The Yarlung Tsangpo Valley approximately the Tsangpo Gorge, where it is rather narrow together with underlain yesteryear alone most 250 meters of sediments. The mountains inwards the upper left corner belong to the Namche Barwa massif. Previously, scientists had suspected that the debris deposited yesteryear a glacier inwards the foreground was responsible for the formation of the steep Tsangpo Gorge — the novel discoveries falsify this hypothesis. Credit: Ping Wang
“I was extremely surprised when my colleagues, Jing Liu-Zeng together with Dirk Scherler, showed me the bear witness for this canyon inwards southern Tibet,” says Jean-Philippe Avouac, the Earle C. Anthony Professor of Geology at Caltech. “When I kickoff saw the data, I said, ‘Wow!’ It was amazing to run across that the river in ane trial cutting quite deeply into the Tibetan Plateau because it does non today. That was a large discovery, inwards my opinion.”
Geologists similar Avouac together with his colleagues, who are interested inwards tectonics—the study of the earth’s surface together with the agency it changes—can role tools such every bit GPS together with seismology to study crustal deformation that is taking house today. But if they are interested inwards studying changes that occurred millions of years ago, such tools are non useful because the action has already happened. In those cases, rivers decease a primary origin of information because they live on out behind geomorphic signatures that geologists tin interrogate to larn most the agency those rivers in ane trial interacted amongst the land—helping them to pivot downwards when the province changed together with yesteryear how much, for example.
“In tectonics, nosotros are ever trying to role rivers to tell something most uplift,” Avouac says. “In this case, nosotros used a paleocanyon that was carved yesteryear a river. It’s a squeamish illustration where yesteryear recovering the geometry of the bottom of the canyon, nosotros were able to tell how much the hit has moved upward together with when it started moving.”
The squad reports its findings inwards the electrical flow trial of Science.
Last year, civil engineers from the Communist People’s Republic of China Earthquake Administration collected cores yesteryear drilling into the valley flooring at v locations along the Yarlung Tsangpo River. Shortly after, one-time Caltech graduate pupil Jing Liu-Zeng, who at nowadays industrial plant for that administration, returned to Caltech every bit a visiting associate together with shared the essence information amongst Avouac together with Dirk Scherler, thus a postdoc inwards Avouac’s group. Scherler had previously worked inwards the far western Himalayas, where the Indus River has cutting deeply into the Tibetan Plateau, together with straight off recognized that the novel information suggested the presence of a paleocanyon.
Liu-Zeng together with Scherler analyzed the essence information together with establish that at several locations at that spot were sedimentary conglomerates, rounded gravel together with larger rocks cemented together, that are associated amongst flowing rivers, until a depth of 800 meters or so, at which dot the tape clearly indicated bedrock. This suggested that the river in ane trial carved deeply into the plateau.