Transverse Dunes: wave-like ridges of sand perpendicular to the predominant wind direction. Form in areas of abundant sand supply, scarce vegetation, and moderate, unidirectional winds. They are found not only in deserts, but also behind beaches and on barrier islands.

Longitudinal Dunes: long, narrow ridges of sand parallel to the prevailing wind direction.  They form where sand supply and vegetation are meager and winds are strong. Although they parallel the prevailing wind direction, the slip face varies from one side to the other along the axis of the dune, reflecting variations in wind direction.

Parabolic Dunes: Crescent-shaped with the steep slip face on the convex side so that the “horns” point upwind.  They typically develop where vegetation is available to anchor the horns. In many, the area in front of the dune (between the horns) is a blowout, a small depression excavated by the wind.

Barchan Dunes: crescent-shaped, like parabolic dunes, but the steep slip face is on the concave side – the horns point downwind. Typically develop on barren desert floors where prevailing wind direction is constant, vegetation is scarce, and sand supply is low.  Can occur singly or in groups, where they may join to form more complex shapes.