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0224 Explorations in Turkestan 1903 : vol.1
Explorations in Turkestan 1903 : vol.1 / Page 224 (Color Image)


[Figure] 137 Cross-section of the Kan Su Valley at an elevation of 11, 000 feet.

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doi: 10.20676/00000177
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of Kan Su. It shows something of morainic topography, although this is not very marked. The slopes are thoroughly graded and covered with grass, and the moraine as a whole is cut by several subparallel valleys, two of which are occupied by streams and have slightly terraced sides, while the others are abandoned, and seem to be stream channels of glacial times. Their heads are abruptly cut off by the fourth moraine, which lies at an elevation of about 9,500 feet, where there is a sudden rise in the valley floor, and where the main valleys which are not beheaded contract somewhat. At the top of this rise lies the distinct frontal ridge of the fourth moraine, horseshoe-shaped and inclosing a depression. The rest of this moraine has a pronounced glacial topography, although the slopes are perfectly graded. Moraines Nos. 3 and 4 appear to be of different but not widely separated ages. The vegetation of both has reached what may be called the stage of complete occupation; that is, they are covered with a fine growth of grass, except in the valleys, where there are some trees. The fifth and last of the old moraines, on the contrary, has not reached this stage. It begins at an elevation of io,ioo feet, where there is a sudden change to very rough moraine topography, which seems to be of considerably later date than that on which it lies. Instead of the surface being smooth and grassy and almost free from stones, the rough slopes are covered with angular fragments of rock, among which are scattered cedar trees and a growth of thin, weedy grass quite unlike the turf below. The bowlders, too, are larger, more numerous, and more angular than those of the other moraines. The difference between this fifth moraine and its predecessor is more marked than that between the adjacent older moraines. The present moraine at an elevation of 10,500 feet is quite as sharply distinguished from the fifth as the fifth is from the fourth, and the change is of the saine sort. The present moraine exhibits in many places a sharp line of division, above which the rock waste is even more angular and fresh than below, and above which there is practically no soil filling the interstices of the rock and hence absolutely no vegetation. Much of the moraine lies as a cover on the ice itself.

In its lower portion the modern moraine spreads out, so that for a short distance it fills the whole width of the valley. Higher up, however, the moraine, or

rather the glacier itself with a covering of moraine, lies in an inner valley

cut in moraine stuff of an older date.

This is represented in the accompanying cross-section through the

valley at an elevation of about i 1,000 feet (see fig. 137). The portion A rep-

resents the rock valley composed of A_rock walls of valley. B=moraine of third or fount

epoch. C=modern glacier. D=modern moraine. Di—bit

limestone below and purple slate   of modern moraine which has overflowed B.

above ; B represents an older moraine,   Fig. I37.—Cross-section of the Kan Su Valley at an elevation

either No. 3 or No. 4, which was

of 11,000 feet.

formed so long ago that its slopes are thoroughly graded and are well covered with grass, and bowlders have almost disappeared. Yet it is not so old but that it still retains signs of a morainic topography, though this is so far destroyed that the