Dune

The Atacama Desert is so dry for a number of reasons.

One is its location between two mountain ranges in northern Chile. The peaks of the Chilean Range and the Andes keep storm clouds off the plateau. And there is the wind that blows constantly from east to west drying out an already arid environment. 

It did rain here briefly about two years ago, but there are some weather stations within the Atacama region that have never recorded a drop of rain.

The resulting landscape is mostly rocky with patches of salt flats and other areas covered by sands that have been blowing themselves into dunes for millions of years. In the small town of San Pedro de Atacama, merchants begin each day by sweeping their sidewalks free of the sand that blows in every night and washing them clean with buckets of water. The desert is relentless.