THE PANGGONG LAKES A GIGANTIC RIVER. 521
The Panggong Lakes have a length of no less than 155 km., while the breadth is at many places only 1,2 km., at the most 5,6 km., and as an average 2,4 km. They are much more like a gigantic river than a series of lakes. Day after day you travel along their northern shores to the west and N. W., and at every rocky promontory you have a new splendid view of narrow water between the mountains in front of you. During my journey in 190I I considered them only a series of lakes, and I got the same impression as HUNTINGTON that their long bed in the valley was due to glacier action. But having seen neighbouring parts of the Indus valley at the end of 1907 and having studied the problem, I feel perfectly convinced that the Panggong Lakes are a river whose water has been dammed up by secular movements of the surface in connection with the rise of the mountain ranges, and that thus the theory of OLDHAM must be correct. There has been either a regular upheaval of the ground which was greatest in the west and which gradually diminished to the east leaving the region around Noh and Tso-nyak nearly untouched, or a sinking of the ground with its maximum in the east around Noh, and leaving the region of the threshold between the lake and the Drugub river unmoved. It seems improbable that the rise of the ground should have been a local phenomenon taking place only where the threshold is now situated , for then we should expect much greater depths in the western part of the Panggong-tso. My two sounding lines across the Panggong-tso proper started, the one from my Camp CXLV towards the S. 65 ° W., and the other from Camp CXLVIII towards the S. 26° W. The deepest point on the former line was 4o m., and on the latter 47,5 m., both nearly in the middle of the lake and at a distance of 25 km. from one another. The second line was at a distance of 17 km. from the western end of the lake, so very possibly the bottom of the lake basin may sink some meters to the N. W. before the definite rise begins towards the N. W. end of the lake and further to the threshold. Accepting, however, the 47,5 m. as the greatest depth of Panggong-tso, we find that the bottom of the valley, from the eastern shore of the Tso-nyak to this point sinks only 47,5 m. in a distance of 138 km. Taking a section of the neighbouring Indus we only need to travel 46 km. to find a sinking of 5o m., viz., from my Camp CCLXI, Na-gangkal, 4229 m. high, to Camp CCLXIV, Lungkung, 4179 m. high.
Of course, the ground of the lake basins does not fall regularly from east to west, though as a rule the depth increases in that direction, and the deepest point measured in Panggong-tso is 16 m. deeper than the deepest point in Tso-ngombo. At four places between the different lake basins, the ground of the valley even rises above the surface of the lakes. Here DREW'S theory of the talus fans may no doubt be of use.
Gar-gunsa is at an altitude of 4287 m., Lungkung at 4179 m., both are situated in the straight Gartang-Indus valley and at a distance of 140 km. from one another;
66. VII.
IIIFカラー高解像度
