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135 Cards in this Set
- Front
- Back
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Mass Wasting
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Landslide
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Rock Falls
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High velocity landslide where large boulders free fall through the air due to gravity
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Rock Slides
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Pre-existing layering in the same direction as the slope and entire slabs fall off
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Slumps
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Material slides down and toe shoots out
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Flows
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wet landslides where material is saturated and turned to slop
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What controls landslides?
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• Water
• Vegetation • Rock layering • Earthquakes |
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Angle of repose
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The max angle at which stuff can be piled up
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Fine Sand
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35 degrees
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Coarse Sand
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40 Degrees
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Pebbles
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45 Degrees
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Order of sand cohesiveness
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damp sand, dry sand, saturated, wet sand
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Creep
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a fracture along the top layer of bedrock - slow moving
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stream
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every flowing body of water
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What sediments do streams carry?
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dissolved ions, suspended load, bed load
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Head/Source
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the beginning of a stream, the highest elevation
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Mouth
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the end of the stream where it deposits
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competence of a stream
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largest particles it can carry/move
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Capacity of a stream
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measure of total sediment load
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What happens to competence as the stream heads towards the mouth?
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Competence decreases as it gets closer to the mouth
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what happens to capacity as the stream gets closer to the mouth?
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Capacity increases as it gets closer to the mouth
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How do streams maintain graded profiles?
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erosion/deposition
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what happens to valleys over time?
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They get deeper and wider
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Explain a meandering River
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○ The water on the outside bend has to speed up
○ The sediment is eroded - picks up sediment ○ Sediment is deposited on the inner curve - point bar ○ The outside cuts a steep outer wall - cut bank |
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Oxbow lakes
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lakes where a curve of the river has become detached because of erosion and deposition
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flood plain
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the flat land surrounding the river
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How are the twists preserved?
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uplifting of rock
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alluvial fan
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large area of deposited sediment at mouth
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Ocean
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97.2%
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Ice and Snowfields
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2.1%
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Groundwater
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0.6%
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Lakes and rivers
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0.02%
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atmosphere
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0.001%
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Pore spaces
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open spaces in the rock
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porosity
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the volume of sediment over total volume
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porosity and clast size
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fine grained have lower porosity
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porosity and angularity
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angular clasts have lower porosity
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porosity and sorting
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poorly sorted grains have lower porosity
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porosity and cementation
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well cemented grains have lower porosity
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porosity and rock type
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igneous and metamorphic rocks are typically less porous than sedimentary rocks
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permeability
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the measure of how connected the pore spaces are
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a good flow requires
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high porosity and high permeability
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aquifer
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high permeability
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aquitard
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low permeability
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aquiclude
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no permeability
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water table
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boundary between saturated and unsaturated rock
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what does a water table generally follow?
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topography
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what happens if a water table intersects the surface of the earth?
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Surface water
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Watershed
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defines where drainage goes - how groundwater flows, the land surface that drains into a particular body of water
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Drainage divides
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watershed boundaries
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what is the problem with asphalt?
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it prevents the water from percolating and getting cleaned by the sediment
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Cone of depression
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when a well sucks up the water a cone is formed around the well of de-saturated rock.
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What happens with the salt/freshwater boundary with development?
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it moves closer inland as the freshwater is sucked up
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How does a wave come in?
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• The shallow water causes the bottom of the wave to drag and it curls into a crashing wave
• The outside of the wave is still in deep water and moves faster • The wave starts to bend Still approaches the shore at an angle, but a gentle one |
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long shore current
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• Long shore current - water and sand are moved, sand is moved parallel to the shoreline
○ The "beach towel" phenomenon |
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Jetty
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a long structure built perpendicular to the shore that builds up sand and prevents inlets from moving
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groin
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a wall perpendicular to the shore that builds up sand
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what happens to barrier islands as sea level rises?
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they more inland
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what happens as sand from the barrier islands gets closer to the shore?
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the waves break more gently and the land gets moved back up
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if you're standing on a beach, where did that spot used to be?
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a sound
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Wave Refractions
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wave travels and as it gets closer to shore part of it is in shallow and part in deep, so the wave bends as it approaches the shore (nearly parallel)
○ Cause of longshore current |
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wave reflection
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hits the shore and dissipates energy
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what influences wave height? (?)
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The depth to which the water particles are moving depends on wave height
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What happens to particle motion as the water gets more shallow?
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they flatten out
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why does a wave break?
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the top is moving faster than the bottom
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Rocky coastlines
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• More durable
• Erode seacliffs back • Maintains steep cliff as chunks fall off • Moves backward |
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Wave cut terraces
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either uplift of coast or decrease of sea level, episodic
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Fault
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a fracture where two rock masses have moved past each other
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Dip-Slip fault
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vertical
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strike-slip fault
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horizontal
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Normal fault
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□ Hanging wall moves downward
□ Divergent plate boundary □ Crustal extension |
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Reverse fault
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□ Hanging Wall moves upward
□ Crustal shortening □ Convergent |
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Rocks are much better at ________ than _____________
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Rocks are much better at being compressed than maintaining tension
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which earthquakes are worse?
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convergent because rocks are stronger in shortening and thus more energy and tension is created
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Thrust fault
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○ Repetition in layering
○ Pushes the layers out and over the others ○ Strata layers repeated usually indicates thrust fault ○ Typical of convergent plate boundaries |
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how fast is LA moving?
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approx 5 cm per year
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folding
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ductile behavior
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strecthing
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when strata are pulled thin
(divergent?) |
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shearing
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rocks are pulled and broken
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faulting
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brittle behavior
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Composition
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Layered material is weaker and thus easier to fold
(shale is easier to fold than granite) sedimentary rocks are weaker |
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Time - "Strain rate"
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○ The faster you deform something, the more brittle it is
§ Slow - ductile § Fast - brittle |
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Pressure
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shallow is brittle, deep is ductile
At greater depth, rocks are surrounded by other rocks and experience more pressure that keeps it intact |
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Temperature
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○ High temperature is ductile
○ Low temperature is brittle |
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Elastic Rebound Theory
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Slow plate motion start and energy is released quickly. Energy builds up slowly and quickly releases
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Focus/hypocenter
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-the initial rupture of an earthquake
-Sends out vibrations and propagates out |
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0 seconds
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rupture expands circularly on fault plane sending out seismic waves in all directions
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10 seconds
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the rupture progresses down the fault plane, reducing the stress and allowing rocks on either side to rebound
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20 seconds
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rupture progresses along maximum length of fault, displacement occurs and earthquake stops
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the strength of the earthquake depends on
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how big a patch is ripped
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Where is the focus?
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the initial point of the quake, usually not at the surface because compressional pressure is necessary
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Strain accumulation over time
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buildup and elastic rebound
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the _____________ of rocks is important in considering the effects of an earthquake
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composition of the rock
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maximum depth of convergent plate bounndary
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~800 KM
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maximum depth divergent
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~30 KM
- hot and thus can't help support elastic strain energy |
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P-Wave
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"primary wave"
○ Pulse that is coming through the rock § Like pumping a slinky § Travels the fastest § Sharp BANG! |
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S-Wave
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"secondary wave"
○ Result in a lot more motion ○ Through the rock (wiggly) ○ Shakes you harder ○ Does more damage |
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Surface Wave
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○ Travels along the surface of the earth
○ Amplitude decreases as it travels through the earth ○ Looks like the ground has turned into ocean waves ○ Do a lot of damage |
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Seismograph
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gages motion of earth
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Magnitude
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Measurement of energy released
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Intensity
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Measure of damage done
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Richter scale
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-measures magnitude
-how much the ground moves |
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Movement Magnitude Scale
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concerned with how much size (area) of fault rupture displacement
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every step on the richter scale is __ times the amplitude and __ times the energy
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10,32
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What is the max range of the richter scale?
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1-9.5
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Why is there a maximum to the richter scale?
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because the rocks can only hold so much energy
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What makes the biggest earthquakes?
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asteroid impacts
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what was the approximate impact of the KT boundary?
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12
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how many earthquakes accounted for half of the last century's earthquake energy?
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3
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Modified Mercalli Intensity Scale
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uses roman numerals to express damage done by earthquakes
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I
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Not felt
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II
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Rest
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III
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Indoors
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IV
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indoors
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V
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Felt by all
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VI
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chimneys
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VII
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Run outside
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VIII
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well built buildings damaged
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IX
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buildings shifted off foundation
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X
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some well built buildings destroyed
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XI
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Few masonry buildings remain standing
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XII
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damage total
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What material fares the best?
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Wood
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vertical acceleration is greater than
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1G
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What controls variations in intensity?
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○ Type of structures
○ Location in relation to water § Sediments move easier in water logged area ○ Bedrock geology |
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the san andreas fault produces about __ Magnitude __ earthquake every ___ years
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1,8,100
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it would take approximately ___ magnitude 5 earthquakes to dissipate the energy of __ magnitude 8
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320 (approx 1 every day) 1 magnitude 8
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what happened in 1811-1812?
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• 4 magnitude 8 earthquakes occurred in 2 months - Arkansas 1811 - 1812
○ SE Missouri, NE Arkansas ○ The Mississippi changed course |
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seismic energy is dissipated faster in the ______
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west
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The crust is harder in the ____ and thus the damage is less severe than the _____
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• The crust is harder in the east and thus the damage is less severe than the west
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The waves travel farther in the ___
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east
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What is delta T?
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the time inbetween the P and S waves
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we can find the epicenter if we have ___ parties counting seconds
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3
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We need to know the _____,____,and _____ to have useful information about an earthquake
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magnitude, date, place
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how many earthquakes have been successfully predicted?
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1 in China in 1975
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how did they know the earthquake was coming?
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the animals were acting strangely and the water levels were changing
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