DESERTS. 281 
The Zerafshan River is one of the few black rivers of Central Asia. Most 
of them are red from the gypsiferous beds folded into all those ranges; oxidized 
sediments apparently deposited under arid conditions similar to the present. 
Its charge of black stuff comes from the black slates and shales around its glacier, 
from which fully two-thirds to half its water springs. One of the most striking 
facts about the river is the increase of volume up- instead of downstream, because 
after about two score miles from its source more water is lost by evaporation than 
is gained from tributaries. Therefore, most of its sediment is glacier-ground stuff 
directly from the ice-cave, the rest from tributary glacial streams taken in a few 
Berg - schrund 
——— N<—__—___—— 





Valley side—— 
of loess slope— 

Glacier ice 


covered with moraine 




eae Og 
eee NOE 
ee IL TO ag 7 Da. 
ae) | SY alee ar 
SS) VA Re ge 
SS Vqa0s7e vols 
ee VAG = edt ey iy S ~~ zs 
a Sy oa O° ¢=—,.**hy 7_—~ 
a ae NA aes r =2%y 7 eB °Go O5 CAs 
— aks Qep tte ilies Tie g 
—— =~ . Soae oy, B25 * 0% °9 
fea, ae aear \Q een 2 oP 35 A S9.2% N\ 7 
SN = 
Se ~o 2 Ose =2 09007288 
eases ae, WO CO ea SLES eo °S3 Ft 
= g. SSS ces \\\ 
——— Alluvial eee \ 
oy 
TTI, 
= cobble plain 

fo) Via, V2 mile 
Fig. 459.—Sketch-map of the End of the Zerafshan Glacier (R = Recession). 
miles below, and that from cutting-down of its channel. It may therefore be 
assumed that in total its deposits throughout glacial time till now are mostly of 
glacial origin, and that the loess derived from it was mostly fine stuff of glacial 
grinding. In fact, one may attribute a large part of Central Asia’s loess to wind- 
work over the flood-plains of glacial alluviation, especially those of earlier epochs. 
The loess steppe of Samarkand has been warped up into a dome about 40 
miles across and 1oo feet high in the middle and dissected by old distributaries 
and irrigation canals of the Zerafshan, some of which, notably the Dargum (fig. 461), 
cross and join again beyond. ‘The interesting structure thus exposed in clean sec- 
tions up to 100 feet in height reveals an interlapping of pure loess of vertical cleavage 
