microorganisms in soil that will promote the acidity needed for chemical weathering. •
Exposure time is important too. The longer an area is exposed to any weathering process, the more likely it is to be affected by the process.
So, when we think of weathering, we often think of things like wind, but chemistry and water often have more to do with weathering than wind. Still, wind does play a role in erosion and weathering.
WIND AND DESERT FEATURES Weathering can happen in a desert just as much as in wetter climates. It just happens at a much slower rate. You need water to have legitimate weathering. Without water, you'll get mechanical weathering as the main part of this process. You also won't get much runoff without water. Desert varnish is a unique weathering feature seen in deserts, for example. It is a thin brown layer of clay minerals from manganese and iron oxides found in dry environments where oxides form but don't wash away. Fine sand that flows due to saltation is a main force for mechanical weathering in a desert. Saltation is essentially the bouncing of small grains along a surface. This saltation zone sandblasts many unique features in the desert. If winds are severe, you might get a blowout, which is a depression left over after materials have gotten blown out by the wind. Some desert features you might see are these: •
Playa – these are dry evaporated lake beds where streams ran in and left water behind.
•
Ephemeral streams – these are areas that are streams only if there are heavy rains. Flash floods can come from these areas that just don't drain quickly.
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Sand dunes – these are deposits of sand created by shifting winds and variations in sand supply or the addition of vegetation in some areas but not others.
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