IIIFカラー高解像度
国立情報学研究所 - ディジタル・シルクロード・プロジェクト
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| IIIFカラー高解像度 |
| Southern Tibet : vol.7 | |
| 南チベット : vol.7 |
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引用情報
CHANGES OF CLIMATE.
295
facts he asks: how was this large lake formed: where would have been the outlet and is there any sign of a dam? Drew supposes the plain once drained to the Eastern Kara-kash, and later on it was dammed. »It is possible that at different times the dam may have been at different spots .... If, as is possible, the lake existed during part of the glacial period, then a glacier itself, with its moraines — perhaps a glacier occupying the head of Eastern Karakash Valley — may have formed the dam.»
In his résumé Drew gives the boundaries of the two basins and adds that to the north JOHNSON had shown »how the ridges and the valleys lessen in height till the plains of Khotan are reached». To the west was HAYWARD'S Kara-kash and high ground extending to the Kara-korum Pass and Suget-davan. To the east the country had never been explored. Drew thinks there is a bounding ridge of mountains on the east as there is one on the west. At the north-western corner of the basin of the lake or lakes he thus has an opening for former drainage between the Kwen-lun and the western ridge. This opening is now closed by alluvial accumulations. It was formerly probably obstructed to a much greater height than now, perhaps by glaciers and moraines, as glaciers at that time »were more numerous and larger than now». He also thinks a dam existed at the south-western corner.
From the highest margin-marks he finally draws the conclusion that at one time the whole Lingzi-tang and Kwen - lun Plains formed one great lake 6o by 2 0 miles and stretching to the very foot of the Kwen-lun Mountains. The subsequent sinking of the water and drying up of the lake he attributes to a change of climate. At a certain period of the desiccation the lake must have been separated into two parts.
Drew also visited some of the great Kara-korum glaciers.' In the Skardu tract he found lacustrine and glacial remains as GODWIN-AUSTEN and THOMSON had done before. He went up the Basha and Braldu streams. From Arundo he made an excursion and covered 31 marches on and alongside the glacier. At the irregular edge the ice seemed about 2 00 feet high, and higher up probably thicker. The lower end was r mile broad and covered all over with débris. The débris continued for some miles up. Still higher up clear ice appears between hills of moraine. Drew reached a point 2o or 25 miles from the end. He estimates the whole glacier at 3o miles.
As far as Drew could make out there was no possible way to the head of
the glacier and over the watershed. But he says:2
A way from Skardu to Yarkand used in former times to lead travellers for some distance up the Baltoro Glacier, and then across the range, here called Mustagh, by one of the northern tributary glaciers. From certain ice-changes that road becoming too
I Op. cit., p. 364 et seq. ., Op. cit., p• 370.
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