Sand dunes are created when wind deposits sand on top of each other until a small mound starts to form. Once that first mound forms, sand piles up on the windward side more and more until the edge of the dune collapses under its own weight.
Types of Dune Formations
Sand dunes come in many different shapes, and the type of dune is determined by the wind direction, sand type, and environment. The five main types of sand dunes are:
Barchan or crescentic-shaped dunes
The most common type of dune, barchans are wider than they are long and have a concave slipface. They form when winds blow from one direction. If barchan dunes become large and connect, they can transform into transverse dunes.
Linear dunes
These dunes form straight or nearly straight lines, and some have a wavy shape. They develop when wind pressures are similar on both sides of the dune.
Star dunes
These dunes have pointed ridges and slipfaces on at least three sides. They form when winds come from multiple directions.
Parabolic dunes
Also known as blowouts, these dunes are similar to crescent-shaped dunes but have a slipface on the inward side. They form when winds blow out the center of the dune, leaving a rim on the outside.
Dome dunes
The rarest type of dune, domes are circular and don't have a slipface.