RECONNAISSANCE IN CENTRAL TURKESTAN. 
203 
TERRACES AS A RESULT OF WARPING. 
There seem to be but two causes competent to produce terraces of so wide a 
distribution and so uniform a character. One of these is warping of the earth's crust 
and the other is change of climate. It is highly probable that terraces resulting 
from both causes may exist close together, but in the main the terracing in Central 
Turkestan seems to be due to climatic variations. The reasons for this conclusion 
are, first, the wide distribution of the terraces, and, second, their relation to the 
deposition of gravel. 
Fig. 140. - View down the Kuzzil Su on the eastern border of Bokhara, showing a 
gravel-filled valley which has been re-excavated. In the foreground four terraces 
can be seen on the left. 
A phenomenon of so wide an extent and ot such uniformity in essential features 
as are the terraces must have a proportionately extensive and uniform cause. It is 
possible to imagine a complicated and intermittent bending of the earth's crust so 
extensive and so systematically rel.ited to the streams that all portions of a large 
area containing four or five distinct and interlocking river basins, with streams 
flowing in every direction, should be warped so as to cause everv stream to cut 
terraces of the same .sort and in the same order. But this would involve a more 
highh- specialized type of bending than is known elsewhere. It would require that 
