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90 Cards in this Set
- Front
- Back
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What is the shape of the earth?
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The earth is an oblate ellipsoid
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Why is the earth not perfectly spherical
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Newton (1687)- As the earth rotates, equator moves faster than the poles, the outward force of the earth's rotation produces a bulge in the equator
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Circle of Illumination
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divides daylight and darkness on the globe
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subsolar point
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point at which the sun's rays hit directly (e.g. at 90 degrees)
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Declination
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latitude of subsolar point
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approximate radius of earth
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6400km
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Define seasons
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Cyclical changes in temperature that occur throughout the year -- caused by changes in the amount of solar energy received
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Dates of equinox, summer and winter solstice
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Equinox: March 21, September 22
Summer solstice: June 21 Winter Solstice: December 21 |
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aphelion
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farthest position from the sun (July 4)
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perihelion
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closest position from the sun (Jan 3)
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revolution
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movement around the sun (the speed and distance at which the earth is moving affects the duration of the seasons)
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inclination
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tilt of the earth's axis (with respect to a line on the plane of the ecliptic, which is on the equator)
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polarity
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orientation of axis- parallel throughout the year (affects when seasons occur)
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what is solar insolation?
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the solar radiation striking earth or another planet (measured in watts/m2)
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earth's inclination
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23.5 degrees
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latitude
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the angular distance north or south of the equator
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longitude
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the angular distance east or west of a point on the earth's surface
prime meridian= greenwich, UK |
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location of north pole
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90degrees N
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GPS
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Global positioning system-- calculates lat/long and elevation within 1m of accuracy
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Remote sensing
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info acquired at a distance without physical contact of subject (e.g. a radar)
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GIS
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Geographic Information system-- integrates hardware, software, and data for capturing, managing, analyzing and displaying all forms of geographically referenced information
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Azimuthal system of bearings
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North- 0 to 360
East- 090 South- 180 West- 270 |
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longitude based on differences in time
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15 degrees= 1 hour
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use of N star to determine latitude
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Star directly ahead (at N pole)-- latitude 90 degrees
Star on horizon at equator-- latitude 0 degrees star x degrees above horizon-- latitude x degrees |
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what is the importance of local noon?
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at local noon, the sun is at its highest angle above the horizon
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p-waves
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primary (compression)- straight waves
-seismic wave generated by earthquakes |
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s- waves
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secondary (shear) waves-- do not travel through liquids
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four layers of the earth (solid/liquid)
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inner core: solid
outer core: liquid mantle: solid crust: solid |
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approximate thickness of crust
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8-40km
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thickness of mantle
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2900km
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thickness of core
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3500km
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rock
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natural aggregate of minerals
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minerals
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naturally occuring, inorganic crystalline solid with a definite chemical composition and characteristic physical properties
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3 most abundant element at earth's crust
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Oxygen, Silicone and Aluminum
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Chemical formula for quartz
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Si02
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3 ways that minerals form
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1. cooling from liquid (magma, lava) to solid state
2. evaporation of briny (salty) liquid 3. precipitation from a fluid |
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igneous rock
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(fire formed) rock that solidified and crystalized from a molten state e.g. granite, basalt, obsidian, pumice
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magma
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molten rock beneath the earth's surface
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lava
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molten rock above the earth's surface
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what's the difference between intrusive and extrusive igneous rocks? how do these differences relate to cooling history and crystal size?
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intrusive rocks- cool under earth's surface (slower than at surface), allow larger crystal sizes to grow
extrusive rocks- cool above earth's surface- smaller crystal sizes |
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weathering
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surface processes that physically disrupts and chemically change rocks
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sediment
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fine grained mineral matter transported by transported by air, water or ice
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sedimentary rocks
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formed by erosion, transportation, deposition, compaction, cementation, and hardening of sediment
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3 types of sedimentary rocks
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clastic
chemical organic |
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clastic sedimentary rocks
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derived from weathered and fragmented rocks
e.g. mudstone, shale, sandstone |
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chemical
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dissolved minerals
- transported in solution and precipitated e.g. limestone and evaporates |
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organic
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remains of dead organisms
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metamorphic rocks
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rocks changed by heat or pressure
- changes structure, texture, composition and appearance of parent rock - commonly at roots of mountains - does not involve melting |
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primary difference between metamorphic and igneous rocks
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heat and pressure has been applied to a metamorphic rock that used to be an igneous rock
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2 types of geologic dating
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relative= sequential age
numerical= number (absolute) age |
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geologic contacts
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boundary between different rocks
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deformation
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process that fault and fold rocks
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unconformity
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there has been some kind of erosion
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isotopes
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atoms of the same element can have different numbers of neutrons, different possible versions of each element are called isotopes
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half- life
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time required for half of the original parent atoms to decay to their daughter
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decay constant
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rate at which isotope decays (per year)
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what assumptions are necessary for radioactive dating?
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- decay occured at constant rate
- isotope system has remained a closed system since the rock formed |
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what rocks are suitable for radioactive dating
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igneous rocks= very good
sedimentary rocks= poor metamorphic rocks= maybe |
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how old are rocks on earth?
how old is the earth? |
3.96 billion years old
earth: 4.6 billion |
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why are there no rocks as old as the earth?
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difficult to find older rocks because earlier crusts destroyed
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traditional theory of fixed continents
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continents and ocean basins fixed in position (used until 1968)
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problems with theory of fixed continents
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- matching continent edges, matching fossils among continents, matching geology among continents, Isostasy
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Plate tectonics
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process for continental drift
- thermal convection system within earth 1. making crust 2. destroying crust |
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what parts of the earth's layers make up a tectonic (Ithospheric) plate?
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chemical classification: crust; physical classification: lithosphere
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3 major types of plate boundaries
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1. spreading (pulling apart)
2. converging (plates pushing together) 3. transform (plates pass each other) |
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what do tectonic plates float on and how much melt is present at this layer?
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tectonic plates float on mantle and ~1-5 percent melt is present at this layer
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how is oceanic crust made at spreading boundaries?
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making crust- new crust generated as plates pull away
- magma rises up from mantle and spreads out and cools - occurs at spreading boundaries - process called sea floor spreading |
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most famous spreading zone
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mid- atlantic ridge (from arctic sea to beyond the tip of africa)
- rate of spreading 2.5 cm per yr |
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2 regions where spreading centers interrupt continental crust
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iceland and east africa where the red sea meets the gulf of eden
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3 types of convergent boundaries
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oceanic- oceanic
oceanic- continental continental-continental |
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how is crust destroyed at boundaries? what is the process of crust destruction called?
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crust descends into mantle and is recycled, occurs at converging boundaries called trenches and process is called subduction
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what forms above subducting plate
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a volcanic arc forms above subducting plate
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why does oceanic crust generally subduct? what does this say about age of crusts?
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oceanic crust thinner than continental crust. since oceanic crust continually being destroyed and recreated, it is younger than continental crusts
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most famous transform boundary in N america
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san andreas fault
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3 modern pieces of evidence for plate tectonics
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paleomagnetism: alternating bands of reversed polarity-- same pattern on both sides of ridge
radiometric dating- increased distance from ridge-- increased age sediment thickness- increased distance from ridge-- increased thickness |
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what is the primary way to measure plate movements in the modern world?
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GPS- station position changes as plates move
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relief ratio
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total relief/ radius
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earth's relief
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19km/6400km= 0.003
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orogeny
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mountain bulding episode
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limestone
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sedimentary rock composed of calcite, commonly forms from remains of marine organisms
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rock stress
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from tectonic forces, gravity, and weights of rocks above
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3 types of rock stress
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tension (stretching_
compression (shortening) shear (twisting or tearing) |
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strain
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how rocks respond to stress
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2 types of rock strain
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folding (bending)
faulting (breaking) |
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types of folds
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anticline
syncline |
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anticline
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simple upfold
Layers slope down from axis, youngest on the outside) |
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syncline
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simpple downfold
layers slope up from axis youngest on the inside |
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faulting
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rocks on either side of a fracture are displaced relative to each other
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3 types of faults
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normal (tension)
reverse (compression) ** results in dip slip or vertical compression strike-slip (transcurrent) ** results in shearing or lateral displacement |
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fault scarp
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steep cliffs that make up the edge of a displaced block
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