Erosion is a natural process.
Erosion and its processes are an essential part of both the natural world and the study of geology. By learning how substances erode, we discover more about them and in doing so, gain a greater understanding of the natural world. Everything falls apart, but if we can observe how and why it does, then we can learn about everything from what building materials are best to survive in inhospitable environments.
Raindrop erosion is caused by the impact of water on the surface of the ground. Sheet water erosion is much more severe, and takes place when the ground cannot absorb more water and the excess moves across the surface in a flood. Finally, rill and gully erosion is caused by water being concentrated into small drainage channels in the soil which swell and eventually cut through the ground at the surface. Left unchecked, these will eventually form larger gullies which will erode still further.
Wind erosion is most common in arid areas and can, in turn, be broken down into two different processes. Deflation is the process where particles are picked up by the wind and carried downwind and away from their point of origin. Abrasion, the second process, is a by-product of this, as the particles impact on, and in doing so erode, other surfaces as they travel past them. Five million acres of land in the United States are damaged by wind erosion every year.
Mass movement, or movement downhill, is the most common type of gravity erosion. The most common form of this is known as surface creep and occurs very gradually. Large-scale mass movement is often referred to as a landslide. Slumping, the other primary form of gravity erosion, takes place when a substance fractures along a particular line and moves rapidly downhill. This is common in clay or clay-based soils.
Other Types of Erosion
Glacial erosion is caused by the movement of glaciers across the surface of the Earth, carving the ground beneath and around them as they go. Shoreline erosion takes several forms, and is caused by the tidal action of the sea eroding the rocks of the shoreline. One of the most notable forms of this is when hydraulic action fills a joint in rock with water, eroding it. Finally, thermal erosion is caused by the weakening of permafrost by moving water. This occurs most notably on the Arctic coast where temperature and wave motion combine to erode the base of coastal permafrost bluffs.