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On October 13, 2000, the Expedition 3 crew of the International Space Station, high over Tibet, took this interesting photo of the Brahmaputra River. This mighty Asian river carves a narrow west-east valley between the Tibetan Plateau to the north and the Himalaya Mountains to the south, as it rushes eastward for more than 1500 km in southwestern China. This 15-km stretch is situated about 35 km south of the ancient Tibetan capital of Lhasa where the river flow becomes intricately braided as it works and reworks its way through extensive deposits of erosional material. This pattern is indicative of a combination heavy sediment discharge from tributaries and reduction of the river's flow from either a change in gradient or perhaps even climate conditions over the watershed.
The light color of the deposits and the milky color of the water is attributed to presence of glacial "flour," the fine material created by erosion from glaciers. Besides erosion by water and ice, this scene also depicts features created by wind. Note the delicate field of dunes on the alluvial fan toward the right edge of the image. The riverbed here is at an elevation of over 3,500 m, and with the long west-east extent of this barren valley, strong, persistent westerly winds also move and shape these deposits. Photos such as this one bring immediate visual understanding and appreciation of natural processes in some of the most remote locations on Earth. | |
