Fig. 5: The fragmentation-induced fluidisation of pyroclastic density currents.

Conceptual summary sketch describing the process by which the evolution of the grain-size distribution transported induces compressibility effects in the granular avalanche, which in turn yields partially fluidisation and subsequently lowers the effective friction. The profiles shown are qualitative and not to scale. The grain size distributions are shown in the figure as inserts (A–E) whose locations are depicted in the main schematic drawing with the same labels (A–E).