Submarine Canyons

steep-sloped, often U-shaped and branching valley-like landforms that cut deeply (up to 1-2 km) into the submarine edges of continents. The submarine canyons usually begin on the shelf at a depth of several scores or hundreds of meters and terminate at the base of the continental slope or within the continental rise at a depth of 2-4 km. Outcroppings of bedrock are encountered in the sides of the submarine canyons; in the lower portion of the canyons lie debris fans that at times reach enormous sizes (with radii on the order of 300-350 km). Some submarine canyons are related to river valleys; in these instances they are the submarine continuations of these valleys (including those of the Congo, Indus, Ganges, and Amazon). In many instances, lee currents have probably been involved in the formation of the submarine canyons, but their origin is basically tectonic. Submarine canyons are widely found on ocean floors throughout the world. Along the shores of the USSR, large submarine canyons are encountered in the Black Sea, the seas bordering the Far East, and the Arctic Ocean.