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For the politico-administrative region of Chile, see Atacama Region.
The Atacama Desert of Chile is a virtually rainless plateau made up of salt basins (salares), sand, and lava flows, extending from the Andes mountains to the Pacific Ocean. It is 15 million years old and 50 times more arid than California's Death Valley.
The average width of the Atacama (east-to-west) is less than 160 kilometers (100 miles) but it extends from the Peruvian border 1000 kilometers (600 miles) south to the Bolivian Altiplano. The mountains nearest to the ocean are the Pacific coastal range, with an average elevation of 800 meters (2500 feet). The Cordillera Domeyko, a range of foothills of the Andes Mountains, lies east.
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Driest Desert
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The Atacama Desert is the driest desert on Earth (with the possible exception of the McMurdo Dry Valleys in Antarctica) and is virtually sterile because it is blocked from moisture on both sides by the Andes mountains and by coastal mountains. The average rainfall in Antofagasta — a region in Chile which is part of the Atacama — is just 1 mm per year, and there was a period of time where no rain fell there for 40 years. It is so arid, in fact, that mountains that reach as high as 6885 metres (22590 feet) are completely free of glaciers and, in the southern part from 25°S to 27°S, have possibly been glacier-free throughout the Quaternary - though permafrost extends down to an altitude of 4400 metres and is continuous above 5600 metres.
Some locations in the Atacama do receive marine fog, providing sufficient moisture for hypolithic algae, lichens and even some cactii. But in the region that is in the "fog shadow" of the high coastal crest-line - the crest-line of the coastal range averages 3000 m for about 100 km south of Antofagasta - the soil has been compared to that of Mars.
In 2003, a team of researchers published a report in Science magazine titled "Mars-like Soils in the Atacama Desert, Chile, and the Dry Limit of Microbial Life" in which they duplicated the tests used by the Viking 1 and Viking 2 Mars landers to detect life, and were unable to detect any signs in Atacama Desert soil. The region may be unique on Earth in this regard and is being used by NASA to test instruments for future Mars missions. Alonso de Ercilla characterized it in La Araucana, published in 1569: "Towards Atacama, near the deserted coast, you see a land without men, where there is not a bird, not a beast, nor a tree, nor any vegetation" (quoted Braudel 1984 p 388).
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Human occupation
The Atacama is inhabited, though sparsely populated. In an oasis, in the middle of the desert, at an altitude of some 2000 meters, is the village of San Pedro de Atacama. Its church was built by the Spanish in 1577, but archeological evidence indicates that the San Pedro area was the center of a Paleolithic civilization that built rock fortresses on the steep mountains encircling the valley. The Escondida Mine and Chuquicamata are also located within the Atacama.
The Atacama 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 between Chile and Bolivia began in the 1800s over these resources.
The Pan-American Highway runs through the Atacama in a north-south trajectory.
The European Southern Observatory operates two major observatories in the Atacama Desert:
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Reference
Braudel, Fernand, The Perspective of the World, vol. III of Civilization and Capitalism 1984 (in French 1979).
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