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0219 Explorations in Turkestan 1903 : vol.1
Explorations in Turkestan 1903 : vol.1 / Page 219 (Color Image)

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[Photo] 133 Marble Bowlders, and beginning of the Gorge associated with the fourth Khoja Ishken Glacier.

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doi: 10.20676/00000177
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RECONNAISSANCE IN CENTRAL TURKESTAN.   189

The two upper gorges of the Khoja Ishken Valley and part of the lower are cut in a metamorphic limestone which sometimes becomes marble, and in each the grade is so steep that the stream is still actively cutting downward. Hence the width of the gorges relative to the size of the stream gives a good measure of the time that has elapsed since each gorge was formed. The upper gorge, the one associated with the fifth moraine, is exceedingly young ; so young that though it is cut to a depth of over 5o feet in solid rock it has scarcely widened at all, and the top is but slightly wider than the bottom (fig. 132). It is so narrow in one place that it has twice been naturally bridged by bowlders. One of these bridges is utilized by the road ; the other is a great granite bowlder, 25 or 3o feet in diameter,

Fig. 133.—Marble Bowlders, and beginning of the Gorge associated with the fourth Khoja Ishken Glacier.

which lies directly across the narrow slit cut by the stream. The next gorge (fig. 133), belonging to the fourth moraine, though not much deeper than the upper one, is decidedly wider both relatively and absolutely, as shown by the accompanying cross-sections (figs. 134, 135). In spite of the fact that it is cut in marble somewhat harder than the limestone of the upper gorge, its sides have a slope of about 45° instead of nearly go°. In one place it shows a little terrace near the bottom. It seems to be two or three times as old as its successor. The gorge of the third moraine, which is the oldest and the farthest downstream, is so broad that the road runs at or close to the bottom, and the sides have a slope of only 25° or 3o° even where it is cut in granite or slaty quartzite. The terrace, which lies zoo or 300 feet above the stream, has been consumed to a mere fringe on the valley-side, and