Eolian Processes: The Work of Wind
While water is the dominant agent of erosion globally, in arid and semi-arid regions, the wind is a powerful force for reshaping the landscape. Eolian processes (named after Aeolus, the Greek god of wind) are those associated with the work of the wind.
Wind Erosion
Wind erodes the land in two main ways:
1.Deflation: This is the lifting and removal of loose, fine-grained particles like clay, silt, and sand from the surface. Over time, deflation can lower the entire ground surface, leaving behind coarser, heavier materials. This process is responsible for creating blowouts (depressions) and desert pavement.
Desert Pavement: A surface layer of closely packed, interlocking pebbles and stones left behind after the wind has removed all the finer material. This stony layer then protects the underlying material from further deflation.
2.Abrasion: This process is essentially natural sandblasting. Wind armed with sand particles is a very effective abrasive, capable of polishing, pitting, and etching exposed rock surfaces. Rocks shaped by wind abrasion are called ventifacts.
Wind Transportation
Wind transports sediment in three ways, similar to a river:
Creep: Larger sand grains are rolled along the ground.
Saltation: Sand grains are lifted into the air and bounce along the surface. This is how most sand moves.
Suspension: Very fine dust and silt particles can be lifted high into the atmosphere and carried for very long distances.
Depositional Landforms
When the wind slows down or meets an obstacle, it deposits the sediment it was carrying.
Sand Dunes: These are mounds or ridges of sand deposited by the wind. The shape and size of a dune are controlled by the wind direction, wind speed, and the amount of available sand.
Key characteristics: Dunes have a gentle slope on the windward side and a steep slope (the slip face) on the leeward (downwind) side.
Common types: Barchan (crescent-shaped), Transverse (long ridges perpendicular to the wind), and Longitudinal (long ridges parallel to the wind).
Loess: Extensive blankets of wind-blown silt. The sediment for loess deposits often originates from glacial outwash plains. Loess forms very fertile soil, such as that found in the American Midwest and northern China.