New research suggests that the plateau edge might have been preserved for thousands of years by ice during glacial advances and by glacial debris deposited at the mouth of many Tsangpo tributaries during warmer times when glaciers retreated. Those debris walls, or moraines, acted as dams that prevented the rapidly traveling water in the main Tsangpo gorge from carving upstream into the plateau.
"At the edge of the plateau, the river's erosion has been defeated because the dams have flattened the river's slope and reduced its ability to cut into the surrounding terrain, making it more like a lake," said David Montgomery, a University of Washington geomorphologist.
Montgomery is co-author of a paper in the Oct. 9 issue of Nature that describes a new hypothesis of why the Tibetan Plateau has maintained its elevation when it appears it should have been worn down in the area of the Tsangpo system.
The paper's lead author is Oliver Korup of the Swiss Federal Institute for Snow and Avalanche Research in Davos, Switzerland. The work was financed in part by the European Commission and the National Science Foundation in the U.S.
The researchers focused on the three primary rivers of the Tsangpo system, the Yarlung Tsangpo and its two major tributaries, the Yigong Tsangpo and the Parlung Tsangpo. The scientists mapped geologic evidence of more than 300 natural dams, including 260 moraines, that have formed repeatedly at the mouths of tributaries in the last 10,000 years to block water flow on the three main streams.
The first evidence of the dams was found at the edge of the Tibetan Plateau, and additional evidence continued to be found upstream, Montgomery said. The dams essentially formed giant lakes along the river and prevented the water from carving into bedrock.
"The glaciers seem to have helped preserve the edge of the plateau by keeping the river from ripping into it," he said. "This isn't the explanation for why the rest of the plateau is so well preserved, but it might work for this area where the Tsangpo crosses the edge of the plateau."
There are two well-recognized mechanisms that typically are thought to be responsible for preserving a feature such as the edge of the Tibetan Plateau. But one of them, the plateau's arid climate, is not to blame because the Tsangpo is already a large river at the point that it enters the world's deepest and fastest-eroding gorge. The other conventional explanation, that tectonic faults continually push new rock to the surface and thus offset any erosion by the river, might be at work in concert with the glacial damming, the scientists believe.
In the Tsangpo gorge, also called Yarlung Tsangpo Grand Canyon, the river plunges from about 10,000 feet to about 1,000 feet in a span of 150 miles. Eventually the river becomes the Brahmaputra River, flowing through India and Bangladesh and into the Bay of Bengal.
"Up in the gorge, the river is very steep and the erosion is very high, and one would think that back through geologic time it should have sliced upstream into the Tibetan Plateau," Montgomery said.
The question is why that didn't happen. Korup and Montgomery suspect that the glacial dams on tributaries right to the edge of the plateau prevented such pronounced erosion.
"It's a transition from where the river is doing all the erosion at lower elevations to where the glaciers are doing all the erosion at high elevations, and the glaciers are limited on how deeply they erode," Montgomery said. "They shave off the top but they don't erode farther down, and the rivers can't erode back past the glaciers."
Vince Stricherz | EurekAlert!
Research sheds new light on forces that threaten sensitive coastlines
24.04.2017 | Indiana University
NASA sees the end of ex-Tropical Cyclone 02W
21.04.2017 | NASA/Goddard Space Flight Center
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
24.04.2017 | Life Sciences
24.04.2017 | Earth Sciences
24.04.2017 | Machine Engineering