Dune

A dune is a landform built up from loose sand that has been shaped by wind or, in some settings, by the flow of water. It typically takes the form of a mound, ridge, or hill, and dunes commonly cluster into a dune system or dune field. A broad, largely bare region covered in wind driven sand is called an erg or sand sea. Most dunes are asymmetrical, rising gradually on the upwind, or stoss, side where sand is pushed upward, then dropping more steeply on the downwind slip face. The low ground between two dunes is known as a dune slack.