A group of scientists from Caltech and China Earthquake Administration said they have discovered a deep ancient canyon buried under Yarlung River (also known as Yarlung Tsangpo) in the south of Tibetan Autonomous Region.
The study shows about 2.5 million years ago, Yarlung Tsangpo had created a deep canyon at least 500 meters below its current riverbed. “The data tells us that the river had incised deeply into the margin of Tibetan Plateau and then at a later stage the tectonic uplift created the gorge and made this river so steep,” Dirk Scherler, a geologist and one of two lead authors of the study, told VOA's Tibetan Service.
The study, which was published in American Association for the Advancement of Science a week ago, shows that as collision of Indian Plate and the Eurasian Plate lifted the Tibetan Plateau, sediments from the tectonic activities filled up the ancient canyon. Through drilling, the scientists determined that the ancient canyon was, in some part, 1000 meters deep.
“I was extremely surprised when my colleagues, Jing Liu-Zheng and Dirk Scheler, showed me the evidence,” said Jean-Philippe Avouac, the Earle C. Anthony Professor of Geology at Caltech. “That was a big discovery, in my opinion.”
According to Scheler, who now works at GFZ German Research Center for Geosciences, the buried-canyon extends for about 300 kilometers upstream from the Yarlung Tsangpo Grand Canyon, a well-known gorge that some regards to be deeper than the Grand Canyon in U.S. and slightly longer.
Tibet, once located under ocean, is a young plateau with lively seismic activities. The tectonic forces in the Earth’s crust continues to build mountains, glaciers make valleys and rivers make canyons. As the Himalayas continue to grow, Indian monsoons continue to feed the Tibetan rivers, which incise the plateau.