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31 Cards in this Set
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- Back
Abyssal Hill
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Small sediment-covered inactive volcano or intrusion of molten rock less than 200 meters (650 feet) high, thought to be associated with seafloor spreading. Abyssal hills punctuate the otherwise flat Abyssal plain.
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Abyssal Plain
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Flat, cold, sediment-covered ocean floor between the continental rise and the oceanic ridge at the depth of 3,700 to 5,500 meters (12,000 to 18,000 feet). Abyssal plains are more extensive in the Atlantic and Indian oceans than the Pacific.
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Active Margin
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The continental margin near an area of lithospheric plate convergence; also called Pacific-type margin.
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Bathymetry
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The discovery and study of submerged contours.
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Continental Margin
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The submerged outer edge of a continent, made of granitic crust; includes the continental shelf and continental slope. Compare ocean basin.
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Continental Rise
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The wedge of sediment forming the gentle transition from the outer (lower) edge of the continental slope to the abyssal plain; usually associated with passive margins.
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Continental Shelf
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The gradually sloping submerged extension of a continent, composed of granitic rock overlain by sediments; has features similar to the edge of the nearby continent.
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Continental Slope
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The sloping transition between the granite of the continent and the basalt of the seabed; the true edge of the continent.
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Deep Scattering Layer (DSL)
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A relatively dense aggregation of fishes, squid, and other mesopelagic organisms capable of reflecting a sonar pulse that resembles a flat bottom in the ocean. Its position varies with the time of day.
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Deposition
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Accumulation, usually of sediments.
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Earthquake
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A sudden motion of Earth's crust resulting from waves in Earth caused by faulting of the rocks or by volcanic activity.
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Fracture Zone
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Area of irregular, seismically inactive topography marking the position of a once-active transform fault.
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Guyot
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A flat-topped, submerged inactive volcano.
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Hydrothermal Vent
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A spring of hot, mineral and gas rich seawater found on some oceanic ridges in zones of active seafloor spreading.
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Ice Age
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One of several periods (lasting several thousand years each) of low temperature during the last million years. Glaciers and polar ice were derived from ocean water, lowering sea level at least 100 meters (328 feet).
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Ice Cap
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Permanent cover of ice; formally limited to ice atop land, but informally applied also to floating ice in the Arctic ocean.
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Iceberg
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A large mass of ice floating in the ocean that was formed on or adjacent to land. Tabular icebergs are tablelike or flat; pinnacled icebergs are castellated, or jagged. Southern icebergs are often tabular; northern icebergs are often pinnacled.
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Island Arc
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Curving chain of volcanic islands and seamounts almost always found paralleling the concave edge of a trench.
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Ocean Basin
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Deep-ocean floor made of basaltic crust. Compare continental margin.
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Oceanic Ridge
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Young seabed at the active spreading center of an ocean, often unmasked by sediment, bulging above the abyssal plain. The boundary between deverging plates. Often called a mid-ocean ridge, though less than 60% of the length exists at mid-ocean.
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Orbital inclination
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The 23*27' "tilt" of Earth's rotational axis relative to the plane of its orbit around the sun.
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Passive Margin
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The continental margin near an area of lithospheric plate divergence; also called Atlantic-type margin.
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Sea Level
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The height of the ocean surface. (mean sea level)
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Seamount
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A circular or elliptical projection from the seafloor, more than 1 kilometer (0.8 mile) in height, with a relatively steep slope of 20* to 25*.
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Shelf Break
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The abrupt increase in slope at the junction between continental shelf and continental slope.
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Submarine Canyon
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A deep, V-shaped valley running roughly perpendicular to the shoreline and cutting across the edge of the continental shelf and slope.
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Telepresence
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The extension of a person's senses by remote sensors and manipulators.
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Transform Fault
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A plane along which rock masses slide horizontally past one another.
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Trench
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An arc-shaped depression in the deep-ocean floor with very steep sides and a flat sediment-filled bottom coinciding with a subduction zone. Most trenches occur in the Pacific.
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Turbidity Current
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An underwater "avalanche" of abrasive sediments thought responsible for the deep sculpturing of submarine canyons and a means of transport for sediments accumulating on abyssal plains.
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Turbulence
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Chaotic fluid flow
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