Generally, sand dunes in nature are small hills or ridges accumulated by wind, which are common on the coast, some river valleys, and some dry sand surfaces in the dry season. The existence of sand dunes is caused by the unconsolidated material moved by wind.

Sand dunes are usually associated with desert areas where wind-blown sand occupies a large area. For example, in the Sahara Desert, sand deposits account for about 7million square kilometers.

Sand dunes are moving hills. They move in two ways.

First, through the process of bouncing, the wind blows up the sand particles, moves them for a certain distance, and then falls. When sand scrapes over a stony surface, the sand particles may bounce several meters high, otherwise they move only a few centimeters high on the ground surface.

Second, the bouncing sand particles collide with the ground again and push other sand particles forward with the help of the impact force. This movement is called surface creep.