Abyssal Plains

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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Abyssal Plains


deepwater plains of ocean basins and depressions of epicontinental seas. They are found within the bounds of the ocean floor and in the transitional zone and are divided into two morphological types—flat, or subhorizontal, and hilly. Flat abyssal plains are confined to the margins of ocean basins or to the centers of the basins of epicontinental seas. Hilly abyssal plains occupy a large part of the bottom of the ocean floor. The surface of the flat abyssal plain is characterized by exceptional evenness, with floor gradients of less than 0.001. Starkly contrasting solitary seamounts, evidently of volcanic origin, are also found. Flat abyssal plains are most widely found in the Atlantic (Hatteras, Biscay, Angola, and so forth). Their evenness is caused by the fact that they are unique traps that catch loose sediment (foraminiferal and diatomaceous silts and marine glacial deposits in polar waters).

The hilly abyssal plains show significant ruggedness. Relative variations of depth are from 500 to 1,000 m. The surface is a combination of hills and ridges separated by depressions; solitary seamounts are also frequently found. The floor is covered by deepwater deposits. Hilly plains are most widely found in the Pacific and Indian oceans and to a lesser degree in the Atlantic.


Leont’ev, O. K. Kratkii kurs morskoi geologii. Moscow, 1963.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Scientists know little about the benthic (deep-sea) species residing in the abyssal plains, but what they're learning shows them to be highly adapted to an extreme environment, where temperatures hover just above freezing and pressures become crushing.
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Plate and the western margin of the Indian Plate and continued further south-westward in the Gulf of Oman abyssal plain. We support the notion of Critelli and De Rosa (1987) and Critelli et al.
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The bathyal level, the abyssal plains, and the great oceanic trenches represent more than 80% of the ocean bottom, and thus more than half of the surface of planet Earth.
Rare, very large turbidity currents periodically deposit thick sequences of sediment on oceanic abyssal plains, but their return periods span many thousands of years.
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Much of the plateau is in water shallower than 2,000 meters, but it is surrounded on three sides by abyssal plains more than 4,500 meters deep.
After 15 years of researching deep-ocean sedimentation, Orrin Pilkey realized that at cocktail parties people would listen more attentively when he talked about coastal erosion, hurricanes, and shoreline processes than about turbidity currents and abyssal plains. He subsequently stopped going on deep-sea research cruises and started going to the beach.
Now that the deep sea mining of polymetallic nodules on the abyssal plain (4000 to 6000 m depth) of the central Eastern Pacific is to begin in the next few years, serious consideration must be given to the possible effects on the abyssal environment.