Large-scale experiments on volcanic processes

Some of the least understood and most hazardous geologic processes involve complex multiphase flows, particularly those related to explosive volcanic eruptions. These phenomena inherently involve a wide range of characteristic length and time scales, as well as processes that are coupled across those scales in a range of flow regimes. For example, a pyroclastic density current's (pyroclastic flows and surges) behavior is governed in a complex way by the interactions between individual particles (∼10^-4 to 10 ¹ meters, ∼10^-1 to 10¹ seconds) and by turbulent mixing with surrounding air (∼10^-2 to 10² meters, 1 to 10² seconds). Material properties within individual flows can vary over huge ranges; for example, when ascending magma interacts with groundwater in a volcanic conduit, the viscous melt and liquid water are transformed into brittle glass and steam.