THE ZUNI SALT LAKE 187 



The Indians have utilized this source- of salt for many centuries and 

 regard the lake with great veneration. 



There is a large amount of salt in the lake and springs. An 

 average of about three tons a day is produced by very crude methods ; 

 it is valued at from $2 to $2.50 a ton. This industry sustains the 

 small settlement of Mexicans. 



The origin of the salt is believed to be in springs which rise under 

 the water near the south end of the lake. If the water from these 

 is not saturated with salt, the percentage increases by the great evap- 

 oration in this arid region. Undoubtedly it is derived from the under- 

 lying Red Beds, which have the relations shown in the cross-sections. 

 These Red Beds outcrop at no great distance, and yield salt springs 

 at some points. A small amount of fresh water flows into the lake, 

 partly from a small spring on the east shore, which flows constantly, 

 and partly from scanty rains falling directly into the depression, 

 or running into it from a small drainage area lying mainly on the 

 high slopes south. Although no deep borings have been made, 

 the depression appears to contain a salt deposit of considerable 

 thickness, mixed with small amounts of mud washed from the sur- 

 rounding slopes, and dust carried by the wind. Apparently the lake 

 occupied the entire floor of the depression at one time, but, by evap- 

 oration and the deposition of mud, it has greatly diminished in size; 

 doubtless the lake has been crowded over to the north side of the 

 depression because the greater amount of detritus is deposited on 

 the south side. 



In the map and cross-sections of Fig. 2 are shown the principal 

 features of the salt lake depression, and the photographs reproduced 

 in Figs. 3-5 show the lake from three points of view. 



The depression is in a plain sloping gently northward on the south 

 side of the Carrizo Valley. A short distance to the south rises a line 

 of cliffs of Cretaceous sandstones, in part capped by lava, while 

 there is a corresponding ridge several miles north on the opposite 

 side of the valley. The floor of the valley is Cretaceous sandstone, 

 overlain in places by lava flows, one of which forms part of the upper 

 wall of the northern, eastern, and southeastern sides of the depression. 

 All about the margin of the depression there is a widespread mantle 

 of fragmental material, mostly volcanic, which thickens toward 



