The Atacama Desert (Spanish: Desierto de Atacama) is a plateau in South America, covering a 1,000-kilometre (600 mi) 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 105,000 square kilometres (41,000 sq mi), but its size rises to 128,000 square kilometres (49,000 sq mi) when 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 flows towards the Andes.
The World Wide Fund for Nature defines the Atacama Desert ecoregion as extending from a few kilometers south of the Peru–Chile border to about 30° south latitude. The National Geographic Society considers the coastal area of southern Peru to be part of the Atacama Desert and also includes the deserts south of the Ica Region in Peru.
The Peruvian Sechura Desert ecoregion 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 Atacama Desert is commonly known as the driest place in the world, especially the surroundings of the abandoned Yungay town (in Antofagasta Region, Chile). The average rainfall is about 15 millimetres (0.59 in) per year, although some locations, such as Arica and Iquique receive 1 millimetre (0.04 in) to 3 millimetres (0.12 in) in a year. Moreover, some weather stations in the Atacama have never received rain. Periods of 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 Desert is probably also 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. Geological research suggests that in some sections of the Atacama Desert, such as in today’s Chile, hyperaridity has persisted for the last 200 million years (since the Triassic).
This desert is so arid that many mountains higher than 6,000 metres (20,000 ft) are completely free of glaciers; indeed, only the highest peaks (such as Ojos del Salado, Pissis, and Llullaillaco) have some permanent snow coverage. The southern part of the desert, between 25°S to 27°S, may have been glacier-free throughout the Quaternary (including during glaciations), though permafrost extends down to an altitude of 4,400 metres (14,400 ft) and is continuous above 5,600 metres (18,400 ft). Studies by a group of British scientists have suggested that some river beds have been dry for 120,000 years, the same amount as Chad’s drought. 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 situated 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.
Although the almost total lack of precipitation is the most prominent characteristic of the Atacama Desert, exceptions may occur. In July 2011, an extreme Antarctic cold front broke through the rain shadow, bringing 80 centimetres (31 in) of snow to the plateau, stranding residents across the region, particularly in Bolivia, where many drivers became stuck in snow drifts and emergency crews became overtaxed with a large number of rescue calls.
This phenomenon is called the altiplano winter, which can produce a little rain and abundant electrical storms, and occurs in January and February. In 2012, the altiplano winter brought floods to San Pedro de Atacama.
In a region about 100 kilometres (60 mi) south of Antofagasta, which averages 3,000 metres (10,000 ft) height, the soil has been compared to that of Mars. Owing to its otherworldly appearance, the Atacama has been used as a location for filming Mars scenes, most notably in the television series Space Odyssey: Voyage To The Planets.
In 2003, a team of researchers published a report in the journal Science 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. The team duplicated the Viking tests in Mars-like Earth environments and found that they missed present signs of life in soil samples from Antarctic dry valleys, the Atacama Desert of Chile and Peru, and other locales.
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.
In 2008, the Phoenix Mars Lander detected perchlorates on the surface of Mars at the same site where water was first discovered. Perchlorates are also found in the Atacama and associated nitrate deposits have contained organics, leading to speculation that signs of life on Mars are not incompatible with perchlorates. The Atacama is also a testing site for the NASA-funded Earth-Mars Cave Detection Program.
The Valle de la Luna in English, the Valley of the Moon, is another area of the Atacama Desert which is said to look like the surface of the moon. It lies 13 kilometres (8 mi) to the west of the town, San Pedro de Atacama.
In spite of the geographic and climatic conditions of the desert, a rich variety of flora has evolved here. Over 500 species have been gathered within the border of this desert. These species are characterized by their extraordinary ability to adapt to this extreme environment. Most common species are the herbs and flowers such as thyme, llareta and saltgrass (Distichlis spicata) and, where humidity is sufficient, trees such as the chañar (Geoffroea decorticans), the pimiento tree and the leafy algarrobo (Prosopis chilensis).
The llareta is one of the highest-growing wood species in the world. It is found at altitudes between 3,000 meters (9,842 feet) and 5,000 meters (16,404 feet). Its dense form is similar to a pillow some 3 to 4 meters (10 to 13 feet) thick. It concentrates and retains the heat from the day in order to cope with low evening temperatures. The growth rate of the llareta has been recently estimated at approximately 1.5 centimeters per year, making many llaretas over 3,000 years old. It produces a much-prized resin, which the mining industry once harvested indiscriminately as fuel, making this plant endangered.
The desert is also home to cacti, succulents and other plants that thrive in a dry climate. Cactus species here include the candelabro (Browningia candelaris) and cardon (Echinopsis atacamensis), which can reach a height of 7 meters (23 feet) and a diameter of 70 centimeters (27 inches).
The Atacama Desert flowering (Spanish: Desierto florido) can be seen in years with sufficient precipitation from September to November.
The climate of the Atacama Desert limits the number of animals living permanently in this extreme ecosystem. Some parts of the desert are so arid that no plant or animal life can survive. Outside of these extreme areas, sand-colored grasshoppers blend with pebbles on the desert floor, and beetles and their larvae provide a valuable food source in the lomas. Desert wasps and butterflies can be found during the warm and humid season, especially on the lomas. Red scorpions also live in the desert.
A unique environment is provided by some small hills (lomas), where the fog from the ocean provides enough moisture for seasonal plants and a few animal species. Surprisingly few reptile species inhabit the desert and even fewer amphibian species. Chaunus atacamensis, the Vallenar toad or Atacama toad, lives on the lomas, where it lays eggs in permanent ponds or streams. Iguanas and lava lizards inhabit parts of the desert, while salt flat lizards, Liolaemus, live in the dry areas bordering the ocean. One species, Liolaemus fabiani, is endemic to the Salar de Atacama, the Atacama salt flat.
Birds are probably the largest animal group in the Atacama. Humboldt penguins live year-round along the coast, nesting in desert cliffs overlooking the ocean. On salt flats both near the Pacific and inland, Andean flamingos flock to eat algae. Other birds (including species of hummingbirds and sparrows) visit the lomas seasonally to feed on insects, nectar, seeds and flowers. The lomas help sustain several threatened species, such as the endangered Chilean woodstar.
Because of the desert’s extreme aridity, only a few specially adapted mammal species live in the Atacama, such as Darwin’s leaf-eared mouse. The less arid parts of the desert are inhabited by the South American gray fox and the viscacha (a relative of the chinchilla). Larger animals, such as guanacos and vicunas graze in areas where grass grows, mainly because it’s seasonally irrigated by melted snow. Vicunas need to remain near a steady water supply, while guanacos can roam into more arid areas and survive longer without fresh water. Seals and sea lions often gather along the coast.
The Atacama is sparsely populated, with most towns located along the Pacific coast. In interior areas, oases and some valleys have been populated for millennia and were the location of the most advanced Pre-Columbian societies found in Chile. These oases have experienced little population growth and urban development. During the 20th century they have had conflicts over water resources with the coastal cities and the mining industry.
San Pedro de Atacama, at about 2,000 metres (7,000 ft) elevation, is like many of the small towns. Before the Inca empire and prior to the arrival of the Spanish, the extremely arid interior was inhabited primarily by the Atacameño tribe. They are noted for building fortified towns called pucarás, one of which is located a few kilometers from San Pedro de Atacama. The town’s church was built by the Spanish in 1577.
The coastal cities originated in the 16th, 17th, and 18th centuries during the time of the Spanish Empire, when they emerged as shipping ports for silver produced in Potosí and other mining centers. During the 19th century the desert came under control of Bolivia, Chile, and Peru. With the discovery of sodium nitrate deposits and as a result of unclear borders the area soon became a zone of conflict and resulted in the War of the Pacific. Chile annexed most of the desert, and cities along the coast developed into international ports, hosting many Chilean workers who migrated there.
With the guano and saltpeter booms of the 19th century the population grew immensely, mostly as a result of immigration from central Chile. In the 20th century the nitrate industry declined and at the same time the largely male population of the desert became increasingly problematic for the Chilean state. Mineworkers and mining companies came into conflict, and protests spread throughout the region.
The Atacama Desert again became a source of wealth from the 1950s onwards, owing to copper mining. The Escondida and Chuquicamata porphyry copper mines are located within the Atacama Desert.
Inhabited towns in the desert include San Pedro de Atacama, Vallenar, and Freirina. In San Pedro de Atacama there is a marketplace for artisanal goods.
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 and resulted in The War in the Pacific.
The desert is littered with approximately 170 abandoned nitrate (or “saltpetre”) mining towns, almost all of which were shut down decades after the invention of synthetic nitrate in Germany at the turn of the 20th century (see Haber process). The towns include Chacabuco, Humberstone, Santa Laura, Pedro de Valdivia, Puelma, María Elena, and Oficina Anita.
The Atacama Desert is rich in metallic mineral resources such as copper, gold, silver and iron as well as non metallic minerals including important deposits of boron, lithium, sodium nitrate and potassium salts. The Salar de Atacama is a place where bischofite is extracted. These resources are exploited by various mining companies such as Codelco, Lomas Bayas, Mantos Blancos, and Soquimich.
Because of its high altitude, nearly non-existent cloud cover, dry air, and lack of light pollution and radio interference from the very widely spaced cities, this desert is one of the best places in the world to conduct astronomical observations. The European Southern Observatory operates two major observatories in the Atacama:
A new radio astronomy telescope, called ALMA, built by Europe, Japan, the United States, Canada and Chile in the Llano de Chajnantor Observatory officially opened on 3 October 2011. A number of radio astronomy projects, such as the CBI, the ASTE and the ACT, among others, have been operating in the Chajnantor area since 1999.