Himalayas face growing rock-ice avalanche risk as temperatures rise: Experts

Time of India

22-06-2025

Dehradun: The recent rock-ice collapse on Switzerland's Birch Glacier, which buried 90% of the alpine village of Blatten under nine million cubic metres of ice, rock and debris, has reignited global concern over glacial instability amid rising temperatures.
While a timely evacuation prevented casualties, the incident highlighted the growing threat of rock-ice avalanches (RIAs) – sudden, massive slope failures triggered by thawing permafrost and heavy debris accumulation.
A recent study published in a peer-reviewed scientific journal 'Landslides' (Springer) has raised alarm about the increasing frequency and intensity of such events across High Mountain Asia (HMA), which includes the Himalayas, Karakoram and Tibetan Plateau.
An analysis of 60 large-scale RIAs revealed that these disasters claimed at least 1,366 lives and inflicted extensive damage to ecosystems, water resources, infrastructure and local communities.
Notable examples include the 2015 Langtang avalanche in Nepal, which killed roughly 350 people, and the 2021 Reni disaster in Chamoli, Uttarakhand, which left over 200 dead and destroyed two hydropower projects.
A rock-ice avalanche is the rapid downslope flow of a mixture of rock and ice, often initiated by the collapse of a rock mass on or near a glacier.
These events are particularly hazardous in glaciated mountain regions due to their high speeds, long runouts, and potential to evolve into devastating debris flows.
The study found that 86% of these avalanches originated from steep, high-altitude slopes — mostly north or northeast-facing — and were primarily triggered by a combination of permafrost thaw, seismic activity and unstable bedrock. Nearly half of the events triggered cascading disasters, increasing their destructive potential tenfold and allowing runouts of up to 30 km.
Experts warn that similar conditions are emerging across the Himalayas, where accelerating glacier thinning, warming permafrost, intense monsoonal rains and tectonic activity are converging to create a high-risk environment.
"Global warming and temperature variability are altering glacial mass balance and thawing permafrost, heightening the risk of extreme events like rock-ice avalanches," said Dr Farooq Azam, a cryosphere expert at the International Centre for Integrated Mountain Development (ICIMOD) in Nepal.
Geologist and former executive director of the Uttarakhand State Disaster Management Authority, Piyoosh Rautela, explained that cascading events are more likely when avalanches start from small, steep glaciers and feed into high-discharge river systems. "Medium-sized avalanches are particularly dangerous due to their ideal mix of debris volume and mobility," he said.
Pierre Yves, senior advisor on Disaster Risk Reduction and Climate Change Adaptation at the Swiss Agency for Development and Cooperation, warned that continued warming, especially in permafrost zones, makes high-altitude Himalayan slopes increasingly prone to collapse. "Urgent hazard mapping and early warning systems are essential, especially in valleys with habitations and critical infrastructure," he said.