280 PHYSIOGRAPHY OF CENTRAL-ASIAN DESERTS AND OASES. 
and received a thick coat of loess mixed with talus. Directly in front both valley 
sides come down to the flood-plain in this fashion. ‘Time enough has elapsed for 
accumulation of huge deltas and gradual loess-mixed talus-cones, some of them 
truncated by the river, and the cutting-down of tributary once-hanging glacier 
valleys to sharp V-sections and canyons on a regular grade to the river since any 
time when the ice was farther forward than now. As an exception to this it may 
be said that the glacier is at present in the process of a minor oscillation that makes 
it about 200 feet short of a cross-ridge of moraine deposited probably some few 
years ago. 
Owing to the depth of its gorge and alpine character of surrounding mountains, 
the Zerafshan glacier, unlike those of the Trans-Alai and Pamir, is wholly covered 
with moraine longitudinally banded with the various colors of its different tribu- 
tary glaciers. But the most significant difference between it and those others 
lies in its being the only one that yielded no evidence of more than one expansion 
greater than the present. If the old moraine found half-buried in the alluvial 
terraces down to 45 miles below the present ice belongs, as seems most likely, 
to our second epoch, it is easy to understand how that of the first epoch was washed 

Fig. 458.—The Zerafshan Glacier. 
away by the river during the latter part of the second and early part of the third 
cycle of erosion. It is not so easy to understand how the fourth erosion cycle 
could have obliterated third- and fourth-epoch moraines without obliterating that 
of the second epoch. Indeed, it seems impossible under the conditions involved. 
There remain two alternatives: either local conditions were such that little if any 
expansions took place, or the present glacier is greater and obliterates them. But 
since the glacier is now less than 15 miles long, it seems necessary to assume that 
there were local reasons why no considerable advance corresponding to those of the 
third epoch of Trans-Alai and Pamir took place. It seems quite likely that our 
fourth-cycle uplift of the Zerafshan glacier and its surroundings took place after 
the third glacial epoch farther east, where glacial conditions may have been acceler- 
ated by uplift during or before that epoch. The Zerafshan is now much more 
actively cutting down than any other large stream met with, and its glacier is 
advancing* as though the uplift were still in process and accelerating glacial con- 
ditions also. 

* Excepting the minor oscillation of recent years. 
