Erosion, Level of

(in Russian, bazis erozii), the level of a basin into which a stream of water empties. The general (or main) level of erosion is the level of the world ocean. The local (or temporary) level of erosion is that of flowing lakes, places where tributaries empty into the main river, and outcrops of solid rock that slow subsurface erosion of a river and that cause rapids to be formed. Changes in the height of the level of erosion (fluctuations of the sea level, secular movements of the earth’s crust) are followed by the cutting of a valley or by its becoming filled with river deposits.