Tsunami of dirt: what caused Nepal’s deadly glacial flood?

More than 150 people lost their lives and hundreds more are still missing after a massive surge of water, ice, mud, and debris swept down the Bhote Koshi River valley in Nepal. The valley serves as a crucial link between Kathmandu and Lhasa. Little warning was given before the flash flood, which left a shocking trail of destruction.

Experts believe an abrupt collapse of a glacier likely initiated the disaster, though they are still investigating the exact cause. Climate change is intensifying, causing glaciers worldwide to melt and contribute to disasters like these, especially in vulnerable regions like the Himalayas. There, permafrost – permanently frozen ground – is becoming destabilized due to rising temperatures.

If an earthquake or slope failure occurs, it can trigger a sudden and devastating debris flow. Early estimates suggest the wave may have reached heights of 30 meters. The landslide was initially mistaken for an earthquake with a magnitude of 4.4 on seismographs. At the China-Nepal border crossing of Gyirong Port, the debris wall resembled a tsunami of dirt.

While an earlier glacial lake outburst flood occurred in Nepal in 2024, early analysis indicates that was not the cause of this disaster.