Winds also form thick clouds of sand. These clouds of sand look like huge dark waves and block out the sun, acting like a thick fog. The winds swirl about catching sand, and form columns called dust devils . Over time, when all the sand is blown away from the area, it leaves behind only rocks. In polar deserts , snow dunes occur commonly in areas where precipitation is locally more abundant.
Temperatures change frequently, crossing the freezing point of water.
This freeze-thaw alternation forms patterned textures on the ground.