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.3 | |
| 1899-1902年の中央アジア旅行における科学的成果 : vol.3 |
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引用情報
| TIBETAN QUAGMIRES - THE GLACIAL MOUNTAIN. | 87 | ||||
| are evidently formed out of older deposits of disintegrated matter which is modelled by the advancing erosion. In the spaces between the distinctly marked erosion channels the water flows in very thin broad sheets amongst the detritus, and thus gradually washes away the finer material, leaving the schists on the top, and this superficial layer of schists has no hard rock underneath to support it. If now this detritus material were only dry, it would of course bear, but it is softened incessantly by rain and melting snow, which does not make its escape in the form of determinate brooks, but for the most part penetrates vertically into the ground where it falls. The entire absence of vegetation is another important factor: there is not a single blade of grass within sight, not a single root imparts firmness to the ground: it is all in a state of flux, loose and disconnected. In the sequel we shall find that ground of this type is characteristic of the Tibetan highlands, especially where they are flattest and the erosive energy is least. This boggy, unstable condition of the surface constitutes one of the principal difficulties that a caravan has to contend against in those regions. Some parts of the plateau cannot possibly be explored except in winter. At the point where we turned the altitude was 5,248 m. On the south-western side of the ridge up which we attempted to ascend there was a shallow rainwater channel, into which such water as does not sink into the ground gradually gathers. The bed of this muddy yellow brook, which swelled eventually to the volume of a couple of cubic meters, was fairly firm, and as we had no other choice, we perforce marched in the water. This led us north-west and west-north-west towards the next self-contained drainage-basin. The ridges on both sides gradually grew relatively lower and flatter, and the country began to open out. On the north we had quite close at hand two small patches of sand with low dunes, which turned their steep face towards the east. Seeing now that dunes demand an arid climate as the condition of their formation, it is indeed strange to find them existing in such a moist region as this. They prove at all events that periods of dryness do occur here at some time or other of the year. Farther to the north rose the range which we had lately crossed over; towards the west it appeared to grow lower. One of the most conspicuous peaks of the great glaciated mass, E, was everywhere visible. To the south an entire series of stupendous peaks stood out in strongly accentuated whites and blues. The brook gradually gathered strength, and finally ran into two miniature lakes (alt. 5,084 m.), or rather into a large pool with a narrow »waist» in the middle. The upper basin was of a dirty green colour, the lower yellow. One would have expected the opposite, for the brook itself is a muddy yellow. Probably the upper basin is the deeper. The brook flows through them both, for it issues from the lower pool and continues its western course, with a slight inclination towards the south. As it advanced its basin grew increasingly deeper. The reddish yellow ground on both sides of the brook consisted of soft mire; in one place it formed a small pool of about a score of meters in diameter. Next, from the south-east, there came another brook, considerably larger, and divided into several arms in a broad bed. After the two brooks have united, and have picked up a third brook coming from the north, the channel grows deep and narrow, and the schists crop out on both sides in its inclosing terraces. The volume would be | |||||
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