More than 1,200 people were killed and thousands remain missing after an Aug. 26 debris flow in northern Nepal raced downstream at over 160 kph, destroying villages toward India.
Satellite imagery indicates a 2.2-square-kilometer slab of bedrock and overlying ice detached from Langtang Lirung, releasing about 110 million cubic meters of material that turned into a fast-moving torrent.
Scientists say the collapse was likely primed by multiple factors: damage from Nepal’s 7.8-magnitude 2015 earthquake, roughly 2 C of regional warming since preindustrial times, and exceptionally high temperatures just before the failure.
Researchers also point to glacier retreat of more than 300 meters since 2010, thawing permafrost and meltwater-driven fracturing as mechanisms that weakened the mountain face and helped mobilize the debris.
The findings sharpen concern for other high mountain regions, with experts warning similar warming-driven rock-ice avalanches and glacial flood hazards could grow across the Himalaya, Andes and Alps without better mapping and early-warning systems.