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|barchan dune |
A large, crescent-shaped dune lying at right angles to the prevailing wind and having a steep, concave leeward side with the crescent tips pointing downwind. Barchan dunes form on flat, hard surfaces where the sand supply is limited. They can reach heights of up to 30 m (98 ft) and widths of 350 m (1,148 ft). See illustration at dune.