Salar de Uyuni (or Salar de Tunupa) is the world’s largest salt flat at 10,582 square kilometers (4,086 sq mi). It is located in the Potosí and Oruro departments in southwest Bolivia, near the crest of the Andes, and is elevated 3,656 meters (11,995 ft) above the mean sea level. The Salar was formed as a result of transformations between several prehistoric lakes. It is covered by a few meters of salt crust, which has an extraordinary flatness with the average altitude variations within one meter over the entire area of the Salar.
The crust serves as a source of salt and covers a pool of brine, which is exceptionally rich in lithium. It contains 50 to 70% of the world’s lithium reserves, which has yet to be extracted. The large area, clear skies and exceptional surface flatness make the Salar an ideal object for calibrating the altimeters of the Earth observation satellites.The Salar serves as the major transport route across the Bolivian Altiplano and is a major breeding ground for several species of pink flamingos.
Salar de Uyuni is part of the Altiplano of Bolivia in South America. The Altiplano is a high plateau, which was formed during uplift of the Andes mountains. The plateau includes fresh and saltwater lakes as well as salt flats and is surrounded by mountains with no drainage outlets.
The geological history of the Salar is associated with a sequential transformation between several vast lakes. Some 30,000–42,000 years ago, the area was part of a giant prehistoric lake, Lake Minchin. Its age was estimated from radiocarbon dating of shells from outcropping sediments and carbonate reefs and varies between reported studies. Lake Minchin (named after the Juan B. Minchin of Oruro) later transformed into paleolake Tauca having a maximal depth of 140 meters (460 ft), and an estimated age of 13,000–18,000 or 14,900–26,100 years depending on the source.
The youngest prehistoric lake was Coipasa, which was radiocarbon dated to 11,500–13,400 years. When it dried, it left behind two modern lakes, Poopó Lake and Uru Uru Lake, and two major salt deserts, Salar de Coipasa and the larger Salar de Uyuni. Salar de Uyini spreads over 10,582 square kilometers (4,086 sq mi), which is roughly 25 times the size of the Bonneville Salt Flats in the United States. Lake Poopo is a neighbor of the much larger lake Titicaca. During the wet season, Titicaca overflows and discharges into Poopo, which, in turn, floods Salar De Coipasa and Salar de Uyuni.
Underneath the surface of the Salar is a lake of brine 2 to 20 meters (7 to 66 ft) deep. The brine is a saturated solution of table salt, lithium chloride and magnesium chloride in water. It is covered with a solid salt crust with a thickness varying between tens of centimeters to a few meters. The center of the Salar contains a few “islands”, which are the remains of the tops of ancient volcanoes which were submerged during the era of lake Minchin. They include unusual and fragile coral-like structures and deposits that often consist of fossils and algae.
The area has a relatively stable average temperature with a peak at 21 °C (70 °F) in November-January and a low of 13 °C (55 °F) in June. The nights are however cold all through the year with temperatures between -9 and 5 °C (16 and 41 °F). The relative humidity is rather low and constant throughout the year at 30–45 %. The rainfall is also low at 1–3 millimeters (0.039–0.12 in) per month between April and November, but it may increase up to 70 millimeters (2.8 in) in January. However, except for January, even in the rainy season the number of rainy days is below 5 per month.
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