Nepal glacial collapse kills 1,300, leaves 5,600 missing

A glacial mountain collapse on Nepal’s border with China has killed more than 1,300 people and left more than 5,600 missing in the two countries, as scientists examine what caused the August 26 disaster.

Experts say a mass of ice and rock broke away from the north face of Nepal’s Langtang Lirung mountain at 8:37 am local time, sending debris down the valley. The Kathmandu-based International Centre for Integrated Mountain Development said the collapse began at an altitude of about 5,200 metres, with a section more than a kilometre wide and about 700 metres high.

The debris fell about 800 metres onto a debris-covered glacier, then surged downhill and briefly dammed the Lhende River before water and debris burst downstream. ICIMOD geologist Sudan Bikash Maharjan said the debris travelled about 20 kilometres and dropped 1,700 metres at Rasuwagadhi in about seven minutes.

Experts say several factors may have contributed, but it is too early to identify a single trigger. They said there was no earthquake, exceptional rainfall or sudden period of extreme heat immediately before the collapse.

The glacier in the area retreated by about 450 metres between 1990 and 2020, exposing rock that had previously been covered by ice. Experts say temperature, moisture and permafrost changes may have weakened fractures in the exposed rock, while water entering cracks could have helped destabilise the slope.

Geoscientist Jakob Steiner said climate change makes such events more likely, but cautioned that mountain collapses are also part of natural geological processes.

Scientists are reviewing possible warning signs, including evidence that the glacier accelerated in the weeks before the collapse and a sudden increase in meltwater shortly beforehand. Steiner said that did not mean authorities in Nepal or China would have known the mountain was about to fail.

Experts say better long-term monitoring, data sharing and coordination could help identify future risks.