Bottom abyssal currents as a geomorphic factor

Abstract

Recent sea floor studies revealed a planetary system of bottom abyssal currents which embraces the whole floor of the World Ocean abyssal zone. The currents are generated mainly by cool water of the Antarctic shelves, the water due to its high density descends and flows along the continental slope and then spreads over all the ocean floor basins including those in the Northern hemisphere. Arctic and Subarctic deep water adds to the near-bottom currents (f, e. Sea of Okhotsk). Sometimes bottom abyssal currents result from dense water of abnormally high salinity. Bottom abyssal currents velocity may exceed 10 cm/sec, sometimes up to l meter per sec, they can erode sea floor and form abyssal valleys, transport enormous masses of suspended matter (near-bottom clouds-nepheloides) and deposit them where the flow descelerates, forming huge piles of sediments («sedimentary ridges»). Sometimes these currents are responcible for lack of sediments and considerable gaps in geological records. The current activity may change considerably through the geologic history.