SOUTHERN PACIFIC LINES 251 
Within two and one-half years after the Salton Sea was flooded its 
water was four times as saline as that of the river from which its water 
was derived. When the water receded and revealed a portion of the 
bottom of the basin it was found that several feet of silt covered the 
old salt deposit on its floor. 
It has been estimated that during the time of their overflow into 
the Salton Basin the Alamo and New Rivers removed from their beds 
and banks 450,000 cubic yards of material in nine months. At this 
time the Alamo River developed a waterfall 30 feet or more high, 
which for a while cut backward at the rate of 1,400 feet a day. 
Outside of the irrigated area this basin is part of the most arid 
desert in the country. It was called by the Mexicans and Indians 
‘Lia Palma de la Mano de Dios” (the hollow of God’s hand) and was 
named the Colorado Desert by W. P. Blake in 1853, eight years 
before the State of Colorado was named. At present the name 
Imperial Valley is used for the eastern part of the area, Salton Basin 
for the central area, and Coachella Valley for the upper part from the 
head of Salton Sea to the foot of San Gorgonio Pass. It is an inland 
extension to the northwest of the valley that holds the head of the 
Gulf of California and comprises more than 2,000 square miles between 
the Santa Rosa Mountains and Peninsular Range on the southwest, 
and the Chocolate, Orocopia, and Little San Bernardino Ranges on 
the northeast. It is followed for more than 150 miles by the Southern 
Pacific Railroad. 
Structurally this area is a complex downfaulted block of the earth’s 
crust, deeply floored by Tertiary sediments and alluvial deposits. 
Its lowest part is now 273.5 feet below sea level. Its main outlines 
apparently were developed in Tertiary time, for it contains extensive 
deposits of Tertiary age, and these have been flexed and faulted. 
They comprise Miocene or Pliocene marine beds, overlain by subaerial 
beds that were formed in a desert basin somewhat like the present one. 
Since that time, however, the basin has been greatly uplifted, for part 
of the Tertiary strata have been eroded down to a level far below the 
present valley bottom. It has been suggested that the basin was 
occupied until recently by an extension of the Gulf of California, 
which was cut off by the building of a delta by the Colorado River, 
but recent investigations seem to indicate that much of the present 
depression below sea level was effected by crustal movement after 
most of the Colorado River delta was built, and therefore long after 
the invasion by the sea. Blake discovered that in relatively recent 
time the basin was occupied by a transient fresh-water lake of large 
extent, which he called Lake Cahuilla (ca-wee’ya). (See p. 253.) 
The delta cone of the river, which now cuts off the basin to the south- 
east, is young, however, and its top is only about 30 feet above sea 
level. That there has been recent faulting in part of the basin is 
