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 |
| Scientific Results of a Journey in Central Asia, 1899-1902 : vol.2 | |
| 1899-1902年の中央アジア旅行における科学的成果 : vol.2 |
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| 砂砂漠上のタリム川の成り行き。Effect of the Tarim upon the sandy desert. |
引用情報
336 THE LOP-NOR PROBLEM.
existing data, but by the evidence of the Chinese maps? There can be no doubt that south of the lowermost Tarim (= Kuruk-darja) there extended a »sea of sand» similar to that which at the present day is found everywhere along the south side of the Tarim. South of the lake of Lop-nor the country must on the other hand have been virtually free from sand, just as the country is now south of the Kara-koschun, and that because by far the greater part of the drift-sand — probably the whole of it — which was blown across the lake, dropped into it, and so helped to fill up its basin. What happened when the Tarim shifted its position? This question is difficult to answer, because we do not know in what way the change in question took place. But whether it took place by successive steps, one after the other, or was effected all at once, as in the case of the Hwang-ho, the result was equally the same. In the former case the dunes would be washed away piecemeal, until the remnants that were left fell an easy prey to the storms. In the latter case the relatively narrow strip of desert which existed north-east of the new river-bed would be driven by the east-north-east wind directly against the left bank of the Kontsche-darja and the masses of sand which slipped down the lee sides of the outermost dunes would be swept away by the current into the river-bed, helping to fill up, not only the bed itself, but also any depressions and lakes there may possibly have been there. What the Kontsche-darja thus effected was to raise a barrier against the further westward advance of the mass of sand existing in that part of the desert. On the other hand as a consequence of the migration of the current from the Kuruk-darja to the Kontsche-darja (we are for the present disregarding the Tarim), the volume of the sand north-east of the lower Kontsche-darja or the Ilek increased rather than diminished in amount, because the old Lop-nor and the Kurukdarja no longer placed any hindrance in the way of the unrestricted movement of the drift-sand towards the west-south-west. The sandy desert begins indeed immediately above Turfan-karaul; above that point there is no drift-sand.
SW. NE.
/We,/ ... ~ /i~.
•
////iiiiiiuii.v.~i/ilia....,,.,,,.,.
i. .ii..,_.
Fig. 159.
One effect that the Kontsche-darja must inevitably have produced was to free from sand its right bank or, generally speaking, the country immediately south-west of the river, because the sand-dunes which previously existed there must have travelled farther towards the west-south-west, without any successors coming from the east to take their place. Hence the region that intervenes between the Kontschedarja or the Kuntschekisch-tarim and the Tarim itself must in course of time have become swept entirely clean of sand. And such exceptions to this as exist are to be explained by the fact that the vegetation which followed the water bound
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