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Profile illustrating the shelf, slope and rise. A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters.It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges.
The continental shelf and the slope are part of the continental margin. [6] The shelf area is commonly subdivided into the inner continental shelf, mid continental shelf, and outer continental shelf, [7] each with their specific geomorphology [8] [9] and marine biology. [10]
Because the continental rise lies below the continental slope and is formed from sediment deposition, it has a very gentle slope, usually ranging from 1:50 to 1:500. [1] As the continental rise extends seaward, the layers of sediment thin, and the rise merges with the abyssal plain, typically forming a slope of around 1:1000.
While many oceanic plateaus are composed of continental crust, and often form a step interrupting the continental slope, some plateaus are undersea remnants of large igneous provinces. Continental crust has the highest amount of silicon (such rock is called felsic). Oceanic crust has a smaller amount of silicon (mafic rock).
A submarine canyon is a steep-sided valley cut into the seabed of the continental slope, sometimes extending well onto the continental shelf, having nearly vertical walls, and occasionally having canyon wall heights of up to 5 km (3 mi), from canyon floor to canyon rim, as with the Great Bahama Canyon. [1]
The continental shelf is a gently sloping benthic region that extends away from the land mass. At the continental shelf edge, usually about 200 metres (660 ft) deep, the gradient greatly increases and is known as the continental slope. The continental slope drops down to the deep sea floor.
The outer continental shelf and slope may be cut by great submarine canyons, which mark the offshore continuation of rivers. At high latitudes and during glaciations, the nearshore morphology of passive margins may reflect glacial processes, such as the fjords of Greenland and Norway.
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