Black Earth

Black Earth (Tchernozem of Russian geologists) is the name given to a deposit which covers vast areas in South Russia, extending over the steppes and low-lying plateaus that border on the Black Sea, and the depressed area to the north of the Caspian, with a breadth from north to south of from 200 or 300 to nearly 700 miles. It closely resembles the Löss (q.v.) of Central Europe in texture and structure, for it is fine grained, and is usually devoid of stratification. It varies in colour, however, from dark brown to black, and in thickness from a foot or two up to 6 or 7 yards, occasionally reaching, it is said, even to 60 feet. It is composed chiefly of siliceous sand (about 70 per cent.), alumina and other ingredients (23 per cent.), and organic matter (about 7 per cent.). But the composition is variable, the organic matter sometimes exceeding 10 per cent. It appears to be unfossiliferous. It bears the same relation to the glacial accumulations of Russia that the löss of the Rhine, the Danube, &c. does to those of Central Europe, and is probably the fine-grained silt derived from the torrents and flooded rivers that escaped from the melting snows and glaciers of the glacial period. According to some geologists, however, it may owe its origin to the action of the wind. It is supposed by them to be simply an accumulation of wind-blown dust—the finely sifted material being fixed by the abundant grasses of those steppe regions.