3. Aeolian Erosion

Erosion by Wind

Wind is also an agent of erosion. It carries dust, sand, and volcanic ash from one place to another. Wind can sometimes blow sand into towering dunes. Some sand dunes in the Badain Jaran area of the Gobi Desert in China reach more than 400 meters (1,300 feet) high.

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In dry areas, windblown sand blasts against rock with tremendous force, slowly wearing away the soft rock. It also polishes rocks and cliffs until they are smooth.

From http://www.ck12.org/

From http://www.ck12.org/

Wind is responsible for the dramatic arches that give Arches National Park, in the U.S. state of Utah, its name. Wind can also erode material until nothing remains at all. Over millions of years, wind and water eroded an entire mountain range in central Australia. Uluru, also known as Ayers Rock, is the only remnant of those mountains.

Wind Erosion

 

Wind is a stronger erosional force in arid regions than it is in humid regions because winds are stronger. In humid areas, water and vegetation bind the soil so it is harder to pick up. In arid regions, small particles are selectively picked up and transported.

 

Deflation

 

As small particles are removed, the ground surface gets lower and rockier, causing deflation . What is left is desert pavement, a surface covered by gravel-sized particles that are not easily moved by wind.

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Desert Pavement, Mojave Desert, California

Desert Pavement, Mojave Desert, California

Abrasion

 

Particles moved by wind do the work of abrasion. As a grain strikes another grain or surface it erodes that surface. Abrasion by wind may polish natural or human-made surfaces, such as buildings. Stones that have become polished and faceted due to abrasion by sand particles are called ventifacts.

The Dry Valleys, Antarctica

The Dry Valleys, Antarctica

 

Desert Varnish

Exposed rocks in desert areas often develop a dark brown or black coating called desert varnish . Wind transports clay-sized particles that chemically react with other substances at high temperatures. The coating is formed of iron and manganese oxides.

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A hunting scene cut into desert varnish by Native Americans in Utah’s Nine Mile Canyon.