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A dry lake bed, also known as a playa, is a basin or depression that formerly contained a standing surface water body, which disappeared when evaporation processes exceeded 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 flat.''


Terminology

If its basin is primarily
salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crystallinity, crystalline mineral is known as rock salt or halite. Sa ...

salt
, then a dry lake bed is called a '' salt pan'', ''pan'', or ''salt flat'' (the latter being a remnant of a
salt lake A salt lake or saline lake is a landlocked body of water (Lysefjord) in Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokmål (, ; literally "book tongue") is an official wr ...

salt lake
). ''Hardpan'' is the dry terminus of an internally drained basin in a dry climate, a designation typically used in the
Great Basin The Great Basin is the largest area of contiguous endorheic watersheds in North America North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can also be described as the ...
of the western United States. Another term for dry lake bed is ''playa''. The Spanish word ''playa'' () literally means "beach". Dry lakes are known by this name in some parts of Mexico and the western United States. This term is also used on the
Llano Estacado The Llano Estacado (), commonly known as the Staked Plains, is a region in the Southwestern United States that encompasses parts of eastern New Mexico and northwestern Texas. One of the largest mesas or tablelands on the North American continent, t ...
and other parts of the Southern High Plains. 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 The Highveld (Afrikaans File:WIKITONGUES- Alaric speaking Afrikaans.webm, Alaric speaking Afrikaans. Afrikaans (, ) is a West Germanic languages, West Germanic language spoken in South Africa, Namibia and, to a lesser extent, Botswana, Zambia ...
pans, typical of the
Chrissiesmeer Chrissiesmeer (Lake Chrissie) is a small town situated in Msukaligwa Local Municipality, in a wetland area of Mpumalanga province in South Africa, on the northern banks of the eponymous Lake Chrissie. The Bushmen, San inhabited this area along w ...
area, to the extensive pans of the
Northern Cape The Northern Cape ( af, Noord-Kaap; xh, eMntla-Koloni; tn, Kapa Bokone) is the largest and most sparsely populated Provinces of South Africa, province of South Africa. It was created in 1994 when the Cape Province was split up. Its capital is Ki ...
province. Terms used in Australia include ''salt pans'' (where
evaporite An evaporite () is a water-soluble Solubility is the property of a solid, liquid or gaseous chemical substance called ''solution, solute'' to dissolve in a solid, liquid or gaseous solvent. The solubility of a substance fundamentally depend ...
minerals are present) and ''clay pans''. In Arabic, a salt flat is called a ''
sabkha A term typically used by Earth scientists, a sabkha ( ar, سبخة) is a coastal, supratidal mudflat or sandflat in which evaporite An evaporite () is a water-soluble Solubility is the property of a solid, liquid or gaseous chemical s ...
'' (also spelled ''sabkhah'', ''subkha'' or ''sebkha'') or ''shott'' (''
chott In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the processes ...
''). In Central Asia, a similar "cracked mud" salt flat is known as a takyr. In
Iran Iran ( fa, ایران ), also called Persia, and officially the Islamic Republic of Iran, is a country in Western Asia Western Asia, West Asia, or Southwest Asia, is the westernmost subregion A subregion is a part of a larger regio ...

Iran
salt flats are called ''kavir''.


Formation

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 bajadas. Dry lakes are typically formed in semi-
arid A region is arid when it is characterized by a severe lack of available water, to the extent of hindering or preventing the growth and development Development or developing may refer to: Arts *Development hell, when a project is stuck in d ...

arid
to arid regions of the world. The largest concentration of dry lakes (nearly 22,000) is in the southern High Plains of
Texas Texas (, ; Spanish Spanish may refer to: * Items from or related to Spain: **Spaniards, a nation and ethnic group indigenous to Spain **Spanish language **Spanish cuisine Other places * Spanish, Ontario, Canada * Spanish River (disambigu ...

Texas
and eastern
New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Greater Albuquerque , OfficialLang = None , Languages = English English usually refer ...

New Mexico
. Most dry lakes are small. However,
Salar de Uyuni Salar de Uyuni (or "Salar de Tunupa") is the world's largest Salt pan (geology), salt flat, or Dry lake, playa, at over in area. It is in the Daniel Campos Province in Potosí Department, Potosí in southwest Bolivia, near the crest of the Ande ...

Salar de Uyuni
in
Bolivia Bolivia ; ay, Wuliwya ; Quechuan languages, Quechua: ''Puliwya'' , officially the Plurinational State of Bolivia, is a landlocked country located in western-central South America. The constitutional capital is Sucre, while the seat of g ...

Bolivia
, near
Potosí Potosí, known as Villa Imperial de Potosí in the colonial period, is the capital city and a municipality of the Department of Potosí in Bolivia Bolivia ; ay, Wuliwya ; Quechuan languages, Quechua: ''Puliwya'' , officially the Plurin ...

Potosí
, the largest salt flat in the world, comprises 4,085 square miles (10,582 square km). 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 A dune is a landform A landform is a natural or artificial feature of the solid surface of the Earth or other planetary body A planet is an astronomical body Astronomy (from el, ἀστρονομία, literally meaning the ...

dune
s can form. The
Racetrack Playa
Racetrack Playa
, located in
Death Valley, California Death Valley is a desert valley in Eastern California, in the northern Mojave Desert The Mojave Desert ( ; mov, Hayikwiir Mat'aar) is an arid rain-shadow desert and the driest desert upright=1.5, alt=see caption, Sand dunes in th ...

Death Valley, California
, features a geological phenomenon known as "
sailing stones Sailing stones (also called sliding rocks, walking rocks, rolling stones, and moving rocks) are part of the geological phenomenon in which rocks move and inscribe long tracks along a smooth valley floor without animal intervention. The movement ...
" 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 UC 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. The stones only move once every two or three years and most tracks last for three or four years.


Ecology

While a dry lake bed is itself typically devoid of vegetation, they are commonly ringed by
shadscale ''Atriplex confertifolia'', the shadscale, is a species of evergreen In botany Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterpri ...
, saltbrush and other salt-tolerant plants that provide critical winter fodder for
livestock Livestock are the domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction and care of another group to secure a more predictabl ...
and other
herbivore A herbivore is an animal Animals (also called Metazoa) are organisms that form the Animalia. With few exceptions, animals , , are , can , and grow from a hollow sphere of , the , during . Over 1.5 million animal have been —of ...
s. In southwest
Idaho Idaho () is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ''The State'' (newspaper), a daily newspaper in ...

Idaho
and parts of
Nevada Nevada (, ) is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ''The State'' (newspaper), a daily newspaper i ...

Nevada
and
Utah Utah ( , ) is a U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its so ...

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. ''
Lepidium davisii ''Lepidium'' is a genus of plants in the mustard/cabbage family, Brassicaceae. The genus is widely distributed in the Americas, Africa, Asia, Europe, and Australia.southern Idaho Southern Idaho is a generic geographical term roughly analogous with the areas of the U.S. state of Idaho Idaho () is a U.S. state, state in the Pacific Northwest region of the United States. It borders the state of Montana to the east and n ...
and northern Nevada. Far from major rivers or lakes, playas are often the only water available to wildlife in the desert.
Antelope The term antelope is used to refer to many species of even-toed ruminant Ruminants (suborder In biological classification, the order ( la, wikt:ordo#Latin, ordo) is # a taxonomic rank used in the classification of organisms and recognized by ...

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 A feedlot or feed yard is a type of animal feeding operation (AFO) which is used in intensive animal farming In grammar, an intensive word form is one which denotes stronger, more forceful, or more concentrated action relative to the root on which ...

feedlot
s and dairies. Results are erosion; fertilizer, pesticide and sediment runoff from farms; and
overgrazing Overgrazing occurs when plants are exposed to intensive grazing In agriculture Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentism, sedentary hum ...

overgrazing
. 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

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 The land speed record (or absolute land speed record) is the highest speed In everyday use and in kinematics, the speed (commonly referred to as ''v'') of an object is the magnitude (mathematics), magnitude of the rate of change of its P ...
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 The Bonneville Salt Flats are a densely packed Salt pan (geology), salt pan in Tooele County, Utah, Tooele County in northwestern Utah. The area is a remnant of the Pleistocene Lake Bonneville and is the largest of many salt flats located west of ...

Bonneville Salt Flats
in Utah and
Black Rock Desert The Black Rock Desert is a semi-arid region (in the Great Basin shrub steppe eco-region) of lava beds and playa, or alkali flats, situated in the Black Rock Desert–High Rock Canyon Emigrant Trails National Conservation Area, a silt playa n ...
in
Nevada Nevada (, ) is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ''The State'' (newspaper), a daily newspaper i ...

Nevada
have both been used for setting land speed records.
Lake Eyre Lake Eyre ( ), Dual naming, officially known as Kati Thanda–Lake Eyre, is an endorheic lake in east-central Far North (South Australia), Far North South Australia, some north of Adelaide. The shallow lake is the depocentre of the vast endorh ...

Lake Eyre
and
Lake Gairdner Lake Gairdner is a large endorheic salt lake in the Australia, Australian state of South Australia, to the north of the Eyre Peninsula. When in flood, the lake is considered the third largest salt lake in Australia. Description Lake Gairdner is ...

Lake Gairdner
in
South Australia South Australia (abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Austral ...

South Australia
have also been used for various land speed record attempts. Dry lake beds that very rarely fill with water are sometimes used as locations for air bases, for similar reasons. Examples include
Groom Lake Area 51 is the common name of a highly classified United States Air Force The United States Air Force (USAF) is the Atmosphere of Earth, air military branch, service branch of the United States Armed Forces. It is one of the eight unif ...
at
Area 51 Area 51 is the common name of a highly classified United States Air Force The United States Air Force (USAF) is the air File:Atmosphere gas proportions.svg, Composition of Earth's atmosphere by volume, excluding water vapor. Lowe ...
in Nevada, and
Edwards Air Force Base Edwards Air Force Base (AFB) is a United States Air Force installation This is a list of installations operated by the United States Air Force The United States Air Force (USAF) is the Atmosphere of Earth, air military branch, service ...
(originally known as Muroc Dry Lake) in California.
Brine Brine is a high-concentration solution of salt (NaCl) in water (H2O). In different contexts, ''brine'' may refer to salt solutions ranging from about 3.5% (a typical concentration of seawater, on the lower end of solutions used for brining food ...

Brine
s from the subsurface of dry lakes are often exploited for valuable minerals in solution. See, for example Searles Dry Lake and Lithium resources. Under United States law, a "playa lake" may be considered isolated
wetland A wetland is a distinct ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles ...

wetland
s, and may be eligible to enroll in the new wetlands component of the
Conservation Reserve Program Image:US-ConservationReserveProgram-20thLogo.svg, 175px The Conservation Reserve Program (CRP) is a cost-share and rental payment program of the United States Department of Agriculture (USDA). Under the program, the government pays farmers to ta ...
, enacted in the
2002 farm bill The Farm Security and Rural Investment Act of 2002, also known as the 2002 Farm Bill In the United States, the farm bill is the primary agricultural and food policy tool of the federal government. Every five years, Congress A congress is a f ...
(P.L. 107–171, Sec. 2101). The
Burning Man Burning Man is a festival A festival is an event ordinarily celebrated by a community and centering on some characteristic aspect of that community and its religion or cultures. It is often marked as a local or national holiday, mela, or M ...
yearly event takes place in a playa in the
Black Rock Desert The Black Rock Desert is a semi-arid region (in the Great Basin shrub steppe eco-region) of lava beds and playa, or alkali flats, situated in the Black Rock Desert–High Rock Canyon Emigrant Trails National Conservation Area, a silt playa n ...
in western Nevada every year.


Gallery

File:Devil's Golf Course in Death Valley NP.jpg, Devil's Golf Course in
Death Valley National Park Death Valley National Park is an American national park that straddles the California–Nevada border, east of the Sierra Nevada. The park boundaries include Death Valley, the northern section of Panamint Valley, the southern section of Eureka V ...

Death Valley National Park
, western United States Image:Lake Hart.jpg,
The dry lake and shore of Lake Hart, an
endorheic An endorheic basin (; also spelled endoreic basin or endorreic basin) is a drainage basin A drainage basin is any area of land where precipitation In meteorology Meteorology is a branch of the atmospheric sciences Atmospheri ...
desert lake in
South Australia South Australia (abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Austral ...

South Australia
.
Image:Jfader playa.jpg,
A closeup photograph of salt growths on the crust of a dry lake.
Image:EtoshaPan 2005-06 comparison.jpg,
Etosha pan The Etosha pan is a large endorheic An endorheic basin (; also spelled endoreic basin or endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water, such as river A river is a ...

Etosha pan
in northern
Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa Southern Africa is the south South is one of the cardinal directions or compass points. South is the opposite of north and is perpendicular to the east a ...

Namibia


See also

* * * *


References


Bibliography

* *John H. Wellington, ''Southern Africa: a geographical study'', Chapter 16 LAKES AND PANS {{Authority control Endorheic lakes Aeolian landforms Lacustrine landforms