Playas

The word playa comes from Spanish and translates into English as “shore” or “beach.” As early as the late 1800s, however, the term playa was adopted for use in geomorphology in reference to the ephemeral lakes in the Great Basin of North America. To complicate things, playa is not the only name applied to these features, and names vary geographically, sometimes even at the local scale. Terms that are used more or less synonymously with playa in North America include playa lake, playa-lake basin, prairie pothole, buffalo wallow, rainwater basin, lagoon, salt pan, salt lake, alkali lake, bolson, and dry lake. A variety of names come also from other parts of the world, including vlor (Southwest Africa), sebka (North Africa), kewire (Iran), sabkha (Middle East), rei (India), praia (India), plage (France), pliazh (Russia), salar (Chile), boinka (Australia), and salina (Spain and elsewhere). Though geographers and other Earth scientists have not yet completely agreed on a term, playa and playa lake are the most commonly used. Similarly, a wide range of definitions for playa exists in the literature, but one can reduce the myriad definitions to something relatively simple: an internally drained basin that is flat, barren, or sparsely vegetated, formed in prairie to desert environments and infrequently containing either freshwater or saline water. Though many have defined playa with a requisite diameter measuring hundreds of meters, many functioning playas are 100m or less in diameter (see High Plains photo).

In North America, playas are ubiquitous on the High Plains of the Great Plains, but many also occur throughout the intermountain western region. Within the southern and central Great Plains, where playas are densest, estimated numbers range from about 25,000 to more than 40,000. Several origins have been proposed for these playas, but those most commonly cited are subsidence as a result of dissolution of subsurface salt or carbonate beds, the collapse of piping (conduits created by percolating water), eluviation (the downward movement of particles or dissolved solids), deflation, or various combinations of the preceding. Of these, deflation is frequently identifiable as having at least a partial role in playa development, in that on the downwind side of many playas, crescent-shaped dunes (lunettes) of clay-to sand-size material have accumulated (see lunette photo). Because of their characteristic location on the south to southeast side of the playa basin, lunettes in the High Plains likely developed during the last glaciation, when prevailing winds were from the north and northwest.

Playas are crucial to the ecosystems in which they occur. In the Great Plains, playas function as sources [Page 2200]of recharge to the High Plains aquifer, as wetland habitats for migratory waterfowl, as water sources for animals (wild and domesticated), as biogeographic islands for native wetland vegetation, as carbon sinks, and as sites for the breakdown of agrochemicals. Throughout history, playas have served humankind as oases, first for the Paleoindians and subsequently for the early European settlers.

Small playa within a winter wheat field on the High Plains

Source: Author.

View northeast of playa and associated lunette. The lunette, accentuated by a contour field terrace, is visible in the lower right of the image.

Source: Author.

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