The Mojave Desert 125 



Playas or "dry lakes" are widely distributed throughout the 

 desert region. It is somewhat paradoxical to speak of a "dry" 

 lake. Often flat dry surfaces of saline mud are ripple-marked 

 from the wind before the water disappeared. Seen from a dis- 

 tance such "dry lakes" may deceive the traveler, the dry flat 

 bottom having the appearance of a water surface. The term 

 "dry lake" seems therefore not entirely inappropriate. In the 

 desert region the rainfall is very light, but sporadic. Mountain 

 torrents tear down the slopes with great erosional force after 

 sudden rains. Broad basins between mountain ranges are 

 generally filled, often to depths of hundreds of feet, with al- 

 luvial wash from the surrounding mountains. In the lowest 

 parts of such basins water may gather after storms, and large 

 areas may be covered by shallow sheets of water for a time. 

 Soon, however, the waters disappear by evaporation, and the 

 lowest part of the basin becomes a salt-incrusted flat pan, or 

 dry lake. 



Salt Deposits Acc^un^date on Lake Bottoms 



Scores of dry lakes or playas range in size from a few acres 

 to lake beds several miles across. One of the largest and most 

 important playas is Searles Lake, which has an area of about 60 

 square miles. This playa is important because of the extensive 

 deposit of crystalline salt in the central part of the broad basin. 

 Solid salt beds embrace an area of 11 or 12 square miles, and 

 extend to depths of 60 to 100 feet. It is unique in that the salt 

 is nearly pure crystalline mineral (sodium chloride), and not 

 interbedded or mixed with dust or clay, as is the case in many 

 playas where saline deposits occur. This deposit of salt is free 

 from earth sediments, it is thought, because of settling basins 

 in Indian Wells and Salt valleys through which waters passed 

 from Owens Lake during Quaternary (Pleistocene) time when 

 waters from Owens Valley evaporated here. 



Death Valley contains an immense salt field. It extends 

 fully 30 miles south from the old borax works. It varies in 



