30 THE SALTON SEA. 



particles are somewhat weathered and are much more uniform in size. Practically all the 

 soils of the Delta are silts or very fine sands. They are agriculturally excellent and form 

 the very productive fields of the Imperial Valley. Aside from "alkali" (which will be 

 discussed in a moment) their chief fault is too great heaviness and difficulty of working, 

 due to their fine texture. True clays, however, are practically unknown. 



The soils of the beaches of the Salton Sea all come within the two classes mentioned. 

 About the northwestern two-thirds of the Sea's periphery the soils are of the desert, mountain- 

 wash type. Nearly everywhere they are sandy and gravelly, but there are two localities 

 where important areas of silt are found. The first, and by far the larger, is at the extreme 

 northwestern end of the Sea and has been formed by the flood-waters of Whitewater Creek. 

 For perhaps 5 miles along the edge of the Sea, westward from a point southeast of Mecca, 

 the shore-line is silty and muddy. Beyond this to the west and south one encounters the 

 sandy outwash of the Santa Rosa Mountains. The other silty area is much smaller and 

 occurs in the valley of Carrizo Creek between the southern end of the Santa Rosa Mountains 

 and the Superstition Mountain uplift. The soils are similar to those of the Mecca region, 

 but are somewhat more sandy. 



Over the southeastern third of the Sea's periphery the soils are of the Delta type and 

 are very heavy and muddy. Everywhere the slopes of the beaches are very slight and the 

 mud is usually so soft that landing from a boat is very difficult if not impossible. Toward 

 the north, soils of this type extend along the beaches as far as the railway station of Lano, 

 where they merge with the sandier soils derived from the outwash of the Mud Hills to 

 the north. Indeed this merging of Delta and outwash material extends considerably to the 

 southeast, and is noticeable perhaps as far as half-way from Lano to the mouth of the 

 Alamo River, though the Delta material predominates through nearly all of this distance. 

 On the southern side the Delta soils extend a lesser distance, being separated from the 

 Carrizo Creek silty area above mentioned by about 10 miles of somewhat sandy soils 

 produced by the outwash from Superstition Mountain. During the present submergence 

 the area of the Delta soils has been somewhat extended along the beaches by the silt poured 

 into the Salton Sea and distributed by it. It is probable also that the submerged soils 

 near the mouths of the New and Alamo Rivers have received considerable vertical incre- 

 ments of river alluvium. (Plate 8 b.) 



So far as their physical and mineral nature is concerned the soils of all the beaches are 

 likely to be of very high fertility. Their only fault is the frequent presence of "alkali," 

 this being the accumulation in the surface layers of excessive amounts of soluble salts, 

 mainly chloride and sulphate of sodium. The natural accumulation of these salts is 

 exclusively a desert phenomenon and is due to the natural movement of water through the 

 soil being too slight to remove the salts freed by chemical decay of the soil minerals. The 

 water of the infrequent showers penetrates a few inches into the soil, dissolves the salts 

 it finds there, and, when the shower is over, returns to the surface by capillary action 

 and evaporates, leaving the salts it has brought up from below. Desert soils that are fine 

 enough in texture to permit capillary rise of water through them are nearly always more 

 or less "alkaline." In sandy soils, the forces of capillarity are so weak that rain-water 

 can not reascend to the soil surface and must continue its downward journey to stream 

 channel or underflow, taking its dissolved salts along. Sandy soils are never alkaline 

 unless the natural drainage is for some reason insufficient. In general, on all the Salton 

 beaches, the silty soils are more or less alkaline; the sandy soils are never so, except for 

 some local reason, such, for instance, as the rise of underflow to the surface. 



The submergence of the soils by the waters of the Salton seems to have had sur- 

 prisingly little effect upon their alkali content. On the Salton beach just southwest of 

 Imperial Junction is one of the "observation stations" described elsewhere in this volume 

 by Dr. MacDougal, and the soils of the area have been studied by the writer since their 



