Erosion

Abstract

Erosion is the movement of material from rest, as opposed to sediment transport, which is the ongoing movement of material, and deposition, which is the cessation of movement. The topics covered pertain to erosion of the land surface and related processes. It does not include subsurface movement of material that may occur by processes of dissolution or piping or subaqueous erosion may occur at the bottom of lakes and seas. The word “erosion” immediately conjures up a vast literature concerned with soil erosion, but it also refers to the movement of geologic materials in geomorphic systems such as rivers, dunes, beaches, glaciers, and landslides. Surface erosion may be caused by a variety of physical processes including water (fluvial erosion), wind (aeolian erosion or deflation), waves and tides (coastal erosion), ice (glacial erosion and nivation), gravitational failures (mass movement), and human movement of materials (anthropogenic erosion). The latter topic may be distinguished as accelerated as opposed to natural erosion. A broad view of erosion is important for many reasons including threats of property damage and public safety by geomorphic processes, chemical changes such as sequestration or release of carbon and toxins, and off-site damages of sedimentation. Studies of erosion covered in this article are grouped into two fundamental classes: soil erosion and geomorphic erosion. The first group of topics is concerned with soil erosion and includes agricultural sustainability, soil conservation, soil erosion processes, modeling soil erosion, and gully erosion. Much of the scientific literature on soil erosion has focused on (1) arable land because of the importance of soils to global food production or (2) other lands because of the ecosystem services that soils provide and the off-site costs of sediment. Erosion includes the removal of rock, beach, channel, and other geologic materials in addition to soils. Studies of erosion of these geologic materials are grouped by the various geomorphic systems in which they occur (e.g., channel erosion, aeolian [wind] erosion, coastal erosion [waves and tides], glacial erosion, and mass movements [landslides or gravitational failures]). This review ends with studies of anthropogenic erosion beyond the erosion of soil and geomorphic systems, such as mining and construction, and the effects of erosion on the global carbon budget and climate change. This article does not cover the large scientific literature on long-term denudation or landscape evolution studies, the history of soil erosion, or erosion following natural disturbances such as fire and pestilence. Nor does it attempt to cover the numerous regional studies of erosion or benefits of specific soil-conservation techniques. Nevertheless, a broad approach is taken to examine the erosion of soil and geologic materials in response to natural and anthropogenic processes.