Nepal flash floods were caused by glacial collapse, not earthquake: USGS

USGS now says a glacial collapse and debris flow triggered the Nepal flash floods. The revision rules out an earthquake and sharpens focus on climate-linked mountain hazards.Image used for representational purposes onlyThe flash floods that hit parts of Nepal were triggered by a glacial collapse and not by a 4.4 magnitude earthquake as reported earlier, the US Geological Survey (USGS) has said after further analysis.The floods, which originated in Tibet on Wednesday, left widespread damage in Nepal’s Rasuwa and Dhading districts. They killed 162 people and left 750 missing, including 133 Indian nationals.In an update to its note on the event, the USGS said, "This event was initially reported as a magnitude 4.4 earthquake. Additional analysis of nearby seismic stations, long period seismic waves, and satellite imagery led to the determination that the seismic event was instead a glacial collapse and debris flow, and that no earthquake had occurred." It also upgraded the magnitude of the seismic event to 5.2 from the 4.4 assessed earlier. "The USGS determined that the seismic event was a glacial collapse and debris flow that caused subsequent catastrophic impacts downstream," it said.Daniel Shugar, an Associate Professor of geomorphology at the University of Calgary in Canada, said the flash floods were triggered by a glacier that rolled off a cliff at 5,200 metres. He compared satellite images of the region taken on Wednesday and Tuesday, a day before the disaster struck Nepal. "Comparing satellite imagery from yesterday and today, the glaciers in the vicinity do seem to have lost a fair bit of snow in the last 24 hours," Shugar was quoted as saying by New Scientist magazine. "My guess is that snow melt, and glacier ice melt as well, injected a lot of liquid water into the glacier, which percolated down to the bed and lubricated it. That was enough for it to collapse," he said. The latest assessment from the USGS and satellite analysis indicate that the disaster was caused by a glacial collapse and debris flow, not an earthquake, with the floods going on to cause heavy loss of life and destruction in Nepal.With PTI Inputs - EndsPublished By: India Today Web Desk Published On: Aug 27, 2026 10:20 IST