Dunes

desert · geology · wind

Sand shaped by wind. Dunes form when wind pushes sand into mounds, ridges, and hills. The side facing the wind (called the stoss side) is longer and gentler, while the side sheltered from the wind has a steep drop called the slip face.

Water makes dunes too. While wind is the most famous dune builder, water currents and waves can also pile up sand into dune shapes, especially along beaches and underwater.

Dunes have names. A giant area covered in lots of dunes is called a dune field or erg, and the valleys between dunes are called dune slacks. Some ergs are as big as countries.

Dunes come in shapes. Dunes can look like simple hills, long ridges, stars, or crescents. The shape depends on the direction and strength of the wind and how much sand is available.

Life in the dunes. Some dunes have almost no plants and are called sand seas, but other dunes can support hardy desert plants and animals that are specially adapted to sandy life.