High-mountain rock-ice avalanches pose increasing hazards in glacierized regions under climate warming, as illustrated by the 2025 Blatten disaster in the Swiss Alps (Büntgen et al., 2025). This study investigates how glacier entrainment affected the mobility of the 28 May 2025 Blatten rock-ice avalanche by integrating multi-source remote sensing, digital elevation model differencing, video interpretation, and three-dimensional material point method simulations. The model reproduces the observed runout footprint, with a simulated swept area of 2.85 square kilometres, an observed area of 2.69 square kilometres, and an intersection-over-union value of 0.82. The simulated motion evolved through five stages: rock destabilization, rock-ice interaction, channelized propagation, impact-induced diversion, and deposition. Glacier entrainment increased the moving volume from approximately 5.6 to 8.4 million cubic metres; however, its influence on mobility was stage-dependent rather than monotonically enhancing. During early rock-ice interaction, shear, compression, and interfacial friction dissipated rock kinetic energy and reduced motion efficiency. As the glacier body was progressively mobilized, ice velocity approached rock velocity and the entrained ice contributed momentum and gravitational potential energy to the coupled mass. Compared with a pure-rock scenario, total swept area increased from 2.16 to 2.85 square kilometres, whereas swept area per unit volume decreased from 0.386 to 0.339 square kilometres per million cubic metres. We therefore propose a stage-controlled entrainment model in which glacier ice shifts from an energy sink to an active moving component, complementing process-based rock-ice avalanche mechanics (Pudasaini & Krautblatter, 2014).
 

Ice-rock avalanche; Dynamic entrainment; Stage-dependent dynamics; Glacier entrainment; Material Point Method