The simplest and the most well-known dune is the barchan dune. The barchan dune is a crescent-shaped dune usually located in desert climates. The arms or "horns" of the dune point downwind, and move faster than the center of the dune.

Barchan dunes have a ten to one ratio of width to height. Their relatively small size allows for barchan dunes to move between 8 and 12 feet per year. When enough sand is present, barchan dunes coalesce into what is known as barchanoid ridges. If these dunes continue to develop they can eventually form transverse dunes.

Barchan dune at White Sands National Monument, New Mexico. (Photo by Keene Swett. University of Iowa Geosciences Slides Collection)

These dunes form when there is a hard, flat landscape with wind flowing in one direction, very sparse vegetation and a limited sand supply. But these conditions are rarely found, even in desert environments making this a rather uncommon dune. In fact, barchan dunes only comprise a small percentage of the world's dunes.

In the United States, barchan dunes can be found in deserts such as White Sand Dunes National Monument (New Mexico)and Great Sand Dunes National Park (Colorado).