IIIF Color HighRes
National Institute of Informatics - Digital Silk Road Project
| |||||||||
|
| IIIF Color HighRes |
| Scientific Results of a Journey in Central Asia, 1899-1902 : vol.4 |
 |
 |
 |
 |
 |
 |
|
|
 |
|
|
|
|
|
|
|
|
Citation Information
{
HYPSOMETRY AND RELIEF OF THE TIBETAN PLATEAU.
593
Dutreuil de Rhins the Jäschil-köl lies at 5000 m., but according to Deasy at 4890 m. The altitude of the Horpa-tso is 5466 m. and 5186 m. according to Bower and Deasy respectively. As in these cases it is impossible to decide which is right, it seems best to take the two values; by so doing we shall at any rate get the mean between them.
The mean altitude for the thirty-seven western lakes is 4837 m. and for the fifty-eight eastern lakes 48i i m. Thus the difference between them is only slight, namely 26 m. If we pick out the five highest lakes in each group, !heir mean altitudes are 5227 m. and 5104 m. respectively, and the difference amounts to 123 m. By comparing Deasy's six highest lakes with my six highest, we get means of 5056 m. and 5001 m., with a difference of 55 m. The mean altitude of the twenty highest lakes in the west is 5044 m. and of the twenty highest in the east is 4983 m., and the difference 61 m. Thus no matter how you group the lakes, the mean altitude of those in the west is always a trifle higher than the mean altitude of those in the east. But this law does not hold good for the separate individual lakes, for it is perfectly self-evident that many of the eastern lakes lie higher than many of the western. Our comparison is restricted to the true plateau country; in the more peripherally situated lakes the relations are different. The Tengri-nor (4609 m.), for instance, lies 292 m. higher than the Panggong-tso (4317 m.), but Manasarovar (466o m.) lies 45o m. higher than the Jamdok-tso (4210 m.).
These mean lake-altitudes become of especial interest when we compare them with the mean values for the pass-altitude and the plateau base: —
| Western Tibet. | Eastern Tibet. | Difference. | |
| Pass-altitude | 5477 | 5189 | 288 |
| Base-altitude | 5109 | 4910 | 199 |
| Lake-altitude | 4837 | 4811 | 26 |
| Difference between pass and lake . | 640 | 378 | 262 |
| » » »» base | 368 | 279 | 89 |
| » » base » lake . | 272 | 99 | 173 |
These figures show very distinctly that the surface-moulding of western Tibet is considerably more accentuated in relief than the surface-moulding of eastern Tibet. The table shows, for instance, that the difference of altitude between the plateau and the lake levels amounts in the west to 272 in., whereas in the east it is only 99 m. The difference between the pass and lake levels is in western Tibet 262 m. greater than in eastern Tibet. The western passes are 288 m. higher than the eastern; in the west the plateau-base is 199 m. higher than in the east; but the western lakes lie only 26 m. higher than the eastern lakes. These figures tell us directly, that the western lakes lie in deeper valleys and are surrounded by relatively higher mountains than the eastern lakes, and that the latter occupy broad, flat valleys and are surrounded by relatively low mountains. In other words denudation has advanced farther in the east than it has in the west. In the east we have a country which has already reached a condition of stagnation and its self-contained drainage-basins are being progressively filled up. The same thing is no doubt true
h'edin, Tourney in Central Asia. IV 75
|
|
|
|
|
|
|
|
|
Copyright (C) 2003-2019 National Institute of Informatics and The Toyo Bunko. All Rights Reserved.