Chapter 7.3Landscapes Shaped by Wind

Wind Erosion

• Wind does not erode like water but it is still an important factor in erosion.

• Wind does the most erosional work in deserts.

• Wind erodes in 2 ways: deflation and abrasion.

• Deflation is the lifting and removal of loose particles like clay and silt. Deflation causes blowouts which are depressions in the land. It also causes desert pavement when all the sand and silt is removed and only coarse particles are left.

• Abrasion is when windblown sand cuts and polishes exposed rock surfaces. This can cut large rocks into interesting shapes.

Wind Deposits

• Loess and sand dunes are both features created by wind deposits.

Loess

• Loess is windblown silt that covers the land. There are many loess’ in China.

Sand Dunes

• Sand dunes are mounds or ridges of sand deposited by wind. This occurs usually where the wind encounters an obstruction.

• Dunes will be steeper on the sheltered side and more gently sloped on the side facing the wind.

Types of Sand Dunes

• The form of a sand dune depends on wind direction and speed, how much sand is available, and the amount of vegetation.

Barchan Dunes and Transverse Dunes

• Barchan Dunes are lone sand dunes shaped like crescents. These occur when sand and vegetation are limited.

• Transverse Dunes – where there is plenty of sand and wind and little vegetation the dunes form in a series of long ridges. These are typical in coastal areas.

Barchanoid Dunes and Longitudinal Dunes

• Barchanoid Dunes – This is scalloped rows of sand that are at right angles to the wind.

• Longitudinal Dunes – long ridges of sand that are parallel to the wind. This occurs where wind direction varies.

Parabolic Dunes and Star Dunes

• Parabolic Dunes – The tip points into the wind and are usually along the coast.

• Star Dunes – these are isolated hills of sand found in the Sahara and Arbian deserts.