CHARACTERISTICS AND DISTRIBUTION OF LAKES 555 
and the other in south-eastern California, the arid floors of the 
deserts descend 300 feet beneath sea-level. An outflowing branch 
of the Colorado in time of flood occasionally turns northwards 
on reaching the delta, and flows into the latter depression, forming 
a short-lived lake. Sometimes the valleys are filled for a thousand 
feet or more with rock waste ; some of the gently inclined slopes 
Sarthahmef Cdio' 
Fig. 66. — Inland drainage areas of the Great Salt Lake region, Central America, 
and Mexico ; showing also the Mississippi River basin. 
[The inland drainage areas are stippled.] 
at the foot of the mountains are rock-floored, bearing only a thin 
veneer of waste here and there. The streams issuing from the 
mountains after a shower find no channels, but spread out in a sheet 
a mile or more broad and I or 2 feet deep, washing the gravel veneers 
forward down the inclined rock-floor ; this peculiar style of drainage 
has been termed a " sheet flood."' Many small streams from the 
mountains dry up on the waste slopes, owing to the great evaporation ; 
the larger ones unite to form shallow salt lakes in the lowest part of 
the troughs lying between the mountains. Others form shallow 
