Unraveling Ice‐Driven Hypermobility in Debris‐Ice Avalanches Through Cryogenic Centrifuge Modeling

Debris‐ice avalanches (DIAs) in high‐altitude regions are characterized by hypermobility and catastrophic damage potential; however, the mechanisms governing their hypermobility remain poorly understood. A specialized centrifuge modeling system, which is equipped with particle image velocimetry and basal stress measurements and operates under a cryosphere environment (−5°C), was developed to investigate the flow dynamics and hypermobility of DIAs. Kinematically, increasing ice content amplified basal slip, surface velocity, and apparent shear rate. Crucially, we identified a critical quantitative divergence: while the intrinsic frictional weakening of ice lowers the static friction coefficient by 21%, the macroscopic effective friction coefficient drops by 58%. This discrepancy underscored that intrinsic material properties alone were insufficient to explain the extreme mobility of DIAs. Analysis of the dimensionless inertial number ( I ) indicates that ice‐rich mixtures evolve into a pronounced collisional‐frictional regime ( I = 0.16–0.26), suggesting a transition to a state dominated by intense particle‐level interactions. Finally, a plausible dynamic mechanism was proposed that ice‐driven basal agitation generates stress fluctuations that effectively suppress flow resistance. These findings suggest that the hypermobility of DIAs arises from a synergy of reduced intrinsic friction and basal agitation‐induced dynamic friction reduction, providing critical insights into geophysical flows in the cryosphere.