The Earth Science Encyclopedia: Wind Erosion and Deposition
May 12, 2019
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A short information on the erosion and deposition activity of wind intended to shed light on how these aeolian processes work to form various landforms on the surface of the Earth. Continue reading...
The erosion of landforms by wind, transportation of eroded material and its deposition are the three attributes of wind activity which facilitate the formation of various landforms on this planet. These three attributes are referred to as the aeolian processes - a term derived from the name of the Greek God of wind 'Aeolus'.
As with various other agents of erosion, even wind plays a crucial role in shaping the surface of our planet by eroding various landforms, transporting this eroded material and depositing it to other places. Some examples of landforms created by the erosional and deposition activity of wind are yardang, deflation hollows, pans, sand dunes, etc.
Aeolian Processes: Wind Erosion, Transportation and Deposition
As with various other types of erosion, even wind erosion - aka aeolian erosion, revolves around detachment, transportation and deposition of soil particles. Wind erosion is most prominent in regions wherein vegetation cover is pretty sparse, and rainfall in minimal.
That explains why you get to see very obvious effects of wind erosion in dry, arid regions of the world, wherein wind velocity is very high as there are no trees to obstruct the flow. There exist two methods by which wind carries out its erosional activity on the Earth's surface - deflation and abrasion. Here are the details of each of these methods.
★ Deflation: In geology, deflation refers to erosive action of wind wherein it lifts loose soil particles off the ground and transports them from one place to another. This method of wind erosion is most prominent in deserts, wherein sand particles are lifted by wind and transported to other parts of the desert to form large sand dunes.
★ Abrasion: When tiny particles of soil which are suspended in the air are blasted against a standing structure, the standing structure begins to erode over the course of time.
This process by which wind erodes various landforms - and results in formation of structures like mushroom rock, is referred to as abrasion. (When the particles which hit a standing structure break into tiny fragments, it is referred to as attrition.)
These fine particles are then carried by wind to considerable distance depending on what the velocity of wind and the size of particles is. The transportation of these particles is categorized into three different methods suspension, saltation and creeping. Here are the details of each of these methods.
★ Suspension: When the diameter of soil particles is 0.1 mm or less, these particles tend to stay suspended in the air and wind carries them along for considerable distance - at times exceeding thousands of miles. This mode of transportation of eroded material by wind is referred to as suspension method.
★ Saltation: When the diameter of soil particles is roughly between 0.1 mm and 0.5 mm, they are too heavy to be transported over considerable distance. In such situation, these particles are lifted and deposited at a short distance, and continuous repetition of this method - which is referred to as saltation, transports them to a considerable distance.
★ Creeping: When the diameter of soil particles is 0.5 mm or more, it becomes difficult for the wind to lift them and therefore they are transported by wind from one place to another by rolling them along the ground. This method by which wind transports eroded material is referred to as creeping.
The last of the aeolian processes is that of deposition, wherein all the eroded material is deposited by the wind. As with the erosional activity, even the deposition activity of the wind is governed by its velocity. More the speed of the wind, more amount of soil particles can it carry.
As its speed slows down eventually - as a result of change in the pattern of landforms pr presence of vegetation, wind starts depositing the eroded material on the ground. Heavy particles are dropped first, while light particles are transported further and deposited when wind speed decreases by a significant extent.
While yardang, blowouts, ventifacts, mushroom rocks, hoodoos, etc., happen to be landforms created by wind erosion, the deposition of this eroded material results in formation of sand sheets, sand dunes, sand hills, loess, paha, ergs, etc.
While water as an agent of erosion is way more powerful as compared to wind when it comes to regions which experience a significant amount of rainfall, it is wind that is the lone powerful force when it comes to arid landscapes devoid of water.
However, that doesn't mean wind erosion and deposition only takes place in deserts and other arid regions. Even coastal areas - with wind blowing over the ocean at a considerable speed, are vulnerable to aeolian processes with several beaches and sea cliffs of the world showing the traces of the same.