A massive landslide triggered by the collapse of a glacier and rock on the north face of Langtang Lirung in Nepal on August 26 released over seven billion cubic feet of debris, equivalent in volume to roughly 100 football stadiums. The disaster, which caused flash flooding, has resulted in more than 1,000 confirmed deaths, with thousands still missing. The event left a large scar on the mountainside near Nepal’s border with Tibet and is now the focus of scientific investigation to determine the precise causes.
Experts studying the incident suggest that the collapse likely began as a rock failure that broke down the glacier above it. Satellite data analyzed by researchers revealed that a rock outcrop at the glacier’s edge had shifted more than a foot in the month preceding the event, with movement accelerating during that time. The glacier’s retreat over the last century exposed unstable rock faces previously supported by ice, contributing to their vulnerability.
Kristen Cook, a geomorphologist at Université Grenoble Alpes in France, explained that bedrock failures are difficult to predict due to the steep and extensive slopes throughout the Himalayas. She noted that the collapse was probably the result of multiple factors accumulating over time. Meltwater from the glacier may have seeped into cracks in the bedrock, which expanded as the water froze and thawed repeatedly. Additionally, the retreating glacier exposed rock faces and thawed permafrost within them, allowing further water infiltration and weakening the rock’s structure.
W.W. Immerzeel, a mountain hydrologist at Utrecht University, observed that the nearly straight cut formed on the mountainside after the landslide suggests the failure originated in the bedrock beneath the glacier. The immense drop—nearly one mile from the mountain face to the valley floor—amplified the energy of the collapse, pulverizing and partially melting the ice to create a fast-moving slurry of ice, rock, and sediment.
The resulting debris flow traveled over 60 miles downstream with an estimated peak speed exceeding 100 miles per hour. It caused widespread destruction, obliterating towns and bridges along its path. The force of the collapse also registered as a magnitude 5.2 earthquake.
Scientists warn that such landslides may become more frequent as climate change accelerates glacier retreat and permafrost thawing in mountain regions worldwide. Cook highlighted concerns for the Alps and other high mountain areas that are experiencing rapid warming. The tragedy in Nepal underscores the increasing risks posed by environmental changes in vulnerable mountainous landscapes.