Experiments on deaerating granular flows and implications for pyroclastic flow mobility

Granular flows were generated by the release of beds of particles in various fluidized states, which then deaerated in a horizontal channel. We describe characteristics of the flows and their deposits. Morphological similarities between deposits in experiments and in the field suggest that pyroclastic flow deposits form from a fluidized mixture. The experiments show that slightly expanded, fluidized flows are more mobile than non‐fluidized flows of equivalent volume and material composition. They travel to a fixed distance from their source, which depends only weakly on their initial degree of fluidization. Flows of fine particles (<100 μm) deaerate slowly and are highly mobile. Pyroclastic flows commonly have large amounts of fine ash, which may have a controlling influence on their high mobility.