252 PHYSIOGRAPHY OIL CENTRAL-ASIAN DESERTS AND OASES.
It is an undrained depression 20 miles in diameter, with a lake S miles wide nearly divided by two hilly peninsulas of ledge rising from the sediments of its northern and southern shores. Whether it is wholly the result of moraine damming or in part a genuine structural basin is not certain. The bottom of the eastern half of the lake slopes as a continuation of a 3-mile-wide belt of abandoned sediment on that side, to a depth of only 50 feet near the peninsula. But a deep trough of 700 feet of water with steep ledge shores forms its western half and appears to be a continuation of a narrow gap in the mountains to the south. The inclosing mountains are of granite and highly tilted shales and crystalline limestones, while the peninsula is of granite and vertical slate. We are dealing with the core of an ancient mass.
Kara Kul is a lake of bitter salt water. Its sloping shores are white with salt accumulated into low ridges, where the brine from each wave wetting has dried out after the recession. And behind some of these there are lagoons of
Fig. 432.—A Granite Ridge at Kara Kul (showing the secular Deflation of the Pamir).
brine, collected from the overflow of large waves, thus extending the white salt belt ioo feet or more on shore. During summer there are ducks and water-fowl that feed on the wide-bladed slimy grass growing in shallow water.
On this high desert no man lives, and those who cross by caravan have difficulty in finding fodder and water, as but little grass is found below the watercourses on high moraines, and even larger streams are dry by day. It is io o'clock at night ere the glacial water melted by day has accumulated and reached the steppes to run off before sunrise. A few small areas of thin, scattered wire-grass are found in shallow depressions near the lake, and a scrubby desert weed with long roots serves for fuel. Otherwise, the plain is void of life in summer. During winter large herds of Ovis poli, the great-horned wild sheep for which Kara Kul is famous, descend from their snow-bound mountains, to hunt for these rare bits of grass. By summer they live with the rabbits and marmots high up under
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