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. Though there was a general lack of humid air after 33 Ma, there were punctuated intervals of increased humidity, such as between around 10.86 and 6.4 Ma, when the Tiliviche Palaeolake existed before turning into a salar sometime before the Middle Pliocene. The opening of the Tasmania-Antarctic passage allowed for cold currents to move along the west coast of South America, which influenced the availability of warm humid air to travel from the Amazon Basin to the Atacama. The Atacama Desert may be the oldest desert on earth, and has experienced hyper aridity since at least the Middle Miocene, since the establishment of a proto-Humboldt current in conjunction with the opening of the Tasmania-Antarctic passage ca. Evidence suggests that the Atacama may not have had any significant rainfall from 1570 to 1971. 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. Moreover, some weather stations in the Atacama have never received rain. The average rainfall is about 15 mm (0.6 in) per year, although some locations only receive 1 to 3 mm (0.04 to 0.12 in) in a year. The Atacama Desert is commonly known as the driest place in the world, especially the surroundings of the abandoned Yungay mining town, where the University of Antofagasta Desert Research Station is located, in Antofagasta Region, Chile. Aridity A flat area of the Atacama Desert between Antofagasta and Taltal The almost total lack of precipitation is the most prominent characteristic of the Atacama Desert. Climate Snow in Paranal Observatory at 2,600 masl North of this latitude, the intermediate depression drains into the Pacific Ocean. The intermediate depression (or Central Valley) forms a series of endorheic basins in much of the Atacama Desert south of latitude 19☃0'S. The geomorphology of the Atacama Desert has been characterized as a low-relief bench "similar to a giant uplifted terrace" by Armijo and co-workers. The Coastal Cliff of northern Chile west of the Chilean Coast Range is the main topographical feature of the coast. To the north of the Loa lies the Pampa del Tamarugal. The drier portion of this ecoregion is located south of the Loa River between the parallel Sierra Vicuña Mackenna and the Cordillera Domeyko. To the east lies the less arid Central Andean dry Puna ecoregion. Peru borders it on the north and the Chilean Matorral ecoregion borders it on the south. However, other sources consider that the part of the desert in Peru is a different ecosystem, and should properly be named as Pampas de la Joya desert. 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. See also: Andean orogeny and Arid DiagonalĪccording to the World Wide Fund for Nature, the Atacama Desert ecoregion occupies a continuous strip for nearly 1,600 km (1,000 mi) along the narrow coast of the northern third of Chile, from near Arica (18☂4′S) southward to near La Serena (29★5′S). The most arid region of the Atacama Desert is situated between two mountain chains, the Andes and the Chilean Coast Range, which are high enough to prevent moisture advection from either the Pacific or the Atlantic Ocean, creating a two-sided rain shadow effect. The constant temperature inversion caused by the cool north-flowing Humboldt Ocean current and the strong Pacific anticyclone contribute to the extreme aridity of the desert. The area has been used as an experimentation site for Mars expedition simulations due to its similarities to the Martian environment. It is the only hot true desert to receive less precipitation than polar deserts, and the largest fog desert in the world. The Atacama Desert is the driest nonpolar desert in the world, and the second driest overall, behind some specific spots within the McMurdo Dry Valleys. Stretching over a 1,600 km (990 mi) strip of land west of the Andes Mountains, it covers an area of 105,000 km 2 (41,000 sq mi), which increases to 128,000 km 2 (49,000 sq mi) if the barren lower slopes of the Andes are included. The Atacama Desert ( Spanish: Desierto de Atacama) is a desert plateau located on the Pacific coast of South America ( Argentina and Chile).
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