Extreme Landscapes: desert processes

What is a desert?

It is a region with so little vegetation that no significant population can be supported on that land. This implies that it is dry, but not necessarily hot. However, for the purposes of this blog I will consider mid latitude deserts in the interior of continents characterized by low rainfall and high summer temperatures, e.g., Gobi Desert of Mongolia.

The dominant force in a desert is wind. Wind can also cause erosion and deposition in environments where sediments have been recently deposited or disturbed. Erosion by wind is slower than water or ice, but it can move material up and down a slope unlike water. But as the wind velocity increases as does the winds erosive power.

Wind erosion

Removal of loose sediment by the wind. Sediment must be dry. Sand and silt sized material will be moved. Larger material is generally left behind
Abrasion is a physical weathering process. AKA Sand blasting. Impact of windblown particles on exposed surfaces will remove material from that surface
Abrasion will also reduce the size of the particles that are being moved
Generally limited to heights of 1 meter (2 meters max.)

Deposition

In a desert, material moves primarily by the wind through a process called saltation. Deposition occurs in areas where a pocket of slower moving air forms next to much faster moving air. Such pockets typically form behind obstacles like the leeward sides of slopes. As the fast air slides over the calm zone, saltating grains fall out of the air stream and accumulate on the ground surface. (PhysicalGeography.net).

There are different types of sand dunes and desert landforms that i will look at in the next blog. Perhaps to help the students understand the movement of sand we cold look at sand closer to home that is the beach where dunes occur.