View source for Dry lake

{{Short description|Area that contained a standing surface water body}}
{{Other uses|Dry Lake (disambiguation)}}
[[File:Hows-e Sultan.jpg|thumb|[[Namak Lake]], [[Qom Province]], [[Iran]]]]
A '''dry lake bed''', also known as a '''playa''' ({{IPAc-en|'|p|l|aɪ|-|ə}}), is a basin or [[Depression (geology)|depression]] that formerly contained a standing surface water body, which disappears when evaporation processes exceed recharge. If the floor of a dry lake is covered by deposits of alkaline compounds, it is known as an '''alkali flat.''' If covered with salt, it is known as a ''[[salt pan (geology)|salt flat]].''
==Terminology==
If its basin is primarily [[salt]], then a dry lake bed is called a ''[[salt pan (geology)|salt pan]]'', ''pan'', or ''salt flat'' (the latter being a remnant of a [[salt lake]]). ''Hardpan'' is the dry terminus of an internally drained basin in a dry climate, a designation typically used in the [[Great Basin]] of the western United States.{{Citation needed|date=February 2018}}
[[File:Tunisia 10-12 - 141 - Salt Flats (6609472321).jpg|thumb|The [[Chott el Djerid]] in [[Tunisia]]]]
Another term for dry lake bed is ''playa''. The Spanish word ''playa'' ({{IPA|es|ˈplaʝa|pron}}) literally means "beach". Dry lakes are known by this name in some parts of Mexico and the western United States. This term is used e.g. on the [[Llano Estacado]] and other parts of the Southern [[High Plains (United States)|High Plains]] and is commonly used to address [[paleolake]] sediments in the [[Sahara]] like [[Lake Ptolemy]].
In South America, the usual term for a dry lake bed is ''salar'' or ''salina'', Spanish for ''salt pan''.
''Pan'' is the term used in most of South Africa. These may include the small round [[highveld]] pans, typical of the [[Chrissiesmeer]] area, to the extensive pans of the [[Northern Cape]] province.
Terms used in Australia include ''salt pans'' (where [[evaporite]] minerals are present) and ''clay pans''.<ref>[[Charles Rowland Twidale|Twidale, C.R.]] & Campbell, E.M. (2005, revised edition): ''Australian landforms: understanding a low, flat, arid and old landscape.'' Rosenberg Publishing. Pp. 227, 235, 237, 239. {{ISBN|1 877058 32 7}}</ref>
In Arabic, a salt flat is called a ''[[sabkha]]'' (also spelled ''sabkhah'', ''subkha'' or ''sebkha'') or ''shott'' (''[[chott]]''). In Central Asia, a similar "cracked mud" salt flat is known as a [[takir (soil)|takyr]]. In [[Iran]] salt flats are called ''kavir''.
==Formation==
[[File:Piles of Salt Salar de Uyuni Bolivia Luca Galuzzi 2006 a.jpg|thumb|{{center|Salt harvesting in [[Salar de Uyuni]], [[Bolivia]], the world's largest salt flat}}]]
[[File:Racetrack Playa in Death Valley National Park.jpg|thumb|upright|[[Sailing stone]] in [[Racetrack Playa]]]]
A dry lake is formed when water from rain or other sources, like intersection with a water table, flows into a dry depression in the landscape, creating a pond or lake. If the total annual evaporation rate exceeds the total annual inflow, the depression will eventually become dry again, forming a dry lake. Salts originally dissolved in the water precipitate out and are left behind, gradually building up over time. A dry lake appears as a flat bed of clay, generally encrusted with precipitated salts. These evaporite minerals are a concentration of weathering products such as sodium carbonate, borax, and other salts. In deserts, a dry lake may be found in an area ringed by [[Bajada (geography)|bajada]]s.
Dry lakes are typically formed in semi-[[arid]] to arid regions of the world. The largest concentration of dry lakes (nearly 22,000) is in the southern High Plains of [[Texas]] and eastern [[New Mexico]].{{citation needed|date=December 2009}} Most dry lakes are small. However, [[Salar de Uyuni]] in [[Bolivia]], near [[Potosí]], the largest salt flat in the world, comprises 4,085 square miles (10,582 square km).<ref>[http://www.britannica.com/EBchecked/topic/621014/Uyuni-Salt-Flat "Uyuni Salt Flat"] ''Encyclopædia Britannica</ref>
Many dry lakes contain shallow water during the rainy season, especially during wet years. If the layer of water is thin and is moved around the dry lake bed by wind, an exceedingly hard and smooth surface may develop. Thicker layers of water may result in a "cracked-mud" surface and [[teepee structure]] desiccation features. If there is very little water, [[dune]]s can form.
The [[Racetrack Playa]], located in [[Death Valley, California]], features a geological phenomenon known as "[[sailing stones]]" that leave linear "racetrack" imprints as they slowly move across the surface without human or animal intervention. These rocks have been recently filmed in motion by the [[Scripps Institution of Oceanography]] at the [[University of California, San Diego]] and are due to a perfect coincidence of events. First, the playa has to fill with water, which must be deep enough to form floating ice during winter, but still shallow enough that the rocks are exposed. When the temperature drops at night, this pond freezes into thin sheets of "windowpane" ice, which then must be thick enough to maintain strength, but thin enough to move freely. Finally, when the sun comes out, the ice melts and cracks into floating panels; these are blown across the playa by light winds, propelling the rocks in front of them.<ref>{{cite journal|title=Sliding Rocks on Racetrack Playa, Death Valley National Park: First Observation of Rocks in Motion |journal=PLOS ONE |date=2014-08-27 |doi=10.1371/journal.pone.0105948 |doi-access=free |last1=Norris |first1=Richard D. |last2=Norris |first2=James M. |last3=Lorenz |first3=Ralph D. |last4=Ray |first4=Jib |last5=Jackson |first5=Brian |volume=9 |issue=8 |pages=e105948 |pmid=25162535 |pmc=4146553 |bibcode=2014PLoSO...9j5948N }}</ref> The stones only move once every two or three years and most tracks last for three or four years.<ref>{{cite web|url=http://barnesos.net/publications/papers/2011.01.AJP.Lorenz.Racetrack.Rafts.pdf |title=Ice rafts not sails: Floating the rocks at Racetrack Playa |website=Barnesos.net |access-date=2016-06-24}}</ref>
==Ecology==
While a dry lake bed is itself typically devoid of vegetation, they are commonly ringed by [[shadscale]], [[saltbrush]] and other salt-tolerant plants that provide critical winter fodder for [[livestock]] and other [[herbivore]]s.
[[File:Seasonally flooded playa in SW Idaho.JPG|thumb|Playa in southwest Idaho, home to a number of rare species that occur nowhere else including ''[[Lepidium davisii]]'' (Davis' peppergrass) and ''[[Branchinecta raptor]]'' - a recently discovered giant [[fairy shrimp]].]]
In southwest [[Idaho]] and parts of [[Nevada]] and [[Utah]] there are a number of rare species that occur nowhere else but in the inhospitable environment of seasonally flooded playas. A new species of [[giant fairy shrimp]] was found in 2006. Although a large predatory species, it evaded detection because of the murkiness of the playa's water caused by winds and a fine clay load. This shrimp species is able to regenerate using tiny undetectable cysts that can remain in a dry lake bed for years until conditions are optimum for hatching.<ref>{{cite journal|last = Rogers|first = D. Christopher|year = 2006|title = A New Giant Species of Predatory Fairy Shrimp from Idaho, USA (Branchiopoda: Anostraca)|journal = Journal of Crustacean Biology|volume = 26|issue = 1|pages = 1–12|doi = 10.1651/C-2509.1|author2 = Quinney, Weaver, Olesen|doi-access = free}}</ref>
''[[Lepidium davisii]]'' is another rare species, a perennial plant whose habitat is restricted to playas in [[southern Idaho]] and northern Nevada.<ref name="hagwood1">{{cite web|last=Hagwood|first=Sheri|title=Sensitive Plants of the JRA|url=http://www.blm.gov/pgdata/etc/medialib/blm/id/publications/technical_bulletins.Par.98306.File.dat/tb06-01.pdf|publisher=Idaho BLM|access-date=2 May 2014|url-status=dead|archive-url=https://web.archive.org/web/20140503002232/http://www.blm.gov/pgdata/etc/medialib/blm/id/publications/technical_bulletins.Par.98306.File.dat/tb06-01.pdf|archive-date=3 May 2014}}</ref>
Far from major rivers or lakes, playas are often the only water available to wildlife in the desert. [[Antelope]] and other wildlife gather there after rainstorms to drink.
Threats to dry lakes include pollution from concentrated animal feeding operations such as cattle [[feedlot]]s and dairies. Results are erosion; fertilizer, pesticide and sediment runoff from farms; and [[overgrazing]].<ref name="hagwood1"/> A non-native shrub that has been used for rangeland restoration in the west, ''[[Kochia prostrata]]'', also poses a significant threat to playas and their associated rare species, as it capable of crowding out native vegetation and draining a playa's standing water because of its root growth.
==Human use==
[[File:01-2007-Trona-CA-01.jpg|thumb|[[The Mosaic Company]] chemical plant processes brines from [[Searles Dry Lake]] to make such products as [[trona]]]]
The extremely flat, smooth, and hard surfaces of dry lake beds make them ideal for fast motor vehicles and motorcycles. Large-sized dry lakes are excellent spots for pursuing [[land speed record]]s, as the smoothness of the surface allows low-clearance vehicles to travel very fast without any risk of disruption by surface irregularities, and the path traveled has no obstacles to avoid. The dry lake beds at [[Bonneville Salt Flats]] in Utah and [[Black Rock Desert]] in [[Nevada]] have both been used for setting land speed records. [[Lake Eyre]] and [[Lake Gairdner]] in [[South Australia]] have also been used for various land speed record attempts. Dry lake beds that rarely fill with water are sometimes used as locations for air bases for similar reasons. Examples include [[Groom Lake (salt flat)|Groom Lake]] at [[Area 51]] in Nevada and [[Edwards Air Force Base]] (known initially as Muroc Dry Lake) in California.
[[Brine]]s from the subsurface of dry lakes are often [[solution mining|exploited]] for valuable minerals in solution. See, for example, [[Searles Dry Lake]] and [[Lithium#Production and world supply|Lithium resources]].
Under United States law, a "playa lake" may be considered isolated [[wetland]]s and may be eligible to enroll in the new wetlands component of the [[Conservation Reserve Program]], enacted in the [[2002 farm bill]] (P.L. 107–171, Sec. 2101).<ref>{{cite web|url=http://ncseonline.org/nle/crsreports/05jun/97-905.pdf |title=CRS Report for Congress: Agriculture: A Glossary of Terms, Programs, and Laws, 2005 Edition - Order Code 97-905 |access-date=November 30, 2009 |quote=A temporary lake created in the lowest elevation of a basin in an arid area that has no surface drain into another water body, such as a perennial stream or river. Lake water is removed either by evaporation into the air or seepage into the ground. |url-status=dead |archive-url=https://web.archive.org/web/20110810044532/http://ncseonline.org/nle/crsreports/05jun/97-905.pdf |archive-date=August 10, 2011 }}</ref>
The [[Burning Man]] yearly event takes place in a playa in the [[Black Rock Desert]] in western Nevada every year.
Fangfang Yao et al (2023),<ref>{{Cite journal |last1=Yao |first1=Fangfang |last2=Livneh |first2=Ben |last3=Rajagopalan |first3=Balaji |last4=Wang |first4=Jida |last5=Crétaux |first5=Jean-François |last6=Wada |first6=Yoshihide |last7=Berge-Nguyen |first7=Muriel |date=2023-05-19 |title=Satellites reveal widespread decline in global lake water storage |url=https://www.science.org/doi/10.1126/science.abo2812 |journal=Science |language=en |volume=380 |issue=6646 |pages=743–749 |doi=10.1126/science.abo2812 |pmid=37200445 |bibcode=2023Sci...380..743Y |s2cid=258765167 |issn=0036-8075|hdl=10754/691878 |hdl-access=free }}</ref> at the University of Virginia reported that more than half of the world's large lakes are drying up. They assessed almost 2,000 large lakes using satellite measurements combined with climate and hydrological models. They found that unsustainable human use, changes in rainfall and run-off, sedimentation, and rising temperatures have driven lake levels down globally, with 53% of lakes showing a decline from 1992 to 2020.<ref>{{Cite news |last=Dickie |first=Gloria |author-link=Gloria Dickie |date=2023-05-19 |title=More than half of the world's large lakes are drying up, study finds |language=en |work=Reuters |url=https://www.reuters.com/business/environment/more-than-half-worlds-large-lakes-are-drying-up-study-finds-2023-05-18/ |access-date=2023-05-20}}</ref>
==Gallery==
<gallery class="center" widths="180px" heights="180px">
File:Devil's Golf Course in Death Valley NP.jpg|Devil's Golf Course in [[Death Valley National Park]], western United States
Image:Lake Hart.jpg|{{center|The dry lake and shore of [[Lake Hart, Australia|Lake Hart]], an [[endorheic]] desert lake in [[South Australia]].}}
Image:Jfader playa.jpg|{{center|A closeup photograph of salt growths on the crust of a dry lake.}}
Image:EtoshaPan 2005-06 comparison.jpg|{{center|[[Etosha pan]] in northern [[Namibia]]}}
</gallery>
==See also==
{{Portal|Lakes}}
* {{annotated link|List of drying lakes}}
* [[Lake]]
* {{annotated link|Cienega}}
* {{annotated link|Salt storm}}
* {{annotated link|Soil salinity}}
==References==
{{Reflist}}
==Bibliography==
* {{cite journal
| last = Briere
| first = Peter R.
|date=May 2002
| title = Playa, playa lake, sabkha: Proposed definitions for old terms
| journal = Journal of Arid Environments
| volume = 45
| issue = 1
| pages = 1–7
| publisher = Elsevier
| doi = 10.1006/jare.2000.0633
}}<!--| access-date = 2008-05-20-->
*John H. Wellington, ''Southern Africa: a geographical study'', Chapter 16 LAKES AND PANS
{{Commons category|Dry lakes}}
{{Earth's landforms}}
{{Authority control}}
[[Category:Salt flats| ]]
[[Category:Endorheic lakes]]
[[Category:Aeolian landforms]]
[[Category:Lacustrine landforms]]