Snowslab avalanches start with the failure of a weak snow layer buried below a cohesive snow slab. After failure,the very porous character of the weak layer leads toits volumetric collapse and thus closing of crack facesdue to the weight of the overlaying slab. This complex process, generally referred to as anticrack, explains why avalanches can be remotely triggered from flat terrain. On the basis ofa new elastoplasticity model for porous cohesive materials and the Material Point Method, we simulatedthe dynamics of propagating anticracks reportedin snow fracture experiments as well as the propagation and reflection of localized compaction bands . Finally, we simulated the release and flow of slab avalanches at the slope scale triggered either artificially (bombing) oraccidentally (remote triggering).Our unifiedmodel represents a significant step forward as it allows simulating the entire avalancheprocess, fromfailure initiation to crack propagationandsolid-fluid phase transitionsin snow, which is of paramount importance to mitigate andforecast snow avalanches as well as gravitational hazards in general.