Desert Pavement

Geology

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Desert Pavement

The surface of the desert floor is very commonly a stony desert pavement, not sand. There are at least two different explanations of why this is so. The usual one is that the wind blows away the finest material, leaving the bigger particles behind as a lag deposit. But another theory is that various physical processes in the soil move the fine particles down beneath the pebbles and cobbles, so that the stones always stay on top. Evidence can be found for both mechanisms, and the precise explanation probably differs from place to place. read more...

Either way, desert pavement serves as a mulch for the plants that live there, and as shelter for the ants and rodents that thrive even in such barren-looking places as this, the Cholla Garden in Joshua Tree National Park, California. more about Joshua Tree...

Notice the dark surfaces of many of the stones. This dark surface is desert varnish. It does not cover every rock because this site is on an alluvial fan, where floodwaters can disturb the surface every few centuries or so.

Here's another example of desert pavement, from the windy floor of crater Gusev on Mars.

_{From NASA image PIA04995_br2.}