Also known as corrasion, this is the grinding away of bedrock by fragments of rock which may be incorporated in ice (glacial abrasion), water (marine abrasion, fluvial abrasion), or wind (aeolian abrasion). In fluvial environments, the main agent of abrasion is the bed load. The mass of solid material removed varies with the size, density, and velocity of the particles, and the density of the vector carrying these particles. See Sklar and Dietrich (2004) Water Resour. Res. 40 on a model for bedrock abrasion.