Desert pavement occurs where the desert surface has been undisturbed for hundreds, perhaps thousands of years. The surface is composed mostly of rocks, with very little soil between them. If you dig a hole, there will be lots of rocks, but not nearly as concentrated as at the surface.

There are several theories why this occurs. The first two are similar. Wind or rain sweeps away the soil particles between the rocks. The third is called heave, where processes in the ground, such as repeated cycles of wetting and drying, push the rocks to the surface.

You will notice that many of the rocks in the photo are a very dark brown in color. This paper-thin layer is called desert varnish, and occurs when rocks have been exposed on the surface for thousands of years. Manganese-oxidizing bacteria living on the rock surface gradually build up the dark layer.