The Atacama Desert is a high desert plateau in South America covering a 1,600 km (990 mi) strip of land on the Pacific coast, west of the Andes Mountains running through Northern Chile and Souther Western Peru. The Atacama Desert is the driest nonpolar desert in the world, and the only true desert to receive less precipitation than the polar deserts and the largest fog desert in the world. Both regions have been used as experimentation sites on Earth for Mars expedition simulations. According to estimates, the Atacama Desert occupies 105,000 km2 (41,000 sq mi) which makes it about the size of Virginia, or 128,000 km2 (49,000 sq mi) if the barren lower slopes of the Andes are included. Most of the desert is composed of stony terrain, salt flats, sand, and felsic lava that flows towards the Andes. Perhaps this starkly beautiful area has become so famous as of late is because of the construction of a number of huge telescopes of every type and size especially the ELT from my book and the neighboring VLT less than 20 miles away to the west of the ELT. There are several radio telescopes located in and around the Atacama Desert as well such as ALMA and the ASTE just north of the ELT.
The desert owes its extreme aridity to a constant temperature inversion because of the cool north-flowing Humboldt ocean current and to the strong Pacific anticyclone. The most arid region of the Atacama Desert is between two mountain chains (the Andes and the Chilean Coast Range) of sufficient height to prevent moisture advection from either the Pacific or the Atlantic Ocean, a two-sided rain shadow.
Despite modern views of Atacama Desert as fully devoid of vegetation in pre-Hispanic and Colonial times, a large flatland area known as Pampa del Tamarugal was forested, with demand of firewood associated silver and saltpeter mining causing widespread deforestation in the 18th and 19th centuries.
According to the World Wide Fund for Nature, the Atacama Desert ecoregion occupies a narrow strip of coastal plateau, arid coastal mountains and a portion of the Andean Foothills of the northern third of Chile, from near the town of Arica (18°24′S) southward to La Serena (29°55′S). The National Geographic Society considers the coastal area of southern Peru to be part of the Atacama Desert and includes the deserts south of the Ica Region in Peru.
Peru borders it on the north and the Chilean Matorral ecoregion borders it on the south. To the east lies the less arid Central Andean dry puna ecoregion. The drier portion of this ecoregion is located south of the Loa River between the parallel Sierra Vicuña Mackenna and Cordillera Domeyko. To the north of the Loa lies the Pampa del Tamarugal.
The magnificent Coastal Cliffs of northern Chile just west of the Chilean Coast Range is one of the main topographical features of the north coast of Chile especially the region just north of Antofagasta. The geomorphology of the Atacama Desert has been characterized as a low-relief bench “similar to a giant uplifted terrace”. The intermediate depression (or Central Valley) forms a series of endorheic basins in much of the Atacama Desert, south of latitude 19°30’S. North of this latitude, the intermediate depression drains into the Pacific Ocean.
On 25 March 2015, heavy rainfall affected the southern part of the Atacama Desert. Resulting in catestrophic floods triggering mudflows that affected the cities of Copiapo, Tierra Amarilla, Chanaral, and Diego de Almagro, causing the deaths of more than 100 people.
The Atacama Desert is commonly known as the driest nonpolar place in the world, especially the surroundings of the abandoned Yungay town (in Antofagasta Region, Chile). The average rainfall is about 15 mm (0.6 in) per year, although some locations receive 1 to 3 mm (0.04 to 0.12 in) in a year. Moreover, some weather stations in the Atacama have never received rain. Periods up to four years have been registered with no rainfall in the central sector, delimited by the cities of Antofagasta, Calama, and Copiapó, in Chile. Evidence suggests that the Atacama may not have had any significant rainfall from 1570 to 1971.
The Atacama Desert may be the oldest desert on earth, and has experienced extreme hyperaridity for at least 3 million years, making it the oldest continuously arid region on earth. The long history of aridity raises the possibility that supergene mineralisation, under the appropriate conditions, can form in arid environments, instead of requiring humid conditions. The presence of evaporite formations suggest that in some sections of the Atacama Desert, arid conditions have persisted for the last 200 million years (since the Triassic).
The Atacama is so arid that many mountains higher than 6,000 meters (20,000 ft) are completely free of glaciers. Only the highest peaks (such as Ojos del Salado, Monte Pissis, and Llullaillaco) have some permanent snow coverage.
The southern part of the desert, between 25 and 27°S, may have been glacier-free throughout the Quaternary (including during glaciations), 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. However, some locations in the Atacama receive a marine fog known locally as the camanchaca, providing sufficient moisture for hypolithic algae, lichens, and even some cacti—the genus Copiapoa is notable among these.
Geographically, the aridity of the Atacama is explained by it being between two mountain chains (the Andes and the Chilean Coast Range) of sufficient height to prevent moisture advection from either the Pacific or the Atlantic Oceans, a two-sided rain shadow.