144 EXPLORATIONS IN TURKESTAN. 
surface increase gave enough evaporation to equalize the influx, or till it reached an 
overflow. Whether these wet periods were or were not coincident with the glacial 
advances remains to be pro\-ed. Since the annual range of temperature is here so 
low that it freezes nearh- every night even on the lowest steppes aljout Kara Kul, 
it is natural to feel that a sufficient increase of precipitation is all that is needed for 
a glacial advance, and that the glacial epochs of the past were brought about by the 
same wet periods which raised the surface of the lake. The only fallac}' here is 
tliat there might have been a wet period raising the lake level, but during which 
the annual temperature was so high that not enough snow would have accumulated 
to bring about a glacial advance. 
Perhaps the most extraordinarj- circumstance about Kara Kul is that it is said 
to overflow occasionally, although it is so strongly saline that long stretches of its 
shores are coated to a thickness of 2 to 3 feet with salt. Severtzoff" states that 
during high northerly stonns the water is driven up in the long southern arm, over- 
flows into a branch of the Murg-ab, and thence into the Amu dar^a. 
Fig. 109. — Drowned Valleys on ihe wesl side of the North Peninsula. Looking north to the Trans- Alai range. 
Unfortunately, we did not have time to visit the southern divide. It seems 
ver}" likely that it was blocked by moraine during the high expansions of the lake. 
A moraine during the earlier epoch might have dammed and raised the lake to the 
high levels marked by old worn-down terraces. During the long time intervening 
between the two advances it might have been cut down by overflow and other 
erosion and again raised by the overriding moraine of the later epoch. This 
reasoning would make the lake expansions coincident with the glacial advances. 
It is, however, complicated by the lowness of the northern divide over the Kara 
Jilga moraine, but Kotir Kul is, by Russian leveling, 600 feet above Kara Kul, and 
the divide at least 200 feet above that. Without the great overriding moraine this 
divide would be several hundred feet lower, so that Kara Kul may have had two 
outlets during the earlier glacial epoch, if it was during that epoch that the lake 
rose to the 200-foot or higher levels of the old terraces. There has, however, been no 
overflow over this northern divide since the falling into place of the overriding 
moraine, for its topography is unaltered. 
Tlie northeni peninsula rises abrupth' from deep water on the west, and more 
gradually from the shallow water and lake sediments on the east. Its western shore 
is indented with deep bays, from which rise steep spurs of rock as islands. The 
