Barchan dunes are crescent-shaped sand dunes with a convex side facing the wind and horns pointing downwind. They form in areas where sand supply is limited, and wind direction is constant. Barchan dunes are significant in the study of desert geomorphology and aeolian processes, providing insights into wind patterns and sediment transport in arid environments.
Reference: Lancaster, N. (1995). Geomorphology of Desert Dunes. Routledge.