Mountain Collapsed, Not Just Glacier, Scientists Say After Nepal-Tibet Floods

Rescue teams searched Thursday for people still missing after catastrophic flooding along the Nepal-China border killed hundreds on Wednesday. Earth scientists are now reviewing satellite images to understand what caused the disaster. Initial pictures from Wednesday were hidden by clouds and dust. But clearer images from Thursday revealed a shocking finding. Geomorphologists Kristen Cook and Dan Shugar said the bedrock underneath a glacier had collapsed. This took a massive chunk of ice down with it, sending boulders and ice into the valley below. “You have this big bedrock failure that took part of the glacier with it,” said Shugar, an associate professor at the University of Calgary. The collapse happened near the Langtang Lirung peak, close to the Tibet border. After hitting the valley floor, the debris kept moving through the steep, narrow valley. Ice melted, and water and mud several stories high swept through communities. Shugar said it is heart-wrenching to look downstream from the collapse on the images. The debris has buried villages where people were living. Satellite images show the Trishuli River is now much wider. It is brown and black because it overtopped its banks and filled with debris. The color change shows how much mud and sediment the flow carried. Towns and villages along the river banks are submerged. Some houses are still poking through the brown debris. The flooding toppled buildings in Syapru Besi, a popular tourist spot where a famous trek to Langtang begins. A side river is now wider too, because the flow was so powerful it pushed upstream. Alton Byers, a mountain geographer at the University of Colorado at Boulder, called the flooding a “wasteland” that will take years to recover from. He has studied glacial hazards in Nepal for years and said this is the largest glacier flood he has seen, by far. Byers believes Wednesday’s flooding is related to climate change. He said warming is melting glaciers and permafrost, causing instability at high altitudes. This can trigger a series of cascading events. “All the indicators, to me, point to the impacts of warming trends,” he said. “The permafrost that for millennia has helped to hold together high-altitude rock and ice and soil and glaciers is now weakening and becoming unstable.” Cook and Shugar said they cannot yet say for sure there is a direct link to climate change. Slopes fail and landslides happen, Cook said, though permafrost is melting and destabilizing mountainsides. “While we cannot at this point directly link this collapse to climate change, it is not unexpected to see more events of this type with a warming climate,” Cook said. “Not this big, hopefully not this big.”