The Atacama Desert is a plateau in South America, covering a strip of land on the Pacific coast, west of the Andes mountains. It is the driest non-polar desert in the world. According to estimates the Atacama Desert proper occupies , or if the barren lower slopes of the Andes are included. Most of the desert is composed of stony terrain, salt lakes (salares), sand, and felsic lava that flows towards the Andes.