Glacier Collapse Raises New Fears for Nepal’s Mountain Communities

A devastating flash flood that tore through communities along Nepal’s Bhotekoshi River has renewed concerns that rising temperatures are making mountain regions more unstable. Satellite imagery indicates that a glacier collapse high in the Himalayas was likely the main trigger for the torrent of mud, water and ice that struck the border area on Wednesday. The disaster destroyed buildings and roads and left at least 360 people dead and 1,400 missing, according to the source report. A magnitude 4.4 earthquake was initially blamed for the collapse. Later analysis by the US Geological Survey suggested that the seismic energy instead came from a glacial collapse and debris flow. The failure involved a large section of ice crashing onto the northern slope of Langtang Lirung, a mountain about 7,000 metres high. The impact itself registered as magnitude 5.2. The resulting ice-and-rock avalanche forced boulders and debris into the Lhende Khola River, which feeds the Bhotekoshi. The International Centre for Integrated Mountain Development reported that water levels downstream rose by between seven and nine metres in roughly 30 minutes. Scientists are still studying the exact chain of events. However, the collapse occurred after a period of unusual heat. Ground temperatures measured by sensors around 10 kilometres away reached their highest level in two years two days before the event, according to glaciologist Hamish Pritchard. He said the heat may have weakened the snowpack, filled cracks with water and thawed the ice-and-rock bonds holding parts of the glacier in place. Monsoon conditions may also have played a role by saturating the soil and increasing river levels. Experts caution that this does not establish a single confirmed cause for the disaster, but they say global heating is weakening glaciers and permafrost in mountain regions worldwide. The Intergovernmental Panel on Climate Change warned in 2023 that warming would make formerly ice-bound landscapes increasingly unstable, increasing risks from floods and landslides. In Nepal’s Langtang catchment, glacier loss has increased more than fourfold since 1964, according to a study cited in the report. Researchers say similar vulnerabilities exist in the Alps, Caucasus, Andes, Himalayas and other high mountain regions. With retreating glaciers creating or enlarging meltwater lakes, one expert called for stronger disaster preparedness and urgent early-warning systems for communities in mountain valleys.