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59 Cards in this Set

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