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22 Cards in this Set
- Front
- Back
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abyssal hill |
small sediment-covered inactive volcano or intrusion of molten rock less than 200 meters high, thought to be associated with sea floor spreading. abyssal hills punctuate the otherwise flat abyssal plain |
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abyssal plain |
flat, cold, sediment covered ocean floor between the continental rise and oceanic ridge at a depth of 3,700 to 5,500 meters. abyssal plains are more extensive in the Atlantic and Indian Oceans than the Pacific |
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active margin |
the cotinental margin near an area of lithosphere plate convergence; also called Pacific-type margin |
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bathymetry |
the discovery and study of submerged contours |
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continental margin |
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 |
the wedge of a sediment forming the gentle transition from the outer (lower) edge of the contiental slope to the abyssal plain; usually associated with passive margins |
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continental shelf |
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 |
the sloping transition between the granite of the continent and the basalt of the seabed; the true edge of a continent |
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fracture zone |
area of irregular, seismically inactive topography marking the position of a once-active transfrom fault |
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guyot |
a flat-topped, submerged inactive volcano |
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hydrothermal vent |
a spring of hot, mineral-and-gas rich seawater found on some oceanic ridges in zones of acive seafloor spreading |
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ice age |
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 |
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island arc |
curving chain of volcanic islands and seamounts almost always found paralleling the concave edge of a trench |
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ocean basin |
deep-ocean floor made of basaltic crust (compare continental margin) |
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oceanic ridge |
young seabed at the active spreading center of an ocean, often unmasked by sediment, bulging above the abyssal plain. the boundary between diverging plates. often called a mid-ocean ridge, though less than 60% of the length exists at mid-ocean |
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passive margin |
the continental margin near an area of lithosperic pate divergence; also called Atlantic-type margin |
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seamount |
a circular or elliptical projection from the seafloor, more than 1 kilometer in height, with relatively steep slope of 20 to 25 degrees |
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shelf break |
the abrupt increase in slope at the junction between continental shelf and contiental slope |
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submarine canyon |
a deep, v shaped valley running roughly perpendicular to the shoreline and cutting accross the edge of the continental shelf and slope |
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transfrom fault |
a plane along which rock masses slide horizontally past one another |
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trench |
an arc-shaped depression in the deep-ocean floor with very steep sides and a flat sediment-filled bottom coinciding with subduction zone. most trenches occur in the Pacific |
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turbidity currents |
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 |
