Watch: Drone captures catastrophic avalanche on Nepal’s Mount Langtang

A Chinese photographer’s drone accidentally recorded the moment an enormous mixture of ice and rock tore down Nepal’s Mount Langtang Lirung. The footage gives researchers a rare view of the collapse behind a deadly chain of floods and landslides in the Himalayas.

Recorded from a mountaintop radar station in China on Aug. 26, the video shows a white mass cascading down the mountain before a huge brown dust cloud rises from the Lhende Khola Valley.

Researchers’ analysis suggests the disaster involved more than a glacier collapse. They believe the mountain’s rock face failed beneath a hanging glacier, sending a mass of rock and ice about 1,500 metres down the north face before it struck the glacier below.

The impact generated a magnitude 5.2 tremor and pushed debris and water into the river system. The resulting mudflow reportedly reached the Chinese customs and immigration building in Gyirong within about 20 minutes, then continued downstream toward the Trisuli valley.

Scientists are examining the footage to understand what triggered the collapse and to identify similar risks elsewhere in the Himalayas. They have pointed to the region’s fragile geology and warming temperatures, which can thaw permafrost that helps hold mountain rock together. Nepal continues rescue and rehabilitation operations after the wider disaster. The National Disaster Risk Reduction and Management Authority said the death toll had risen to 903, while about 4,247 people remained missing and 10,451 had been rescued.