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Air is a fluid which moves in a course and moves as a consequence of uneven heating of large amounts of air

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Introduction

Introduction Air is a fluid which moves in a course and moves as a consequence of uneven heating of large amounts of air. As the Earth's surface is warmed differentially, the air above the surface absorbs different amounts of heat. Warmer air rises and cool air sinks and this creates the air movement. Winds flow parallel to the latitude, taking heat from equatorial regions to the Polar Regions. SIMPLIFIED: Air near the surface is heated and rises; cooler air comes in to replace hot rising air and this movement of air results in winds. Wind Erosion Erosion by wind is known as Aeolian (or Eolian) erosion and occurs almost always in deserts. Wind erosion will occur when the wind is 30 cm above the ground surface and blows stronger than 12 mph (19.3 km/hr). Dry climates are more vulnerable to wind erosion than humid climates. High wind velocity adds to the wind erosion. Wind erosion occurs mostly in flat, dry areas and moist sandy soils. Wind erosion removes soil and natural vegetation. ...read more.

Middle

Wind Deposition Wind can deposit sediment when its speed decreases so much so that the particles can no longer be transported. This can happen when barriers or obstacles slow the wind speed down. As the air moves over the top of the barrier, wind speed increases. After passing over the barrier the velocity decreases. As the velocity decreases, some of the sediment in suspension can no longer be held, and drops out and gets deposited. Barriers can be such things like rocks, vegetation, and human made structures that jut out above the land surface. Saltation Wind transports sediment near the surface by saltation. Saltation is the short jumps of grains that were loosened from the surface and move in short distances in a jumping motion. As the grains fall back to the surface they may loosen other grains that then get carried by wind until they collide with the ground to loosen other particles. Smaller particles can become suspended in the wind for longer and therefore can travel for longer distances. Saltation moves small particles in the direction of the wind in a series of short hops or skips. ...read more.

Conclusion

Transverse dunes - are large fields of dunes that resemble sand ripples. They consist of folds of sand with a steep face in the downwind side, and form in areas where there is lots of sand and a constant wind direction. Barchan dunes merge into transverse dunes if the amount of sand increases. Linear Dunes - are long straight dunes that form in areas with a small sand supply and converging wind directions. Parabolic (also called blowout) Dunes - are "U" shaped dunes with an open end facing upwind. They are usually fixed by vegetation, and occur where there is plentiful vegetation, a constant wind direction, and a plentiful sand supply. They are common in coastal areas. Star Dunes - are dunes with several arms and many different slip face directions and this form in areas where there is lots of sand and different wind directions. Wind Blown Dust - Dust consists of small sized particles that are often packed together with a smooth surface. The packed dust is difficult to remove by wind erosion, unless the surface is very dry or is disturbed. When dust is disturbed, dust storms can be formed, and dust may be transported by the wind over large distances. ...read more.

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