An enormous chunk of glacier may have broken away and triggered the deadly flooding in Nepal and Tibet border on Wednesday, the New York Times reported, quoting a preliminary assessment by geologists and glaciologists.
Satellite imagery suggests a section of glacier about 2,000 feet wide broke off at an altitude of around 17,000 feet, falling nearly 4,000 feet to the valley below, said Daniel Shugar, a geologist at the University of Calgary in Canada.
“It looks like a glacier in the area basically snapped off in a clean break, allowing it to fall just over a vertical kilometer to the valley bottom,” Shugar said.
The event, known as an ice avalanche, sent ice and water cascading into the valley. Hundreds of people are missing in Nepal and the Chinese territory of Tibet after floodwaters swept through river valleys.
But scientists cautioned that it was too early to determine the precise cause of the flooding or rule out other contributing factors.
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A drone view shows mud covering properties following a flash flood at Trishuli in Nuwakot district, Nepal, August 26, 2026. REUTERS/Stringer
Simon Cook, a glaciologist at the University of Dundee in Scotland who analysed satellite imagery with Shugar, said the large mass of ice stored at high altitude would have had enormous potential energy as it fell.
“When it breaks off, he added, the sheer force of the drop pounds the ice into a dangerous, fast-moving mix,” according to the analysis.
“That ice just gets pulverized into water,” Cook said.
The glacier break occurred about 40 miles north of Kathmandu, according to the group's analysis. The resulting flow moved northwest through the valley towards the Bhotekoshi River, along the border between Nepal and the Chinese territory of Tibet.
Cook said the event was similar to a 2021 glacier collapse in India's Uttarakhand state that caused major flooding and killed more than 100 people.
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A drone view shows mud covering properties following a flash flood in Trishuli, Nuwakot district, Nepal, August 27, 2026. REUTERS/Navesh Chitrakar
Local seismic data showed that a large mass suddenly moved downhill at about 8:40am local time, followed immediately by a signal indicating flooding, said Kristen Cook, a geomorphologist at Université Grenoble Alpes in France.
“I see a signal that is quite large at the start of the event, but it does not look like an earthquake,” she said.
“When we combine this with what we know about the area and satellite imagery, we come to a preliminary interpretation that this was most likely a rock-ice avalanche that transitioned into a flow as it moved downstream.”
The US Geological Survey initially recorded a magnitude 4.4 earthquake in the area at around the same time. It later determined that the landslide itself had generated the seismic signal.
The USGS said the force of the landslide registered as magnitude 5.2.
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A drone view shows mud covering properties following a flash flood in Trishuli, Nuwakot district, Nepal, August 27, 2026. REUTERS/Navesh Chitrakar
Scientists said warming temperatures linked to climate change may have accelerated the glacier's collapse, although there is not yet enough evidence to establish a direct cause.
Shugar said satellite images showed snow cover had rapidly diminished in the previous day, suggesting warmer temperatures that may have contributed to the ice avalanche.
The Himalayas are warming rapidly, increasing concerns about the risks posed by melting glaciers and unstable mountain slopes.
However, cloudy conditions have limited the availability of up-to-date satellite imagery, and scientists said their understanding of what caused Wednesday's flooding should become clearer in the coming days.
Shugar also cautioned against ruling out other possible causes.
“The amount of water in the videos is astounding, an order of magnitude bigger than other recent glacial disasters like this,” he said. “It’s very possible that there’s another culprit here.”
