressure. Also known as lithification
Lithification
The process that converts sediments into solid rock by compaction or cementation. Also known as diagenesis
6 steps that create sedimentary rocks (in order)
Weathering
Erosion
Transportation
Deposition
Burial
Lithification (diagnesis)
Chemical Sedimentary Rocks
Sedimentary rock consisting of material that was precipitated from water by either inorganic or organic means
Evaporite
A sedimentary rock formed of material precipitated from solution as water evaporates
Biological Sedimentary Rocks
A sedimentary rock that forms from the remains of organisms
(Bio)chemical Sedimentary Rocks
Sedimentary rock formed in one of two ways
1. Dissolved minerals precipitate out of water (when the water becomes over-saturated in a specific mineral)
2. Sedimentary rock formed from sediments derived from biological processes
Limestone
(Bio)chemical sedimentary rock, composed mainly of calcium carbonate or dolomite, the most common biochemical sedimentary rock. Reacts with HCl (hydrochloric acid).
Coal
A combustible black or dark brown sedimentary rock consisting mainly of carbonized plant matter, found mainly in underground deposits and widely used as fuel.
What happens to physical clasts as they are transported?
Two things happen to physical sediments as they are transported.
1. They change shape due to abrasion (they become smaller and more rounded)
2. They become well-sorted.
Three types of sedimentary environments are
Continental (terrestrial)
Shoreline (transitional)
Marine
Sedimentary Environments
Place where a sedimentary rock is formed, really what it means is where the sediments are deposited, then buried, and finally lithified
Where does limestone form?
Reef environments (far out on the continental shelf in tropical areas)
Where does sandstone form?
On the beach
Where does mudstone form?
Abyssal place
Where do the evaporites gypsum and halite form?
In a desert lake environment where there is lots of evaporation
Which weathers faster, quartz or feldspar?
Quartz is very resistant to weathering, feldspar is not. Feldspar weather faster
Where does conglomerate form?
Conglomerates form in mountain steam or at the base of cliff along a seashore
How do we recognize sea level rise transgression) in the rock record?
As sea level rises, deeper water sediments are deposited on top of shallow water sediments. In the rock record we would see finer grained sedimentary rocks (deep water sediments) deposited on top of coarser sediments (shallow water sediments).
How do we recognize regression (sea level fall) in the rock record
As sea level falls, shallow water sediments are deposited on top of deep water sediments. In the rock record we would see coarser grained sedimentary rocks (shallow water sediments) deposited on top of finer sediments (deep water sediments).
What type of sedimentary rock react with acid?
Carbonates (example: limestone)
Examples of clastic sedimentary rocks
Conglomerate
Breccia
Sandstone
Siltstone
Mudstone
Shale
Examples of (bio)chemical sedimentary rocks
Limestone
Fossiliferous limestone
Coquina
Chalk
Chert
Where does coal form?
Swamps
Where do we find volcanoes?
Convergent boundaries, hot spots and drivgent boundaries
Basalt is formed at
Divergent boundaries are hot spots
Andesite is formed at
Subduction zones and hot spots
Rhyolite is formed at
Subduction zones and hot spots are
How do we identift different lava flows on Mars and the Moon
Using satellite imagery, we look for flow margins, differences in colors and textures, differences in the number of impact craters
An area on the moon with greater number of impact craters would be _____ than an area with fewer impact craters
older
Why do we not use impact craters to identify flows on Earth?
Due to weathering, plate tectonic processes, vegetation and the large amounts of ocean, impact craters are mostly hidden, destroyed or nonexistant
How do we identify different lava flow on Earth?
- Differences in color and texture
- Flow margins
- Differences in vegetation
- Chemical analysis of the different flows
Shield volcan
A low, flat, gently sloping volcano built from many flows of fluid, low-viscosity basaltic lava
What type of magma is the most common in the universe
Basaltic
Volcanic Hazards
Natural hazards associated with eruptions. Volcanic hazards include:
Lava flows
Lahars
Pyroclastic flows
Ash falls
Landslides
Tsunami
Volcanic Gases
Projectiles
Lava Flow
The spread of lava as it pouts out of a vent
Lahar
A destructive mudflow or debris flow on the slopes of a volcano. Typically contains rock, soil, vegetation and water. and flow down river valleys like fast moving rivers
Pyroclastic flow
Pyroclastic flow is a density driven current formed when an eruption column collapses on itself causing hot ash, lava fragments and gasses to flow rapidly down the flanks of a volcano
Ashfall
Volcanic ash that has fallen through the air from an eruption cloud
Volcanic rockslides
Loose soil, rock, vegetation, volcanic debris slide downhill along the flanks of a volcano
Volcanic gases
Vapor and aerosols that exit a volcano, some of which are dangerous
Volcanic Projectiles
large particles hurled from a volcano
What volcanic hazard is associated with Mount Rainer
Lahar
Metamorphic Rock
A type of rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions (due to the presence of fluids)
What type of rocks can become a metamorphic rock?
All rocks can become metamorphic rocks (igneous, sedimentary and even metamorphic rocks)
What are the two main types of metamorphism?
Regional and contact metamorphism
Regional Metamorphism
A type of metamorphism in which occurs over a large are due to burial and heating associated mountain building and subduction at convergent boundaries.
Contact Metamorphism
Metamorphism that occurs adjacent to igneous intrusions (the high temperatures associated with the igneous intrusion ‘bake’ the surrounding country rocks)M
Metamorphose
A less common type of metamorphism in which a rock’s overall chemical composition changes during metamorphism because of reactions with hot water that bring in or remove elements. Commonly occurs at mid-ocean ridges.
Confining pressure
Stress (pressure) that is applied uniformly in all direction. Occurs at depth.
Directed pressure
Pressure applied in one direction, occurs at convergent margins
What two things need to be present for foliation in metamorphic rocks to occur?
Directed pressure and platy minerals
Foliation or foliated texture
The metamorphic rock texture in which mineral grains are arranged in planes or bands
Granoblastic texture
Metamoprhic texture with no foliation
Protolith (parent rock)
The original rock form which a metamorphic rock formed
Index minerals
Certain metamorphic minerals form at very specific temperatures and pressures. Thus they are an ‘index’ or guide to the depth and pressure of the metamorphic rock’s T and P of formation
Slate
Low- grade foliated metamorphic rock. Grains are not visible. Exhibits slaty cleavage, planes of weakness that allow the rock to easily split into thin layers.
Phylilite
Low grade foliated metamorphic rock that exhibits phyllitic texture (slaty cleavage where the surfaces) Grains are not visible.
Gneiss
Intermediate to high grade foliated metamorphic rock that consists of alternating bands of mafic and felsic minerals (known as gneissic banding)
Schist
Intermediate grade foliated metamorphic rock that exhibits schistosity, a planar orientation of visible mica minerals (biotite and muscovite). Garnet is common.
Hornfel
Granoblastic (non-foliated) fine-grained metamorphic rock formed contact metamorphism of mudstones.
Name the four foliated rocks from lowest to highest grade
Slate
Phyllite
Schist
Gneiss
Quartzite
A metamorphic rock formed by the metamorphism of quartz sandstone. Can be formed by regional or contact metamorphism as quartzite is made up of a single stable mineral (quartz) that is not platy.
Marble
A metamorphic rock formed by the metamorphism of limestone. Can be formed by regional or contact metamorphism as marble is made up of a single stable mineral (calcite) that is not platy
Metamorphic Grade
The degree to which the parent rock changes during metamorphism as pressure and temperature increases. Higher metamorphic grade rocks exhibit more changes in texture and/or mineralogy
What are the two metamorphic textures?
Foliated and granoblastic (non-foliated)
Mass wasting (mass movement)
The downslope movement of material due to gravity
Slope failure
The downslope movement of material on an unstable slope
Unstable slope
Slope that is likely to fail. Also known as a weak slope
Stable slope
slope that is less likely to fail. also know as a strong slope
Unconsolidated material
Sediment that is loose and uncemented
Consolidated material
sediment that is compacted and bound together by mineral cements
Classification of mass wasting events is based on
- Nature of the materials (consolidated vs unconsolidated)
- Type of motion (fall, flow, slide)
- Rate of motion (fast or slow)
Which is more stable on a slope, consolidated or unconsolidated material? Fall
Mass wasting event where the material moving falls or bounces down a cliff face
Type of mass wasting movement: Flow
Moving material has internal motion, like a fluid
Type of mass wasting movement: Slide
Moving material slides down a slope as a unit
Rock avalanche
A larger mass of rock initially breaks off on a steeper slope and travels faster/farther than a rockslide, breaking apart along the way. Similar to a snow avalanche but made of rocks.
Rockslide
Individual large blocks of rock slide down a slope as a unit, often occurring along downward sloping bedding or joints
Rockfall
Vertical or near vertical free fall of rock unit, results in accumulation of talus (slope formed by accumulation of rock debris)
Creep
The slow downhill movement of weathered, unconsolidated rock material. Causes fenceposts to lean and an undulated appearance of soil slopes
Slump
Slow slide of unconsolidated material downhill as a unit for a short distance. Forms a scarp that is generally shaped concave upward, like a spoon.
Earthflow
Slow to moderate velocity flow of relatively fine-grained unconsolidated material that has become saturated with water.
Debris slide
Similar to a slump but bigger and faster
Mudflow
Fast flows of water that contain large amounts of suspended particles and silt, generally runs down a channel. Can have the consistency of wet concrete.
Debris flow
Rapid mass movement of a combination of loose soil, rock, organic matter, air, and water mobilized as a slurry (resemble big muddy rivers). Slopes denuded of vegetation by fire or clearcutting are particularly susceptible to debris flows, especially after sudden intense rainfall.
Debris Avalanche
Very rapid and turbulent mass wasting of debris, air, and water. Behaves like a snow avalanche
Slope stability
The potential of a slope to withstand and undergo movement
Factors affecting slope stability
- Forces: Gravity vs static friction (downslope force vs resisting force)
- Slope material: Unconsolidated vs consolidated
- Water content of slope materials
- Slope gradient
- Vegetation
Gradient
An incline or slope; the rate of incline
The vertical change in a slope over the horizontal distance it occurs over
Factors affecting slope stability: Downslope force vs resisting force
An object on a slope will slide if the downslope force is greater than the resisting force
An object on a slope will not slide if the resisting force is greater than the downslope force
Factors affecting slope stability: Slope material
Which is more stable on a slope, consolidated or unconsolidated material?
Consolidated material
Factors affecting slope stability: Water
There are three piles of unconsolidated sediments: dry, moist and saturated. Put the three in order of increasing slope stability
- Saturated sediments (least stable)
- Dry sediments
- Moist sediments (most stable)
Factors affecting slope stability: Gradient
Which is more stable, a steep slope or a less steep slope?
The less steep slope is more stable
Factors affecting slope stability: vegetation
Vegetation on slopes makes the slopes more stable
Friction (force)
The force that holds together dry sediments
Angle of repose
The steepest angle at which loose material remains stationary without sliding downslope
Geologic cross section
A diagram showing the geologic features that would be visible if vertical slices were made through part of the crust
map view
The view of the Earth’s surface drawn as if you were looking down on an area from above
Block diagram
Cartoon representation of a block of the Earth showing the surface of the Earth (map view) and the two sides (cross-sections)
Strike and dip
The orientation (map direction) and attitude (map direction and angle) of a geologic feature
Strike
The direction of the line formed by the intersection of a fault, bed, or other planar feature and a horizontal plane
Dip
Angle a bed makes as it intersects the surface of the Earth. Oriented at 90 degrees to the strike.
Strike and dip symbol
Map symbol showing the strike and dip of a geologic feature (such as a bed or a fault).
Consists of two intersecting perpendicular lines, the long line is perpendicular to the strike of the bed, the short line shows the direction of dip.
Fold
A bend in layers of rock, due to compressive forces at convergent plate boundaries
Fold axis or hinge line
The line made by the lengthwise intersection of the axial plane with a horizontal suface
Axial Plane
Imaginary plane that divides a fold as symmetrically as possible
Fold limb
Sides or legs of a fold
Syncline
A downward fold in rock formed by compression in Earth’s crust
Identifying characteristics of synclines
Youngest layer in the center
Beds dip down and towards the center fold axis
Anticline
An arched shape fold in rock formed by compression of Earth’s crust
Identifying characteristics of anticlines
Oldest beds are in the center
Beds dip down and away from the center fold axis
Dome
Resemble anticlines, but the beds dip uniformly in all directions away from the center of the structure. Caused by compression
Basin
Resemble syncline, but the beds dip uniformly in all directions towards the center of the structure. Formed by compression
Fault
A crack in the earth’s crust along which there has been movement
Foot wall
The block of rock that lies below the fault plane
Hanging wall
The block of rock that lies above the fault plane
Dip-slip fault
A fault in which the movement is vertical (parallel to the dip of the fault). Reverse and normal faults are dip slip faults
Normal fault
A type of fault where the hanging wall slides downward; caused by tension in the crust
Reverse fault
A type of fault where the hanging wall slides upward; caused by compression in the crust
Strike-slip fault
A type of fault where rocks on either side move past each other sideways along the strike of the fault with little up or down motion, caused by shear stress in the crust
What geologic structures are formed at convergent boundaries?
Folds (anticlines, synclines, domes and basins) and reverse faults
What geologic structures are formed at divergent boundaries?
Normal faults
What geologic structures are formed at transform boundaries?
Strike-slip faults
