An earthquake-triggered avalanche in Nepal in 2015 was exacerbated by climate variability and snowfall anomalies

On 25 April 2015, the Gorkha earthquake triggered a large rock-ice avalanche and an air blast disaster in the Langtang Valley, Nepal. More than 350 people were killed or left missing. Here we reconstruct the evolution of the Langtang avalanche-air blast using field investigations and numerical modeling and examine the influence of two primary climate-related phenomena: snowfall anomalies and warm temperatures. Our findings suggest a deep snow cover fosters the formation of a dispersed avalanche, which increases the mobility and destructive power of the powder cloud air blast. Elevated air temperatures intensify meltwater production and lubricate the flowing mass. Both mechanisms contributed to the Langtang disaster. Our study underscores the essential impact of snow cover and air temperature on the risk assessment of high-altitude rock-ice avalanches, highlighting how seasonal and climatic variations affect avalanche runout and air blast dynamics.