Sand covers less than 20% of the earth’s surface, but they are what pops into most
people’s minds when one mentions the desert. There are three basic forms of the popular
sand dune, and each one is shaped by the topography of the land and wind flow patterns.
For example, the sand dunes of inner Australia are often linearly shaped. Because they
are aligned with strong winds, they look like furrows from high in the air. Another type
of sand structure are crescent dunes, also known by the Russian name, barchan. These
sickle-shaped U’s and V’s are symmetrically shaped mounds that move across the desert
as much as fifty feet per year. The final type of dune is most troublesome to desert
travelers. Closely packed and formed by shifting winds, they resemble curling starfish
with high heaps of sand at the center. Some of these grow higher than 1,500 feet.