Very-high-resolution optical imagery reveals key clues to the Langtang Lirung ice–rock avalanche

Tommaso Carlà , Veronica Tofani, Nicola Casagli

Ice–rock avalanches and resulting cascading processes are increasingly recognized to pose an exceptional risk to high-mountain systems. Once initiated, they often transition from dense multiphase mixtures to water-saturated debris flows and even hyper-concentrated floods, thus attaining sufficient runout potential to move from highly remote to populated regions. The event that originated from the northern flank of the Langtang Lirung on 26 August 2026 is the most recent and dramatic example. Here we document an archive of 11 very-high-resolution (VHR) optical images of the avalanche source area, highlighting the overall stationarity of the glacier tongue in the 6 years preceding its collapse. In contrast, remarkable indicators of a deep-seated failure mechanism are observed in the outcropping bedrock, pointing to intrinsic rock mass structural weakness and long-term preconditioning as opposed to sudden climate-related triggering.