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Salar de Uyuni

Salar de Uyuni (or Salar de Tunupa) is the world's largest salt flat at . It is located in the Potosi and Oruro departments in southwest Bolivia, near the crest of the Andes, and is elevated 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, but that lithium is not being extracted yet. 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.

Formation, geology and climate

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 30,00042,000 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 , and an estimated age of 13,00018,000 or 14,90026,100 years depending on the source. The youngest prehistoric lake was Coipasa, which was radiocarbon dated to 11,50013,400 years. When it dried, it left behind two modern lakes, Poopo Lake and Uru Uru Lake, and two major salt deserts, Salar de Coipasa and the larger Salar de Uyuni. Salar de Uyini spreads over , 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 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 in November-January and a low of in June. The nights are however cold all through the year with temperatures between . The relative humidity is rather low and constant throughout the year at 3045 %. The rainfall is also low at per month between April and November, but it may increase up to in January. However, except for January, even in the rainy season the number of rainy days is below 5 per month.

Economic influence

The Salar contains large amounts of sodium, potassium, lithium and magnesium , as well as borax. Of those, lithium is arguably most important as it is a vital component of many electric batteries. With estimated , Bolivia holds about half of the world's lithium reserves; most of those are located in the Salar de Uyuni. Lithium is concentrated in the brine under the salt crust at a relatively high concentration of about 0.3%. It is also present in the top layers of the porous halite body lying under the brine; however the liquid brine is much easier to extract, simply by boring holes in the crust and pumping out the brine. The brine distribution has been monitored by the Landsat satellite and then confirmed in the ground drilling tests. Following those findings, an American-based international corporation has invested $137 million in the Bolivian economy to develop lithium extraction industry. However, lithium extraction in the 1980s and 1990s by foreign companies met strong opposition of the local community. Despite being poor, locals believed that the money raised by the mining would not reach them. There is currently no mining plant at the site and the Bolivian government doesn't want to allow exploitation by foreign corporations. Instead it intends to build its own pilot plant with a modest annual production of of lithium and to increase it to tonnes by 2012.

Salar de Uyuni is estimated to contain 10 billion tonnes tonnes of salt, of which less than is extracted annually. All miners working in the Salar belong to Colchani's cooperative.

Because of its location, large area and flatness, the Salar is a major car transport route across the Bolivian Altiplano.


Salar is salt flat in Spanish and Uyuni originates from the Aymara language and means a pen (enclosure). Thus Salar de Uyuni can be loosely translated as a salt flat with enclosures, the latter possibly referring to the "islands" of the Salar. Uyuni is also the name for a town of 10,600 people, which serves as a gateway for tourists visiting the Salar.

Aymara legend tells that the mountains Tunupa, Kusku and Kusina, which surround the Salar, were giant people. Tunupa married Kusku, but Kusku ran away from her with Kusina. Grieving Tunupa started to cry while breast-feeding her son. Her tears mixed with milk and formed the Salar. Many locals consider the Tunupa an important deity and say that the place should be called Salar de Tunupa rather than Salar de Uyuni.

Flora and fauna

File:FishIslandSalarUyuni.jpg|A part of the Incahuasi island inside the Salar featuring giant cacti

File:James Flamingo.jpg|James flamingo

File:Culpeo MC.jpg|Culpeo

File:Bolivian vizcacha.jpg|Bolivian vizcacha

File:Chloephaga melanoptera1.jpg|Andean goose

File:Andean Hillstar (Oreotrochilus estella) perched.jpg|Andean Hillstar

File:Andean Flamingos Laguna Colorada Bolivia Luca Galuzzi 2006.jpg|Andean flamingos in the Salar

The Salar is virtually devoid of any wild life and vegetation. The latter is dominated by giant cacti . They grow at a rate of about per year to a length of about . Other shrubs include Pilaya, which is used by locals to cure catarrh, and Thola (Baccharis dracunculifolia), which is burned as a fuel. Also present are quinoa plants and quenua bushes.

Every November, Salar de Uyuni is the breeding grounds for three species of pink South American flamingos: the Chilean, Andean and rare James's Flamingos, their color presumably originating from feeding on pink algae. There are about 80 of other bird species present, including the horned coot, the Andean goose and the Andean Hillstar. Andean fox (culpeo) is a representative animal, and the "islands" of Salar host a colony of rabbit-like viscachas.



Salar de Uyuni steadily attracts tourists from all around the world. As it is located far from the cities, a number of hotels have been raised in the area over the years. For several reasons, including lack of conventional construction materials, many of them are almost entirely built using salt blocks cut from the surface of the Salar. The first such hotel was erected in 1993-1995 in the middle of the salt flat, and soon became a popular tourist destination. However, its location in the center of a desert produced sanitary problems, as most waste had to be collected manually. Mismanagement caused serious environmental pollution and the hotel had to be dismantled in 2002. New salt hotels were built near the edges of the Salar, closer to the roads, and in full compliance with the environmental rules.

Train cemetery

One of the major tourist attractions of the area is an antique train cemetery. It is located outside Uyuni and is connected to it by the old train tracks. The town served in the past as a distribution hub for the trains carrying mineral on their way to the Pacific Ocean ports. The train lines were built by British engineers who arrived near the end of the 19th century and formed a sizeable community in Uyuni. The engineers were invited by British-sponsored Antofagasta and Bolivia Railway Companies, which is now Ferrocarril de Antofagasta a Bolivia. The rail construction started in 1888 and ended in 1892. It was encouraged by the then Bolivian President Aniceto Arce, who believed Bolivia would flourish with a good transport system, but it was also constantly sabotaged by the local Aymara indigenous Indians who saw it as an intrusion into their lives. The trains were mostly used by the mining companies. In the 1940s, the mining industry collapsed, partly because of the mineral depletion. Many trains were abandoned thereby producing the train cemetery. There are talks to build a museum out of the cemetery.

Satellite calibration

Some Earth observing satellites need to be precisely calibrated in terms the distance measurement while in orbit. For example, the primary objective of the NASAs Geoscience Laser Altimeter System (GLAS), which is installed on the Ice, Cloud and land Elevation Satellite (ICESat), is to detect changes in ice sheet elevations of as little as per year, over area. A common approach for calibrating the satellite elevation measurements is to compare them to an accurately surveyed terrestrial reference target. Salt flats are ideal for this purpose because they are large, stable surfaces having strong reflection, which is also similar to that of ice sheets. Salar de Uyuni is especially suitable because it is the largest salt flat in the world. In the low-rain period of from April to November, the skies above it are very clear, and the air is dry . Absence of large-scale industries in the area and the high ground elevation also contribute to the cleanness of the air. The Salar also has a stable surface which is smoothened by seasonal flooding (water dissolves the salt surface and thus keeps it leveled). As a result, the variation in the surface elevation over the area of Salar de Uyuni is less than , and there are square kilometers there which are flat within a few centimeters. The surface reflectivity (albedo) for ultraviolet light is relatively high at 0.69 and shows variations of only few percent during the daytime. Combination of all these features make Salar de Uyuni about five times better for satellite calibration than the surface of an ocean. Using Salar de Uyuni as the target, ICESat has already achieved the short-term elevation measurement accuracy of below .

That the surface of Salar de Uyuni is not perfectly flat is a recent finding due to the high precision of the modern GPS technology. New measurements revealed previously missed features resembling ridges, hills and valleys, on the height scale millimeters. They originate from the variation in material density, and thus in the gravitational force, underneath the Salar's sediments. Just as the ocean surface rises over denser seamounts, the salt flat surface also rises and falls to reflect the subsurface density variations.

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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article Salar de Uyuni

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