Midterm 2- Dynamic Earth Flashcards
Cross section of a stream and velocity
The deepest part of the stream has the highest velocity.
Outer vs inner portion of a meandering stream
Outer parts of meander:
→ velocity is highest
→ erosion
→ cutbank
Inner meander bends :
→ velocity is low
→ deposition
→ point bars
Liquefaction
Loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking. Causes major subsidence, fracturing, and horizontal sliding of the ground surface
Describe the process that causes a nonconformity
Occurs where rocks that formed deep in
Earth are overlain by sedimentary rocks
formed at the Earth’s surface. Indicates that all the rocks overlying the metamorphic or
igneous rocks have been removed by
uplift and erosion.
Hanging valley
formed when the main glaciers cut deeper than side tributaries
Kame
Hills formed by sediment deposition
in/on ice – left after the glacier melts
earthquakes that follow the largest shock of an earthquake sequence
Aftershock
Glacial erosion and deposition
Glaciers move, pick up & transport
rocks and Glaciers transport material and melt
Amplification of seismic waves
Soft sediments amplify seismic vibrations increasing damages
sheets of floating ice attached to land usually occupy coastal embayments
Ice shelves
Surface faulting
Displacement that reaches the Earth’s
surface during slip along a fault.
* Commonly occurs with shallow
earthquakes (epicenter <20 km.)
* May accompany aseismic creep or
natural or man‐induced subsidence
Shallow Earthquakes
Form through tension and normal faulting at divergent boundaries; strike-slip at transform faults
The four wave types
A)Body waves
1)P waves
2)S waves
B)Surface waves
3)Love wave
4)Reighleigh wave
the degree of earthquake shaking at a given locale based on the amount of damage
Intensity
Types of stream deposition features
1)Flood plains
2)Terrances
3)Alluvial fans
4)Deltas
Horizontal fold
is a special type of fold in which both limbs are parallel but offset to each other. The limbs are horizontal, or nearly so.
Ground failure
The term ground failure is a general reference to landslides, liquefaction, lateral spreads, and any other consequence of shaking that affects the stability of the ground.
Graded profile
a smooth concave profile which is steep as the source(high erosion) and gentle at the mouth (high deposition)
Terrances
when streams carve downward into their floodplains, leaving discontinuous remnants of older floodplain surfaces as step-like benches along the sides of the valley
Anatomy of a delta
1)Topset beds- at the very surface of the delta and sit on the foreset beds
2)Foreset beds- sit under the topset bed and form a slope towards the bottomset bed
3)Bottomset beds-lowest bed at the bottom of the body of water, made from the progradation of the foreset bed
Continental glacier
Glaciers much larger than Alpine glaciers that cover entire land masses
Moraine formed as the ridge of till at front of a stable glacier
End moraine
Flashflood
A flood caused by heavy or excessive rainfall in a short period of time
a mountain glacier whose flow is confined by valley walls, forms a U shape
Valley glacier
Plucking
Water seeps into cracks, freezes, and mechanically breaks up the bedrock.
These fragments are plucked out by glacier.Rock fragments dragged
along the base of the glacier.
Fold types
1)Syncline
2)Anitcline
3)Horizontal fold
4)Plunging fold
Describe the process that causes an angular unconformity
1)Sediments are accumulated in a bed
2)Later tectonic forces cause uplifting, folding, and deformation of sedimentary layers during mountain building
3)Erosion strips away the top layers leaving an uneven plain with exposed folded portions
4)Subsidence below the sea allows for new deposits on formerly eroded surface. The surface layer where the new sediments meet preserves an angular unconformity
Two methods to determine age of strata
1)Relative age and dating which places rocks and events in formation sequence
2)Radiometric age specifies the actual number of years that have passed since an event
occurred using radioactive decay
Crevases
Brittle surface fissures that form over lower plastic flow
Strike
measured compass
direction of a line produced
from the intersection of a
horizontal plane with an
inclined rock plane.
Columnar jointing
a geological structure where sets of intersecting closely spaced fractures, referred to as joints, result in the formation of a regular array of polygonal prisms, or columns. often seen in thick lava flows, is a result of cooling and contraction of lava.
Evidence for Continental drift
1)Geographic fit of continents
2)Fossil evidence range overlap
3)Fold belts
4)Glaciations & Palaeoclimates
Phanerozoic Eon
last 570 million years,Pangea fully assembled and results in the Permian
Mass Extinction Event
Turbulent flow
Molecules travel in complex paths
leading to mixing! Can keep
sediment in suspension and Helps erosion
The P-wave shadow
because of the existence of the liquid outer core. When the P-waves enter the liquid core, they are refracted, or bent, away from their original path. This leaves a region where the P-waves do not travel
factors that determine laminar or turbulent flow
1)velocity (rate of movement)
2)geometry (primarily its depth)
3)viscosity (higher viscosity → greater tendency for laminar flow)
the blocks of continental fragments and oceanic islands that have collided with a continent and are now permanently attached
Accreted Terrane margins
Lehmann Discontinuity
The Lehmann discontinuity is an abrupt increase of P-wave and S-wave velocities at the depth of 220 km in Earth’s mantle. P waves slow and S waves dissapear in the liquid outer core. P waves speed up when hitting the solid inner core
relatively smaller earthquakes that precede the largest earthquake in a series
Foreshock
Moraine formed from tributary
glaciers joining
Medial moraine
For each increase in magnitude, the energy released increases ~ 31.6 times
Frequency and magnitude scale
made of sediment that slowly builds up directly underneath a glacier by tiny streams, or as the result of a glacier meeting hills and valleys in the natural landscape, left as a remnant of a retreating glacier
Ground moraine
Stratigraphic Superposition
In any undisturbed stratigraphic sequence, the oldest layers are at the bottom of the sequence, and the youngest units are at the top
a glacier, a thick layer of ice and snow, that covers fewer than 50,000 square kilometers
Ice caps
Horn
Peak that forms when 3 or more cirques meet, forms a distinct triangular shape
Epicenter
point on Earth’s surface directly above the focus
Developed using California buildings as its standard Rates from I (not felt) to XII (total damage)
Modified Mercalli Intensity Scale
a planar zone of seismicity corresponding with the down-going slab in a subduction zone
Wadati-Benioff Zone
Braided stream
Highly variable discharge and flow
volume. Lots of sediment in stream,
Flows around islands & bars
formed when a glacier cuts a U-shaped valley by ice segregation and abrasion of the surrounding bedrock forming
steep-sided inlets to sea
Fjord glacier
Till
unsorted random mix of rocks deposited by glaciers that are
10-100’s m thick – “rock flour”
Structure of geologic time from largest to smallest
1)Eon→ large period of time
2)Era
3)Period
4)Epoch → small period of time
Sea floor spreading evidence
1) Symmetrical Magnetic field reversals
2)New sea floor rock being formed at the ridges
Earliest evidence of life:
stromatolite mounds
3.8 billion years ago
What does this symbol mean
Represents and inclined bed
Original Horizontality
Sedimentary rock layers, or strata were originally deposited as relatively horizontal sheets of sediment. This means that strata that do not retain their original horizontality have
been displaced by movements of the Earth’s crust.
Moraines
material left behind by a moving glacier
-Based on the amplitude of the ground
movement caused by seismic wave
– Accounts for the decrease in wave
amplitude with increased distance
– Mainly for local/nearby earthquakes
Richter scale
Elastic rebound
When a fault is stuck during a movement an excess of energy is stored in the rock, when the force is great enough to break elastic energy is released
Massive erosive force transporting high volumes of sediment downwards and is a major source of water on earth
Streams
Cretaceous Mass Extinction Event
Around 65 million years ago, asteroid impact and resulting climate change caused a mass extinction
Budget
Balance between accumulation
at upper end & ablation at lower end
Hanging wall vs Foot
Hanging wall is the one in movement
Plate boundary types
1)Divergent boundary
2)Convergent boundary
3)Transform fault plane
Location of mid ocean ridges
Mid-Atlantic
East Pacific
Mid-Indian
Iceland Ridge
How did we determine the age of the earth?
Assuming that the earth formed around the same time as the universe we can use meteorite samples to estimate the creation of earth. Since the earth is continuously moving it can be assumed that most of the original rock has been eroded or recycled.
Dating with carbon-14
Half-life of only 5730 years so used to date
very recent events. C-14 is produced in
the upper atmosphere but must be done on organic material
Continental drift
Theory proposed by Alfred Wegener which proposed the super continent Pangea
To better estimate the size of very large earthquakes uses a scale Derived from the amount of displacement along a fault
Moment magnitude scale
Erratics
chunks of rocks transported over long distances by glaciers. When they drop these rocks, they are often far from their origin painting a story of the glaciers path
Anticline
a structural trap formed by the folding of rock strata into an arch-like shape. The rock layers in an anticlinal trap were originally laid down horizontally and then earth movement caused it to fold into an upward arch-like shape
Hydrologic Cycle
the continuous circulation of water in the Earth-Atmosphere system between the ocean,atmosphere, and crust.
highly concentrated combined flow of fluid and sediments under high shear stress in the swash zone, forms small channels
Sheet flow
Fold geometries
1)Symetrical fold
2)Asymetrical fold
3)Overturned fold
4)Recumbant fold
Geological processes from seafloor spreading
1)Basaltic volcanoes
2)Transform faults
3)Normal faults
4)Shallow Eq’s
5)Hydrothermal metas
Smooth surfaces formed by glaciers when sand and other fine grained particles move across rock
Glacial Polish
Porosity
percent of the volume of
material that is pore spaces
Describe the process that causes a disconformity
Represented by an irregular erosional
surface between parallel strata which Implies a pause in the sedimentation plus
erosion, but no tilting
Truncated spurs
Ice chops off the tip to an arete leaving triangular shaped cliffs
Flood planes
a generally flat area of land next to a river or stream. It stretches from the banks of the river to the outer edges of the valley
Focus
source of the EQ on the fault
The Cambrian Explosion
2.5 billion years ago, the oxygen atmosphere formed and First large‐shelled life evolved, Predation evolves, and Burrowing evolves
Continental Dynamics
Continental rock is made of lighter felsic rocks that make it more buoyant and therefore will not subduct
Formula for discharge
Discharge(Q)=Cross sectional area(x)*average velocity(v)
River load carrying
1)Dissolved load-dissolved in water
2)Suspended load-suspended in water
3)Bed load-rolling along the stream bed
Laminar flow
Molecules travel in parallel paths –
no mixing! Flows faster in general
the largest earthquake in a sequence
Mainshock
an underground layer of water-bearing material, consisting of permeable or fractured rock, or of unconsolidated materials (gravel, sand, or silt) moving water from recharge to discharge areas
Aquifer
Nonconformity
metamorphic/igneous rocks in contact with
sedimentary strata
Drainage patterns for steams
1)Dendritic
2)Rectangular
3)Radial
Competence vs Capacity
Competence: max size of object able to be moved by the medium
Capacity:How much material can be carried by a moving medium
What drives plate tectonics
Movement of the plates through
1)Ridge-push
2)Slab pull
3)Trench suction
pull the asthenosphere along
Stream order
As the stream order increases:
- discharge increases
- gradient decreases
- velocity increases
- channel width increases
- channel depth increases
Outwash Plains & Terraces
Sediment choked braided streams
deposit
Process of glacier formation
Snow->Granular snow->firn->ice->flowing ice
Fault
fractures along which displacement occurs
Faults
fractures along which there has been obvious movement on either side of the crack, caused by compression, extension or shearing
Seismic Vibration
Shaking caused by body & surface
seismic waves.
* Severity
– Increases as magnitude
increases
– Decreases with distance from
the causative fault
* Destruction varies considerably
– Type of material built on
– Type of building/structure
Strain types
1)Elastic deformation
2)Plastic deformation
3)Rupture or brittle fracture
Syncline
a place in the earth’s crust where the rock layers curve downward
Types of glacial movement
1)basal slip
2)Plastic flow
Channel pattern types
1)Straight
2)Meandering
3)Braided stream
Precambrian
birth of Earth up to before complex life forms developed (algae, bacteria, some fossils without shells like jellyfish)
Stream Valley types
1)V valley-stream downcuts ex.rapids and waterfalls
2)Wide valley-Downcuts to the base but then erodes the sides in meanders
Acasta Gneiss
Found in the NWT, it is the oldest rock on earth dating to 4.03 billion years ago
the amount of energy
released at the source of the earthquake
Magnitude
Location of oldest and youngest ocean rock
Youngest-> along spreading ridges
Oldest->in W Pacific;
W & E Atlantic
Unconformities
surfaces that represent a gap in the geologic record
How to locate an earthquake
Using three seismograph readings the intersections of the three radius will reveal the location of the epicentre by measuring the difference in arrival time of the P and S waves and use the time travel curve.
Deep Time
geological time or cosmic time, in other words: billions of years.
formed when the particle motion is a combination of both longitudinal and transverse vibration giving rise to an elliptical retrograde motion in the vertical plane along the direction of travel.
Rayleigh wave
Cross-cutting Relationships
Any feature (e.g., a fracture, fault, or intrusive mass of rock) that cuts across a body of sediment or rock is younger than the body of sediment or rock that it cuts
Roche Moutonnees
Formed when ice encounters a bedrock knob, Ice smoothes the up-ice (stoss) side and plucks the down-ice (lee) side
Stress types
1)Shear
2)Compressional
3)Tension stress
Three types of relative age dating
1)Stratigraphy
2)Unconformities
3)Fossils
Elastic Deformation
Deformation that is able to be reversed
Three types of deformation
1)Elastic deformation
2)Ductile deformation
3)Fracture
bowl-shaped, amphitheater-like depressions that glaciers carve into mountains and valley sidewalls at high elevations
Cirque glacier
Alpine Glacier
a glacier that is confined by surrounding mountain terrain
a major type of surface wave having a horizontal motion that is shear or transverse to the direction of propagation, slowest wave type
Love wave
Principles of Stratigraphy
- Original Horizontality
- Stratigraphic Superposition
- Cross-cutting Relationships
- Inclusions
a valley glacier spills out of the mountains, onto the flat foreland, the ice often spreads to form a lobe
Piedmont glacier
Milankovitch Theory
Eccentricity of orbit, Tilt of planet, and
Precession or rotation all are factors that affect global climate
Disconformity
strata on either side of unconformity are parallel
Strain
the reaction of the object
to the stress applied to it – results
in a change in size and/or shape
of a rock.
What does this symbol mean
map symbol for
horizontal beds
Eskers
Winding ridges of drift deposited by streams beneath or within the glaciers that upon melting leave a winding path showing the direction of the original steam
Moraine that marks the furthest
advance of glacier
Terminal moraine
Faunal succession
fossil organisms succeed one another in a
definite order
Joints
cracks in the rocks
along which there has been
no appreciable movement.
the act of a glacier sliding over the bed due to meltwater under the ice acting as a lubricant.
Basal slip
Flood control methods
1)Dams,barriers,and channels
2)Monitoring of water levels
3)Urban planning
Glacial growth
Accumulation
Characteristics of Ocean-Continent convergences
1)Deep focus earthquakes
2)High pressure low temperatures
3)Form subduction zones, trenches, and volcanic arcs
Features of continental glaciers
1)Drumlins
2)Eskers
3)Kettle lakes
4)Kame
Aluvial fans
a triangle-shaped deposit of coarse unsorted grained sediment (sand and gravel) into a dry basin
Varved Clay
fine grained glacial lake sediment that forms in meltwater lakes. The thicker lighter band is deposited in spring/summer melt and the darker thinner band is deposited in winter
Moves at 5km/s, compressional wave type and able to move through a solid or a liquid
P waves
Glacial Drift
Sediments of glacial origin
Normal fault
the hanging wall
has moved down relative to
the foot wall. Due to extensional forces
Location of continental rifts
East African Rift
Rio Grande
Baikal Rift
Rhine Valley
Aretes
Ridge between two cirques or valley glaciers
Surge
sudden period of fast movement for the glacier
Deltas
A build up of sediment along a river mouth. Stream flowing into standing body of water composed of Fine sand, silt and mud
Super continents in Pangea
Laurasia- supercontinent of the Northern Hemisphere made up of the landmasses that currently correspond to North America, Greenland, Europe, and Asia
Gondwanaland-Antarctica was joined to South America, Africa, India, and Australia
The Big One
The Cascadia subduction zone is where the Juan de Fuca, Explorer, and Gorda tectonic plates are subducting under the North American plate. It is now thought to be capable of producing great earthquakes of magnitude 8 or 9
Drumlins
Asymmetrical hills of loose till paralleling ice direction. Steep slope
faces direction of ice movement and the shallow slope is the opposite direction of movement
Correlation
Matching of rock units (formations) of similar
ages in different regions
Angular unconformity
tilted rocks overlain by flat-lying rocks
Regional flood
Produced by storms of long duration, or periods of intense
snowmelt. Saturate soil and cover large area, Flooding on small tributaries may be limited, but cumulative
effect is huge. Cause most of the damage done by floods.
Inclusions
Any part of a pre-existing rock body (clast) that is incorporated into another body of sediment or rock is older than the body of sediment or rock into which it has been incorporated.
debris on side of a glacier
Lateral moraine
Characteristics of Ocean-Ocean convergences
1)Form volcanic arcs
2)Deep focus earthquakes
3)Subduction zones,trenchs, magmatic arc
Ductile Deformation
plastic deformation – Deformation that occurs beyond the elastic limit – irreversible)
The Mohorovičič Discontinuity
the boundary zone between Earth’s crust and the mantle. This boundary marks a change in seismic-wave velocity from the crust to the uppermost mantle within the (lithospheric) plate.
ice closest to the bedrock, experiences extreme pressure from the weight of the ice above and begins to flow like magma
Plastic flow
Eras
Cenozoic - recent life (mammals, humans)
Mesozoic - age of middle life(dinosaurs, 1st scrawny mammals)
Paleozoic - ancient life(fish, trilobites, clams,
corals, ferns)
Fracture
Accumulated strain breaks rock – brittle deformation
3 types of convergent plate boundaries
1)Ocean Continent
2)Ocean-Ocean
3)Continent Continent
Move at 2km/s, move in a shearing motion and can only travel through solids
S waves
Plunging fold
the fold axis is inclined from
the horizontal creating a V outcrop above the plane
Ophiolites
pieces of oceanic plate that have been thrusted (obducted) onto the edge of continental plates
1)Sediments,
2)Basaltic lavas,
3)Pillow lavas,
4)sheeted dykes
5)Gabbro,
6)Peridotites (ultramafic
a “permanent” stream or
sheet of ice able to flow
Glacier
Unsorted material deposited in lakes or oceans from melting of
calving icebergs
Glacial Marine drift
Half-life
the time required for one-half of the
radioactive nuclei in a sample to decay
Radioactive Decay
Matter transforms from unstable to stable energy states.Radioactive materials are substances which spontaneously emit
various combinations of ionising particles (alpha and beta) & gamma rays of ionising radiation to become more stable.
Stratified drift
Deposited by meltwater streams - Better sorting and rounding
Striations
parallel scrape marks on bedrock give
direction of flow
Large fragments from
icebergs that deform sediments
they fall into
Dropstones
Causes stream erosion
1)Abrasion
2)Chemical and physical weathering
Strike-slip fault
the movement is lateral, parallel to the fault plane. Due to shearing forces.
dextral (right lateral)
sinistral (left lateral
Kettle lakes
Form where blocks of ice
that have fallen off the front of the glacier become buried and then melt in the depressions forming kettle lakes
Stress
the force applied to an
object, causes strain
rocks with distinctive stratigraphy
and structural history that appear to have formed elsewhere!
Terrane
Characteristics of continent-continent convergences
1)Form suture zones
2)Intensely folded mountain ranges,thrust faults, large batholiths,shallow earthquakes
What does this symbol mean
map symbol for
vertical beds
Tsunamis
a tsunami is almost always caused by an earthquake under water. In the open ocean height usually < 1 m
In shallower coastal areas water piles
up to heights occasionally > 30 m
Earliest humans and the
Pleistocene Glaciation
3-4 MA occurs in the czenoic era
Reverse fault
the hanging wall has
moved up relative to
the foot wall. Due to compressional forces
Dip
the angle the rock
plane is inclined from
the horizontal.
(measured angle to strike)
Causes of ice ages
1)Ocean circulation changes
2)Massive long duration volcanic eruptions
3)Solar energy variation
Factors affecting stream velocity
1)Position within the channel
2)Lower cross sectional area=faster
3)Smoother=faster
4)bigger=faster
5)Steeper=faster
downward limit to which a stream can cut/erode host rock
base levels
Fjord
Steep sided inlet to the sea
Permeability
the ability of a
material to transmit a fluid
Causes of glacial ablation
Melting, Calving,
Sublimation, Wind erosion
