Sand Dunes

Dune types A barchan (pronounced bar-KAN) dune, sometimes known as a crescentic dune, is a crescent or U-shaped dune that has its “horns” or tips pointing downwind or away from the wind. Barchans arise where sand supply is limited, where the ground is hard, and where wind direction is fairly constant. They form around shrubs or larger rocks, which act as anchors to hold the main part of the dune in place while the tips migrate with the wind. Barchan dunes occur widely in deserts around Earth.