A playa (or pan) is a dry or ephemeral lakebed, generally extending to the shore, or a remnant of, an
endorheic lake. Such flats consist of fine-grained sediments infused with alkali salts. Playas are also known as alkali flats, sabkhas, dry lakes or mud flats. If the surface is primarily saltthen they are called salt pans, salt lakes or salt flats.
Their surface is typically dry, hard and smooth during the dry season, but wet and very soft in the rainy season. Playas may be small, round depressions in the surface of the landscape. A
playa lakeis formed when rain fills this hole with water, creating a small lake. Playas can also form when the water table intersects the surface and water seeps into them.
Playas are typically formed in semi-arid to arid regions of the world. The largest concentration of playa lakes in the world (nearly 22,000) is on the southern High Plains of
Texasand eastern New Mexico. While most playa lakes are very small, other examples of playa lakes include Lake Alablab in Suguta, Kenya, and Wild Horse Lake, Oklahoma, USA. Salar de Uyuniin Bolivia, near Potosí, is the largest salt flat in the world at 4,085 square miles (10,582 square km).
Many playas contain shallow lakes during the rainy season, especially so during wet years. If the layer of water is thin and is moved around the playa 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. Very little water can result in dune formation.
Racetrack Playais a place in Death Valley National Park, very famous for its ' sailing stones', rocks that mysteriously move across its surface.
While the playa itself will be devoid of vegetation, they are commonly ringed by
shadscale, saltbrushand other salt-tolerant plants that provide critical winter fodder for livestockand other herbivores.
Threats to playas include pollution from concentrated animal feeding operations such as cattle
feedlots and dairies, erosion, fertilizer, pesticide and sediment runoff from farms, and overgrazing.
The extremely flat, smooth and hard surfaces of playas make them ideal surfaces for
motor vehicles and bicycles. Large-sized playas are further excellent spots for pursuing land speed records, as the smoothness of the surface allows low-clearance vehicles to travel very fast without risk of disruption by surface irregularities, and the trajectory need not be precise to avoid obstacles. The playas at Bonneville Salt Flatsin Utahand Black Rock Desertin Nevadahave both been used for setting land speed records. Dry lake beds that do not fill with water at any time are sometimes used as locations for air bases, for similar reasons. Examples include Area 51in Nevada, and Edwards Air Force Basein California.
The Spanish word "playa" (IPA2|ˈplaʝa) literally means "
beach". Alkali flats are known by this name in some parts of Mexicoand the western United States(pronEng|ˈplaɪə). On the Llano Estacadoand other parts of the Southern High Plains, "playa" refers to a playa lake, a smaller seasonal depression.
"Pan" is the term used in most of southern Africa. These may include the small round highveld pans, typical of the
Chrissiesmeerarea, to the extensive pans of the Northern Capeprovince, which are sometimes employed for land speed record attempts.
In Arabic, an alkali flat is called a "
sabkha" (also spelled "sabkhah", "subkha" or "sebkha") or "shott" (" chott").
Central Asia, a similar "cracked mud" salt flat is known as a takyr.
* cite journal
last = Briere
first = Peter R.
year = 2002
month = May
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
accessdate = 2008-05-20
* [http://www.lbk.ars.usda.gov/wewc/biblio/bar.htm The Bibliography of Aeolian Research]
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