A deadly flash flood that swept through a remote region near Nepal’s border with Tibet was likely triggered when a large section of a glacier broke away and plunged hundreds of meters down into the valley below, experts say, citing satellite imagery from Planet Labs. While the exact cause of the glacier collapse remains unclear, Nepali officials pointed to a seismic tremor recorded in the area minutes before the disaster as a possible contributing factor.
Authorities on both sides of the Nepal-China border fear the final death toll will far exceed the nearly 100 fatalities confirmed so far. More than 300 trekkers remain missing, according to Nepal’s government.
Satellite images captured by Planet Labs — verified by Reuters — show a stark contrast: lush, green mountain slopes before the disaster now buried under rubble, boulders, and debris. ‘It is confirmed that a significant portion of the lower glacier front collapsed, triggering the event — likely carrying or incorporating substantial volumes of rock and sediment,’ said Vikram Gupta, a geotechnical expert and professor at Sikkim University in India.
Dan Shugar, associate professor of geoscience at the University of Calgary, noted that the imagery suggests a large volume of snow melted within the 24 hours preceding the flood. ‘Some glaciers in the valley were still snow-covered yesterday, but today they appear largely exposed ice. In other words — and without yet seeing data from any local weather station — unusually high temperatures were likely present,’ he explained.
The images compare the same valleys along the Nepal-China border on August 25, 2026 (before the floods) and August 26, 2026 (after the disaster), highlighting the scale of destruction. The Himalayan region urgently needs more robust early warning systems for such rapid-onset disasters, observers warn.
Nepal’s snow-capped mountains have lost nearly one-third of their glacial ice over the past 30 years due to global warming, according to a 2023 United Nations report. The agency added that glaciers in Nepal — situated between India and China, two of the world’s largest carbon emitters — melted 65% faster in the past decade compared to the previous one.
‘What I can see in the early-morning Planet Labs satellite images is that the lower section of the glacier detached at an elevation of approximately 5,200 meters and fell onto the valley floor, about 1,200 meters lower,’ said one analyst reviewing the imagery.