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59 Cards in this Set
- Front
- Back
The continental shelf and the steeper continental slope lie:
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Under water along the edges of continents.
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Submarine canyons are cut into the continental slope and outer continental by:
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Turbidity currents, sand flow and fall, bottom currents, and river erosion during times of lower sea level.
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What are turbidity currents?
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A flowing mass of sediment-laden water that is heavier than clear water and therefore flows donslope along the bottom of the sea or a lake.
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Abyssal fans form:
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As sediment collects at the base of submarine canyons.
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A passive continental margin occurs:
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Off geologically quiet coasts and is marked by a continental rise and abyssal plains at the base of the continental slope.
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The continental rise and abyssal plains form:
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From sediment deposited by turbidity currents.
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Continental rise may also form from:
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Sediment deposited by contour currents at the base of continental slope.
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Contour currents are:
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A bottom current that flows parallel to the slopes of the continental margin.
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An active continental margin is marked by:
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An ocean trench at the continental slope.
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What are associated oceanic trenches?
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Benioff zones of earthquakes and andesitic volcanism.
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What is the mid-oceanic ridge?
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A globe-circling mountain range of basalt, located mainly in the middle of ocean basins.
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What are fracture zones?
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Lines of weakness that offset the mid-oceanic ridge.
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Sea Mounts are:
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Conical, submarine volcanoes that are now mostly extinct.
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What are Guyots?
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Flattopped seamounts, probably leveled by wave erosion before subsiding.
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Chains of seamounts and guyots form what?
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Aseismic ridges.
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Corals and algae living in warm, shallow water construct what?
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Fringin reefs, barrier reefs, abd atolls.
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Terrigenous sediment is composed of what?
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Land-derived sediment deposited near land by turbidity currents and other processes.
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Pelagic sediment is composed of what?
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Wind-blown dust and microscopic skeletons that settle slowly to the sea floor.
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What does the mid-oceanic ridge lack?
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Pelagic sediment.
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Oceanic crust consists of what?
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Basalt pillows and dikes, probably overlying gabbro.
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Ophiolites in continental mountain ridges represent what?
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Slivers of somewhat atypical oceanic crust somehow emplaced on land.
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How old are the oldest rocks on the deep sea floor?
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200 million years old.
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Plate tectonics
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The theory that the earth's surface is divided into large plates.
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Who is Alfred Wegener?
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A meteoroligist that proposed the theory of continental drift and Pangea.
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What evidence is there of continental drift?
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Careful fits of continental edges and detailed rock matches between now-sparated continents.
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What is Hess's hypothesis of sea-floor spreading?
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The sea floor moves away from the ridge crest and toward trenches as a result of mantle convection.
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Sea-floor spreading explains trenches as what?
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Sites of sea-floor subduction, which causes low heat flow and negative gravity anomalies.
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Sea floor spreading also explains what?
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The young age of rock of the sea floor as caused by the loss of old sea floor through subduction into the mantle.
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Plates are composed of what?
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Blocks of lithosphere riding on a plastic asthenosphere.
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What is Vine and Matthews?
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It's the hypothesis that gives the rate of plate motion and can predict the age of the sea floor before it is sampled.
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Divergent plate boundaries are marked by what?
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Rift valleys, shallow-focus earthquakes, high heat flow, and basaltic volcanism.
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Transform boundaries are marked by what?
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Strike-slip faults and shallow-focus earthquakes.
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Convergent plate boundaries can cause what?
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Subduction or continental collision.
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What are convergent plate boundaries marked by?
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Trenches, low heat flow, Benioff zones, andesitic volcanism, and young mountain belts or island arcs.
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Plate motion was once thought to be caused by what?
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Mantle convection.
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What is plate motion now attributed to?
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Cold, dense, leading edge of a subducting plate pulling the rest of the plate along with it.
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Trench suction:
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Helps continents to diverge.
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Mantle plumes are:
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Narrow columns of hot, rising mantle rock that cause flood basalts and may split continents , causing plate divergence.
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Earthquakes usually occur when?
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When rocks break and move along a fault to release strain that has gradually built up in the rock.
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Seismic waves move where?
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The move out from the earthquake's focus.
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Body waves move where?
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Move through Earth's interior.
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Surface waves move where?
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On Earth's surface.
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What are seismographs?
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A seismometer with a recording device that produces a permanent record of Earth motion.
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The time interval between first arrivals of P and S waves is used to determine what?
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The distance between the seismograph and the epicenter.
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Earthquake is determind and measured by:
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assessing damage and on the midfied Mercalli scale.
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How is magnitude tested?
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On the Eichter scale
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Most of the world's earthquakes are located where?
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The circum-Pacific belt.
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Divergent plate boundaries are marked by what?
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A narrow zone of shallow earthquakes along normal faults, usually in a rift valley.
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Transform boundaries are marked by what?
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By shallow quakes caused by strike-slip motion along one or more faults.
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Convergent boundaries are marked by what?
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A very broad zone of shallow quakes and Benioff zones.
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Atoms are composed of what?
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protons, neutrons, and electrons. A given element always has the same number of protons.
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What is an ion?
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An atom in which the positive and negative electric charges do not balance.
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Ions or atoms bond together in what?
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Orderly 3-D crystalline structures.
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A crystalline substance is considered what?
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A mineral if it is naturally occurring and has a specific chemcial composition.
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The three most abundant elements in the earth's crust are what?
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Oxygen, silicon, abd aluminum.
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Most minerals are what?
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Silicates.
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What are the most common minerals in the earth's crust?
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Feldspars. The next are quartz, the pyroxenes, the amphiboles, and the micas. All silicates.
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Minerals are usually identified by what?
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Their physical properties.
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What are the physical properties?
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Cleavage, crystal form, fracture, hardness, luster, color, streak, and specific gravity.
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