landform, hill of sand

In physical geography, a dune is a hill or ridge of sand, usually deposited by eolian processes (wind) or sometimes by the flow of water. Dune fields cover large parts of some deserts, and some beaches have dunes. Mars has many dunes. Sand dunes have different forms and sizes based on their interaction with the wind. Sometimes they migrate downwind.

Mesquite Sand Dunes - Death Valley California