Aeolian processes

Aeolian processes, also spelled eolian, pertain to wind activity in the study of geology and weather and specifically to the wind's ability to shape the surface of the Earth (or other planets). Winds may erode, transport, and deposit materials and are effective agents in regions with sparse vegetation, a lack of soil moisture and a large supply of unconsolidated sediments. Although water is a much more powerful eroding force than wind, aeolian processes are important in arid environments such as deserts. The term is derived from the name of the Greek god Aeolus, the keeper of the winds. Aeolian processes are those processes of erosion, transport, and deposition of sediments that are caused by wind at or near the surface of the earth. Sediment deposits produced by the action of wind and the sedimentary structures characteristic of these deposits are also described as aeolian. Aeolian processes are most important in areas where there is little or no vegetation. However, aeolian deposits are not restricted to arid climates. They are also seen along shorelines; along stream courses in semiarid climates; in areas of ample sand weathered from weakly cemented sandstone outcrops; and in areas of glacial outwash. Loess, which is silt deposited by wind, is common in humid to subhumid climates. Much of North America and Europe are underlain by sand and loess of Pleistocene age originating from glacial outwash. The lee (downwind) side of river valleys in semiarid regions are often blanketed with sand and sand dunes. Examples in North America include the Platte, Arkansas, and Missouri Rivers. Wind erodes the Earth's surface by deflation (the removal of loose, fine-grained particles by the turbulent action of the wind) and by abrasion (the wearing down of surfaces by the grinding action and sandblasting by windborne particles). Once entrained in the wind, collisions between particles further break them down, a process called attrition. Worldwide, erosion by water is more important than erosion by wind, but wind erosion is important in semiarid and arid regions.