Base level of erosion

BASE LEVEL OF EROSION (EN: base level of erosion; DE: Erosionsbasis; FR: base de l'érosion; ES: nivel de base de erosion; RU: базис эрозии) is the surface of the longitudinal profile of the water flow, at the level of which the flow (river, brook) loses its energy, and below which it can not deepen (erode) its bed. The general (main) base level of erosion is the level of the world ocean, or more precisely, the level of the bottom of the water streams, which are flowing into it, within their mouth. For the rivers, which end blindly within the inland depressions, there plays the same role the level of the non-draining lake, which is situated within the depression, or, if the depression is dry, the level of the bottom of the depression itself. Upstream along the water flow, there may be situated the local base levels of erosion, which are limiting the depth of the erosion at the individual places of its longitudinal profile; there may serve as these local levels the level of the draining lakes, or the outcrop onto the surface of the solid, hard to erode argillaceous rocks. For the tributaries, there serves as the base level of erosion the level of the water of the main water flow at the place of their confluence. The shanges of the height of the base level of erosion, namely, absolute (fluctuations of the level of ocean) and relative (oscillatory movements of the Earth's crust), cause the amplification or attenuation of the erosion, and are one of the causes for the change of the phases of the incision of the rivers, for the deepening of their valleys, and for the filling of these valleys by the fluvial depositions.

V. E. Shantser.