Dry lakes dominate a number of semiarid world landscapes. There is no generally accepted technical designation but many regional names with different linguistic roots: playa lakes (Mexican, Spanish), alkali or salt flats (American English), sebkha (French, Arabic), pan (Afrikaans), and so forth. Pans in enclosed basins tend to be elliptical and hold water seasonally or after sporadic heavy rains. Typically floored by

clays, they are infused to varying degree by salts of several kinds. While the episodic waters are fresh they attract a myriad of insects, birds, ungulates and people in ecological succession, and the waters recharge shallow aquifers that may promote clusters of hygrophytic vegetation such as sedges, reeds, true grasses, cattails and salt brush. As the waters evaporate and turn brackish, or are infected with botulism (Dr. Richard Liversidge, pers. comm.), antelopes or cattle stop visiting, leaving only salt brush and hardy animal forms burrowing in the mud. Sodium salts settle out or effloresce on the faces of contacting sediments.