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0157 Explorations in Turkestan 1903 : vol.1
Explorations in Turkestan 1903 : vol.1 / Page 157 (Color Image)

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[Photo] 95 A kettle-hole Lake on the Moraine extending from the Kurumdi Mass transversely into the Alai Valley. The Trans-Alai Mountains rising into the clouds.

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doi: 10.20676/00000177
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PHYSIOGRAPHIC OBSERVATIONS.   133

IN THE ALAI VALLEY.

With our field-glasses we had seen from Sari Tash the great glacier on Mount Kaufmann and large grass-covered moraines extending nearly across the plain from all the principal valleys along the Trans-Alai range.

The morainal masses extending transversely across the Alai Valley were each made up of at least two moraines belonging to two distinct, long-separated epochs. The old moraines are broad, smoothed-off lobes made up of large and small semiangular bowlders, usually of rather hard red limestone and mixed with finer till. Their surfaces sloped gently to the plain on each side, and no undrained depressions were seen. The whole was coated with loess usually 2 to 3 feet in thickness. The identification of this loess was at first a little doubtful, owing to the presence of thousands of marmot holes, most of which reached into the till below, thus bringing a quantity of small stones to the surface, but it was well established in exposures on stream cuts. The streams now flowing from the side valleys have

Fig. 95.—A Kettle-hole Lake on the Moraine extending from the Kurumdi Mass transversely into the Alai Valley.
The Trans-Alai Mountains rising into the clouds.

in some cases cut broad, flat-bottomed channels in these moraines and in other cases are deflected to one side, cutting a bluff.

Lying on the middle of these old smoothed-off moraines or in the channels there are long, narrower moraines of the second epoch. In topography they are made up of irregular chains of steep mounds with many large blocks on the surface and frequent kettle-hole lakes (fig. 95), and near their origins• are cut by sharp V-shaped torrent valleys. They seem to be made up of essentially the saine material as the old moraines. They also have loess on their surfaces and are grown over with grass, but, owing to their exceedingly irregular topography, their loess coat varies in thickness even more than that on the old moraines. It did not seem practicable with the little time I had to attempt to get an average measurement, but there appeared to be much more loess on the old moraines than on the new ones. Of course this might be partly due to the more exposed position of the latter. There seemed to be a third series of moraines extending a short distance from the valley mouths, and in cases overriding those of the second epoch (fig. 96). Professor Pumpelly considered them to be of a third epoch.