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'{{Use dmy dates|date=June 2021}} {{Short description|Salt flat in Bolivia}} {{Infobox landform | water = | name = Salar de Uyuni | photo = Salar Uyuni au01.jpg | photo_caption = Hexagonal formations on the surface of the Salar de Uyuni as a result of salt crystallization from evaporating water | elevation_m = 3663 | elevation_ref = | area = {{Convert|10582|km2|ha}} | depth = {{Convert|130|m|ft}} | formed_by = Evaporation | map = Bolivia | map_relief = 1 | map_caption = Location within Bolivia | label_position = none | ___location = [[Daniel Campos Province]], [[Potosí Department]] | coordinates = {{coord|20|08|01.59|S|67|29|20.88|W|scale:30000|display=inline,title}} | topo = | type = [[Salt pan (geology)|Salt pan]], [[dry lake]] | age = | volcanic_arc/belt = | last_eruption = }} '''Salar de Uyuni''' (or "Salar de Tunupa")<ref>{{cite web|title=Salar de Tunupa|url=http://www.irisentoreopreis.nl/tunupa_map.shtml|website=Iris en Tore op reis|access-date=26 February 2016|date=29 July 2011|archive-date=19 January 2016|archive-url=https://web.archive.org/web/20160119054358/http://www.irisentoreopreis.nl/tunupa_map.shtml|url-status=dead}}</ref> is the world's largest [[Salt pan (geology)|salt flat]], or [[Dry lake|playa]], at over {{convert|10,000|km2|mi2}} in area.<ref name="NASA2019">{{cite web |title=Lithium Harvesting at Salar de Uyuni |url=https://earthobservatory.nasa.gov/images/144976/lithium-harvesting-at-salar-de-uyuni |website=Earth Observatory | publisher=[[NASA]] |language=en |date=April 12, 2013}}</ref> It is in the [[Daniel Campos Province]] in [[Potosí Department|Potosí]] in southwest [[Bolivia]], near the crest of the [[Andes]] at an elevation of {{convert|3,656|m|ft|abbr=on}} above sea level.<ref name=britannica>{{Cite encyclopedia |title=Uyuni Salt Flat |encyclopedia=[[Encyclopædia Britannica]] |url=http://www.britannica.com/eb/article-90745/88?query=Salar%20de%20Uyuni&ct= |access-date=1 December 2007}}{{dead link|date=May 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> The Salar was formed as a result of transformations between several prehistoric lakes that existed around forty thousand years ago but had all evaporated over time.{{r|NASA2019}} It is now covered by a few meters of salt crust, which has an extraordinary flatness with the average elevation 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]]. The large area, clear skies, and exceptional flatness of the surface make the Salar ideal for calibrating the [[altimeter]]s of Earth observation satellites.<ref name=nature2/><ref name=geo/><ref name=refl/><ref>{{cite news |bibcode=2002AGUFMOS52A0193B |title=GPS Survey of the salar de Uyuni, Bolivia, for Satellite Altimeter Calibration |last=Borsa |first=A. A |publisher=American Geophysical Union, Fall Meeting |year=2002 |display-authors=etal}}</ref><ref name=ieee>{{cite journal |last1=Lamparelli |first1=R. A. C. |title=Characterization of the Salar de Uyuni for in-orbit satellite calibration |journal=[[IEEE Geoscience and Remote Sensing Society|IEEE Trans. Geosci. Remote Sens.]] |volume=41 |issue=6 |pages=1461–1468 |year=2003 |doi=10.1109/TGRS.2003.810713 |display-authors=1 |last2=Ponzoni |first2=F. J. |last3=Zullo |first3=J. |last4=Queiroz Pellegrino |first4=G. |last5=Arnaud |first5=Y. |bibcode = 2003ITGRS..41.1461C |s2cid=18716304 |url=https://semanticscholar.org/paper/6b6a5037f838a2342d5681b642944fd68c775551}}</ref> Following rain, a thin layer of dead calm water transforms the flat into the world's largest mirror, {{convert|129|km|mile|abbr=on}} across.<ref>{{cite news |url=http://www.pbs.org/kingdoms-sky/episodes/andes/ |title=Kingdoms of the Sky: Salt Flat Landscape Creates the World's Largest Mirror |newspaper=[[PBS]] |date=25 July 2018 |quote=Sudden rains leave a layer of dead calm water just an inch deep, turning the salt flat into a natural wonder: the world's largest mirror, eighty miles across. At night, the landscape is transformed again into a 360-degree starscape. This dazzling show is only possible because the Salar de Uyuni is perfectly flat.}}</ref> The Salar serves as the major transport route across the Bolivian [[Altiplano]] and is a prime breeding ground for several species of [[flamingo]]s. Salar de Uyuni is also a climatological transitional zone since the towering tropical [[Cumulus congestus cloud|cumulus congestus]] and [[cumulonimbus incus]] clouds that form in the eastern part of the salt flat during the summer cannot permeate beyond its drier western edges, near the Chilean border and the [[Atacama Desert]].{{citation needed|date=June 2016}} The Salar has been used as a filming ___location for movies such as ''[[Star Wars: The Last Jedi]]'' (2017; as planet Crait),<ref>{{cite web |title=Crait: The Salar de Uyuni Star Wars Planet |url=https://www.salardeuyuni.com/salar-de-uyuni-star-wars/ |website=salardeuyuni |publisher=salardeuyuni.com |access-date=11 April 2020}}</ref><ref>{{cite web |last1=Butler |first1=Alex |title=Star Wars: The Last Jedi filming locations around the world |url=https://www.lonelyplanet.com/articles/star-wars-the-last-jedi-filming-locations |website=Lonely Planet |publisher=Lonely Planet |access-date=11 April 2020}}</ref> ''[[The Fall (2006 film)|The Fall]]'' (2006), ''[[Salt and Fire]]'' (2016), ''The Unseen'' (2017), and several others. ==Formation, geology, and climate== [[File:Uyuni landsat.JPG|thumb|''Salar de Uyuni'' as viewed from space, with [[Coipasa Lake|''Salar de Coipasa'']] in the top left corner]] 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.<ref name=nasa>{{cite web |url=http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17120 |archive-url=https://web.archive.org/web/20061001054555/http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17120 |url-status=dead |archive-date=1 October 2006 |title=Salar de Uyuni, Bolivia |publisher=[[NASA Earth Observatory]] |access-date=1 December 2007}}</ref> ===History=== [[File:Salar_de_Uyuni,_Bolivia,_2016-02-04,_DD_10-12_HDR.JPG|thumb|left|Mountains surrounding the Uyuni salt flat during sunrise, [[Daniel Campos Province]], [[Potosí Department]], southwestern [[Bolivia]], not far from the crest of the [[Andes]]]] The geological history of the Salar is associated with a sequential transformation between several vast lakes. Some 30,000 to 42,000 years ago, the area was part of a giant prehistoric lake, [[Lake Minchin]]. Its age was estimated by [[radiocarbon dating]] shells from outcropping [[sediment]]s and [[Carbonate platform|carbonate reefs]] and varies between reported studies. Lake Minchin (named after Juan B. Minchin of Oruro)<ref>{{cite journal|author=Bowman, Isaiah |jstor=201641 |title=Results of an Expedition to the Central Andes |journal=Bulletin of the American Geographical Society |volume=46 |issue=3 |pages=161–183 |year=1914 |doi=10.2307/201641}}</ref> later transformed into [[Lake Tauca|Paleo Lake Tauca]] having a maximal depth of {{convert|140|m|sp=us}}, and an estimated age of 13,000 to 18,000 or 14,900 to 26,100 years, depending on the source. The youngest prehistoric lake was Coipasa, which was radiocarbon dated to 11,500 to 13,400 years ago. When it dried, it left behind two modern lakes, [[Lake Poopó|Poopó]] and [[Lago Uru Uru|Uru Uru]], and two major salt deserts, [[Lago Coipasa|Salar de Coipasa]] and the larger Salar de Uyuni. Salar de Uyuni spreads over 10,582&nbsp;km², which is roughly 100 times the size of the [[Bonneville Salt Flats]] in the United States. Lake Poopó is a neighbor of the much larger [[Lake Titicaca]]. During the wet season, Titicaca overflows and discharges into Poopó, which in turn, floods Salar De Coipasa and Salar de Uyuni.<ref name=nature>{{cite journal |journal=[[Nature (journal)|Nature]] |title=Tropical climate changes at millennial and orbital timescales on the Bolivian Altiplano |first1=P. A. |last1=Baker |volume=409 |year=2001 |pmid=11217855 |display-authors=1 |last2=Rigsby |first2=C. A. |last3=Seltzer |first3=G. O. |last4=Fritz |first4=S. C. |last5=Lowenstein |first5=T. K. |last6=Bacher |first6=N. P. |last7=Veliz |first7=C. |issue=6821 |pages=698–701 |doi=10.1038/35055524 |bibcode=2001Natur.409..698B |s2cid=4394703 |url=http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1046&context=geosciencefacpub}}</ref> Lacustrine mud that is interbedded with salt and saturated with brine underlies the surface of Salar de Uyuni. The brine is a saturated solution of [[sodium chloride]], [[lithium chloride]], and [[magnesium chloride]] in water. It is covered with a solid salt crust varying in thickness between tens of centimeters and a few meters. The center of the Salar contains a few islands, which are the remains of the tops of ancient volcanoes submerged during the era of Lake Minchin. They include unusual and fragile coral-like structures and deposits that often consist of fossils and algae.<ref name=trav1/> ===Climate=== The area has a relatively stable average temperature with a peak at {{cvt|21|°C}} in November to January, and a low of {{cvt|13|°C}} in June. The nights are cold all through the year, with temperatures between {{convert|-9|and|5|°C|°F|abbr=on}}. The relative humidity is rather low and constant throughout the year at 30% to 45%. The rainfall is also low at {{convert|1|to|3|mm|in|abbr=on}} per month between April and November, but it may increase up to {{convert|80|mm|in|abbr=on}} in January. However, except for January, even in the rainy season the number of rainy days is fewer than 5 per month.<ref name=ieee/> {{Wide image|Salar de Uyuni Décembre 2007 - Panorama 1 edit.jpg|1100px|[[Isla Incahuasi|Incahuasi island]] in the center of the Salar.}} ==Economic influence== [[File:Salt production Uyuni.JPG|thumb|Salt production at the Salar|alt=]] Located in the [[Lithium Triangle]], the Salar contains a large amount of [[sodium]], [[potassium]], [[lithium]] and [[magnesium]] (all in the chloride forms of [[Sodium chloride|NaCl]], [[Potassium chloride|KCl]], [[Lithium chloride|LiCl]] and [[Magnesium chloride|MgCl₂]], respectively), as well as [[borax]].<ref name=trav1/> With an estimated 9,000,000&nbsp;[[tonne|t]], Bolivia holds about 7% of the world's known lithium resources; most of those are in the Salar de Uyuni.<ref>{{cite news |url=http://minerals.usgs.gov/minerals/pubs/commodity/lithium/mcs-2011-lithi.pdf |title=Lithium Statistics and Information|publisher=USGS}}</ref> 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 easier to extract, by boring into the crust and pumping out the brine.{{citation needed|date=June 2020}} The brine distribution has been monitored by the [[Landsat program|Landsat]] satellite and confirmed in ground drilling tests. Following those findings, an American-based international corporation has invested $137&nbsp;million to developing lithium extraction.<ref>{{cite book |url=https://books.google.com/books?id=j0QrAAAAYAAJ&pg=PA60 |page=60 |title=Science and technology for development: prospects entering the twenty-first century : a symposium in commemoration of the twenty-fifth anniversary of the U.S. Agency for International Development |publisher=National Academies |year=1988 |author=National Research Council (U.S.). Board on Science and Technology for International Development, National Research Council (U.S.). Office of International Affairs|isbn=9780309320023 }}</ref> However, lithium extraction in the 1980s and 1990s by foreign companies met strong opposition from the local community. Locals believed that the money infused by mining would not reach them.<ref name="BBC_electric_car">{{cite news |title=Bolivia holds key to electric car future |url=http://news.bbc.co.uk/1/hi/business/7707847.stm |website=[[BBC News|BBC]]|date=9 November 2008 }}</ref> The lithium in the salt flats contains more impurities, and the wet climate and high altitude make it harder to process.<ref>{{cite web |last1=Eisler |first1=Matthew |title=Bolivian lithium: why you should not expect any 'white gold rush' in the wake of Morales overthrow |url=https://theconversation.com/bolivian-lithium-why-you-should-not-expect-any-white-gold-rush-in-the-wake-of-morales-overthrow-127139 |website=[[The Conversation (website)|The Conversation]] |language=en}}</ref> No mining plant is currently at the site, and the Bolivian government does not want to allow exploitation by foreign corporations. Instead, it intends to reach an annual production of 35,000&nbsp;t by 2023 in a joint venture with ACI Systems Alemania GmbH.<ref>{{Cite news |date=3 December 2018 |title=Bolivia's Almost Impossible Lithium Dream |url=https://www.bloomberg.com/news/features/2018-12-03/bolivia-s-almost-impossible-lithium-dream |access-date=26 March 2019 |newspaper=[[Bloomberg News|Bloomberg]]}}</ref><ref name="BBC_electric_car"/><ref name="ACISA">{{cite web |title=Lithium – ACI Systems Alemania GmbH |date=August 2019 |url=https://www.acisa.de/lithium/ |access-date=11 January 2020}}</ref> Salar de Uyuni is estimated to contain 10&nbsp;billion tonnes (9.8&nbsp;billion long tons; 11&nbsp;billion short tons) of salt, of which less than 25,000&nbsp;t 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]],<ref name=nasa/> except when seasonally covered with water.{{citation needed|date=June 2016}} ==Name== ''Salar'' means [[Salt pan (geology)|salt flat]] in Spanish. ''Uyuni'' originates from the [[Aymara language]] and means a [[pen (enclosure)]]; Uyuni is a surname and the name of a town that serves as a gateway for tourists visiting the Salar. Thus ''Salar de Uyuni'' can be loosely translated as a salt flat with enclosures, the latter possibly referring to the "islands" of the Salar; or as "salt-flat at Uyuni (the town named 'pen for animals')".{{citation needed|date=June 2016}} 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 breastfeeding 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.<ref name=trav1>{{cite book |url=https://books.google.com/books?id=WDBYHYwdhuAC&pg=PA174 |pages=170; 174–176 |title=Bolivia: The Bradt Travel Guide |first=David |last=Atkinson |publisher=Bradt Travel Guides |isbn=978-1-84162-165-4 |date=1 March 2007}}</ref> ==Flora and fauna== <gallery mode="packed"> File:FishIslandSalarUyuni.jpg|A part of [[Isla Incahuasi|Incahuasi Island]] inside the Salar, featuring giant [[cactus|cacti]] File:James Flamingo.jpg|[[James's 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 flamingo]]s in the [[Laguna Colorada]], south of the Salar File:VicunaSalarDeUyuni 20170503.jpg|[[Vicuñas]] near the Salar De Uyuni 2017 </gallery> The Salar is virtually devoid of any wildlife or vegetation. The latter is dominated by giant cacti (''[[Echinopsis]] atacamensis pasacana'', ''Echinopsis tarijensis'', etc.). They grow at a rate of about 1&nbsp;cm/a to a height of about {{convert|12|m|ft|abbr=on}}. 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 [[Polylepis rugulosa|queñua]] bushes.<ref name=trav1/> Every November, Salar de Uyuni is the breeding ground for three South American species of [[flamingo]] feeding on local [[brine shrimp]]s: the [[Chilean flamingo|Chilean]], [[Andean flamingo|Andean]], and rare [[James's flamingo]]s. About 80 other bird species are present, including the [[horned coot]], [[Andean goose]], and [[Andean hillstar]]. The Andean fox, or [[culpeo]], is also present, and islands in the Salar (in particular [[Isla Incahuasi|Incahuasi Island]]) host colonies of rabbit-like [[viscacha]]s.<ref name=trav1/> ==Tourism== ===Hotels=== {{See also|Palacio de Sal}} [[File:SalarDeUyuniSaltProduction.jpg|thumb|Traditional salt production at Salar. Such salt blocks are used for building [[Palacio de Sal|salt hotel]]s]] Salar de Uyuni is a popular tourist destination, and consequently a number of hotels have been built in the area. Due to lack of conventional construction materials, many of them are almost entirely (walls, roof, furniture) built with salt blocks cut from the Salar. The first such hotel, named [[Palacio de Sal]], was erected in 1993–1995<ref name=lick2>{{cite web|url=http://www.hotelchatter.com/story/2009/1/26/231522/848/hotels/Bolivian_Hotel_Truly_Is_the_Salt_of_the_Earth|work=hotelchatter.com|title=Bolivian Hotel Truly Is the Salt of the Earth|date=27 January 2009|access-date=16 October 2009|archive-date=15 May 2013|archive-url=https://web.archive.org/web/20130515053921/http://www.hotelchatter.com/story/2009/1/26/231522/848/hotels/Bolivian_Hotel_Truly_Is_the_Salt_of_the_Earth|url-status=dead}}</ref><ref name=lick1>{{cite web |url=http://www.tripcrazed.com/702316570/dont-lick-the-walls-of-the-salt-hotel/ |title=Don't Lick the Walls of the Salt Hotel |website=Tripcrazed.com |date=19 May 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090523140538/http://www.tripcrazed.com/702316570/dont-lick-the-walls-of-the-salt-hotel/ |archive-date=23 May 2009}}</ref> in the middle of the salt flat,<ref name=lick3>{{cite web |first=Peter |last=McFarrren |publisher=The [[Associated Press]] |url=http://www.seattlepi.com/getaways/030499/salt04.html |title=Salt hotel has a rule: No licking |date=4 March 1999 }}{{Dead link|date=April 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref name=book1>{{cite book |url=https://archive.org/details/peruboliviaecuad00benb |url-access=registration |page=[https://archive.org/details/peruboliviaecuad00benb/page/378 378] |title=Peru, Bolivia & Ecuador |first1=Ben |last1=Box |author2=Kunstaetter, Robert |author3=Kunstaetter, Daisy |author4=Groesbeck, Geoffrey |publisher=Footprint Travel Guides |year=2007 |isbn=978-1-906098-06-3}}</ref> and soon became a popular tourist destination.<ref name=ng>{{cite web |url=http://news.nationalgeographic.com/news/2007/07/070725-salt-hotel.html |title=Photo in the News: New Salt Hotel Built in Bolivia |publisher=The [[National Geographic]] |date=25 July 2007 |access-date=1 September 2009}}</ref> However, its ___location in the center of a desert caused sanitation problems, as most waste had to be collected manually. Mismanagement caused serious environmental pollution and the hotel had to be dismantled in 2002.<ref>{{cite book |url=https://books.google.com/books?id=peBeMlMgcD4C&pg=PA259 |page=259 |title=The Rough Guide to South America |first=Harry |last=Adès |publisher=[[Rough Guides]] |year=2004 |isbn=1-85828-907-6}}</ref><ref name=german>{{cite web |language=de |work=hbernreuther.de |url=http://www.hbernreuther.de/Brasilien_Bolivien/Palacio_del_Sal/palacio_del_sal.html |title=Palacio del Sal |url-status=dead |archive-url=https://web.archive.org/web/20081206050825/http://www.hbernreuther.de/Brasilien_Bolivien/Palacio_del_Sal/palacio_del_sal.html |archive-date=6 December 2008}}</ref> Around 2007, a new hotel was built,<ref name=ng/> under the name Palacio de Sal, in a new ___location at the eastern edge of Salar de Uyuni, 25&nbsp;km away from the town of [[Uyuni]].<ref name=book1/> The sanitary system has been restructured to comply with the government regulations.<ref name=lick2/> The hotel has a dry sauna and a steam room, a saltwater pool and whirlpool baths.<ref>{{cite web|url=http://www.palaciodesal.com/|title=Homepage of Palacio de Sal|language=Spanish|access-date=2009-09-04|archive-url=https://web.archive.org/web/20120226233554/http://www.palaciodesal.com/|archive-date=2012-02-26|url-status=dead}}</ref> ===Train cemetery=== One major tourist attraction is an antique train cemetery. It is {{convert|3|km|mile|abbr=on}} 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 minerals en route to Pacific Ocean ports. The rail lines were built by British engineers arriving near the end of the 19th century and formed a sizeable community in Uyuni. The engineers were invited by the British-sponsored Antofagasta and Bolivia Railway Companies, now [[Ferrocarril de Antofagasta a Bolivia]]. The rail construction started in 1888 and ended in 1892. It was encouraged by 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 mineral depletion. Many trains were abandoned, producing the train cemetery. There are proposals to build a museum from the cemetery.<ref name=trav1/> {{Wide image|Uyuni Décembre 2007 - Cimetière de Trains 1.jpg|1100px|Cemetery of trains near the town of [[Uyuni]]}} ===Accidents=== Fatal accidents have occurred at the salt flat as a result of poorly maintained vehicles, untrained drivers, speeding, a disregard for the inhospitable conditions, and lack of regulation for tour companies.<ref>{{cite web | url=https://www.uyuniguide.com/accidents-in-uyuni/ | title=Updated List of Accidents on Salar de Uyuni Tours - }}</ref> ==Satellite calibration== Salt flats are ideal for calibrating the distance measurement equipment of satellites because they are large, stable surfaces with strong reflection, similar to that of ice sheets. As the largest salt flat on Earth, Salar de Uyuni is especially suitable for this purpose.<ref name="NASA2019" /> In the low-rain period from April to November, due to the absence of industry and its high elevation, the skies above Salar de Uyuni are very clear, and the air is dry (relative humidity is about 30%; rainfall is roughly {{convert|1|mm|disp=or}} per month). It has a stable surface, smoothed by seasonal flooding&nbsp;— water dissolves the salt surface and thus keeps it leveled.<ref>{{cite journal |last1=Borsa |first1=A. A. |last2=Bills |first2=B. G. |last3=Minster |first3=J. B. |year=2008 |title=Modeling the topography of the salar de Uyuni, Bolivia, as an equipotential surface of Earth's gravity field |journal=Journal of Geophysical Research: Solid Earth |volume=113 |issue=B10 |doi=10.1029/2007jb005445|bibcode=2008JGRB..11310408B |url=https://escholarship.org/content/qt0fr1z3fs/qt0fr1z3fs.pdf?t=lnr314 }}</ref> As a result, the variation in the surface elevation over the {{convert|10582|sqkm|sp=us|adj=on}} area of Salar de Uyuni is less than {{convert|1|m|sp=us}} normal to the Earth's circumference, and there are few square kilometers on Earth that are as flat. The surface reflectivity ([[albedo]]) for ultraviolet light is relatively high at 0.69 and shows variations of only a few percent during the daytime.<ref name=refl>{{cite journal |journal=Journal of Photochemistry and Photobiology B |volume=87 |issue=1 |year=2007 |pages=1–8 |title=Investigations on the effect of high surface albedo on erythemally effective UV irradiance: Results of a campaign at the Salar de Uyuni, Bolivia |doi=10.1016/j.jphotobiol.2006.12.002 |first1=Joachim |last1=Reuder |url=http://www.lfabolivia.org/wp-content/uploads/2008/12/final-uyuni.pdf |format=free-download pdf |pmid=17227712 |display-authors=1 |last2=Ghezzi |first2=F. |last3=Palenque |first3=E. |last4=Torrez |first4=R. |last5=Andrade |first5=M. |last6=Zaratti |first6=F. |url-status=dead |archive-url=https://web.archive.org/web/20140414175025/http://www.lfabolivia.org/wp-content/uploads/2008/12/final-uyuni.pdf |archive-date=14 April 2014}}</ref> The combination of all these features makes Salar de Uyuni about five times better for satellite calibration than the surface of an ocean.<ref name=nature2>{{Cite news |title=The salt flat with curious curves |first=Eric |last=Hand |date=30 November 2007 |publisher=[[Nature (journal)|Nature]] |url=http://www.nature.com/news/2007/071130/full/news.2007.315.html}}</ref><ref name=geo>{{cite journal |title=Assessment of ICESat performance at the salar de Uyuni, Bolivia |first=H. A. |last=Fricker |journal=[[Geophysical Research Letters]] |volume=32 |page=L21S06 |doi=10.1029/2005GL023423 |year=2005 |issue=21 |bibcode=2005GeoRL..3221S06F |doi-access=free}}</ref><ref name=gpsdaily>{{Cite news |title=The Hills And Valleys Of Earth's Largest Salt Flat |date=29 November 2007 |publisher=GPS Daily |url=http://www.gpsdaily.com/reports/The_Hills_And_Valleys_Of_Earth_Largest_Salt_Flat_999.html}}</ref> Using Salar de Uyuni as the target, ICESat has already achieved the short-term elevation measurement accuracy of below {{convert|2|cm|sp=us}}.<ref>{{cite book |url=https://books.google.com/books?id=CeLCxydgA8UC&pg=PA22 |page=22 |title=Satellite-based Estimates of Sea Ice Volume Flux: Applications to the Fram Strait Region |first=Gunnar |last=Spreen |publisher=GRIN Verlag |year=2008 |isbn=978-3-640-13064-1}}</ref> By using data from [[Multi-angle imaging spectroradiometer|MISR]] to perform passive optical [[bathymetry]] when the flat is flooded and calibrating the resultant water depth model with topographical data from the laser altimeter of [[ICESat]], it has been shown that the Salar de Uyuni is not perfectly flat. The 2006 analysis revealed previously missed features: ridges between 20 and 30 centimetres in height that are roughly sinusoidal with a wavelength of 5&nbsp;km (clearly visible in 1973 and 1975 [[LandSat]] images, and still in the same places decades later), and a moat around the periphery that is 1–3&nbsp;km wide and 20 to 50&nbsp;cm deep. They originate from the variation in material density, and thus the gravitational force, beneath 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.<ref name=gpsdaily/><ref>{{cite journal |journal=[[Remote Sensing of Environment]] |volume=107 |issue=1–2 |year=2007 |pages=240–255 |title=MISR-based passive optical bathymetry from orbit with few-cm level of accuracy on the Salar de Uyuni, Bolivia |first1=Bruce G. |last1=Bills |doi=10.1016/j.rse.2006.11.006 |display-authors=1 |last2=Borsa |first2=A. |last3=Comstock |first3=R. |bibcode=2007RSEnv.107..240B |url=https://zenodo.org/record/1259333}}</ref> {{Clear}} ==Gallery== {{Wide image|Salar de Uyuni Décembre 2007 - Centre de Nulle Part.jpg|2000px|Panoramic view of the Salar.}} <gallery mode="packed"> File:Salar de Uyuni 2013.jpg|Salar de Uyuni 2013 File:Piles of Salt Salar de Uyuni Bolivia Luca Galuzzi 2006 a.jpg|Piles of salt at the Salar File:Salar Uyuni au02.jpg|Llamas in the Salar File:Reflection on the Salar de Uyuni, bolivia.jpg|Reflection on the Salar de Uyuni File:Salar de Uyuni, Bolivia, 2016-02-04, DD 16-18 HDR.JPG|Reflections at sunset </gallery> == See also == * [[Ouki]] * [[Puka Mayu (Potosí)|Puka Mayu]] * [[Great Salt Lake]] * [[Rann of Kutch]] ==References== {{Reflist|30em}} ==External links== {{Commons category|Salar de Uyuni}} * {{Wikivoyage-inline|Salar de Uyuni}} *[https://www.salardeuyuni.com/ Salar de Uyuni official website] {{Altiplano lakes and paleolakes |state=expanded}} {{Authority control}} [[Category:Salt flats of Bolivia|Uyuni]] [[Category:Landforms of Oruro Department]] [[Category:Landforms of Potosí Department]] [[Category:Endorheic lakes of South America]] [[Category:Tourist attractions in Oruro Department]] [[Category:Tourist attractions in Potosí Department]] [[Category:Altiplano]]'