The Atacama Desert is a plateau in South America, covering a 600-mile (1,000 km) strip of land on the Pacific coast of South America, west of the Andes mountains. The Atacama desert is, according to NASA, National Geographic and many other publications, the driest desert in the world, due to the rain shadow on the leeward side of the Chilean Coast Range, as well as a coastal inversion layer created by the cold offshore Humboldt Current.
The Atacama occupies 40,600 square miles (105,000 km2) in northern Chile, composed mostly of salt basins (salaries), sand, and felsic lava flows towards the Andes. More than 5,000 geoglyphs—prehistoric works of art placed on or worked into the landscape—have been recorded in the Atacama Desert of northern Chile over the past thirty years. Using artifacts and stylistic characteristics, archaeologists believe the earliest was first constructed during the Middle Period, beginning around 800 AD.
The most recent may be associated with early Christian rites in the 16th century. Some geoglyphs are found in isolation, some are in panels of up to 50 figures. They are found on hillsides, pampas, and valley floors throughout the Atacama Desert; but they are always found near ancient pre-Hispanic trackways marking llama caravan routes through the difficult regions of the desert connecting the ancient people of South America. Coastal inversion layer created by the cold Humboldt Current and the anticyclone of the Pacific is essential to keeping the climate of the Atacama dry.
The average rainfall in the Chilean region of Antofagasta is just 1 millimeter (0.04 in) per year. Some weather stations in the Atacama have never received rain. Evidence suggests that the Atacama may not have had any significant rainfall from 1570 to 1971. It is so arid that mountains that reach as high as 6,885 meters (22,589 ft) are completely free of glaciers and, in the southern part from 25°S to 27°S, may have been glacier-free throughout the Quaternary, though permafrost extends down to an altitude of 4,400 meters (14,400 ft) and is continuous above 5,600 meters (18,400 ft). Studies by a group of British scientists have suggested that some river beds have been dry for 120,000 years. The desert has rich deposits of copper and other minerals, and the world’s largest natural supply of sodium nitrate, which was mined on a large scale until the early 1940s. The Atacama border dispute over these resources between Chile and Bolivia began in the 19th century.
One important image is the stepped rhombus, essentially a staircase shape of stacked rhomboids or diamond shapes (such as in the figure). The Atacama Desert ecoregion, as defined by the Worldwide Fund for Nature (WWF), extends from a few kilometers south of the Peru-Chile border to about 30° south latitude. To the north lies the Sechura Desert ecoregion, in Peru, whilst to the south is the Chilean Matorral ecoregion.