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Volcanology at the Tipping Point:  An Exploration of the Dynamics that Determine the Fate of Explosive Eruptions

Many processes in nature involve multiple, mechanically distinct phases: for instance, crystals settling in magmatic systems and ash particles interacting with a turbulent gas phase in an explosive volcanic eruptions. The interaction between these phases shape the landscape of all terrestrial planets, dictate interactions at the interface of the solid surface and the atmosphere and lead to the large scale differentiation of Earth and other planets. Examples of multiphase flows include explosive volcanic eruptions, Martian dust storms, sediment-choked rivers, crystal and bubble-laden magma chambers and marine turbidity currents. Although extremely common, the cumulative expression of numerous particle-particle and particle-fluid interactions can produce emergent meso-scale structure and self-organization that is difficult to predict.

I will discuss the use of multiphase models in addressing the different scales of fluid motion in volcanic multiphase flow as well as how they can provide a platform to integrate microphysical, analogue experiments and observational constraints. Microphysical experiments can provide the necessary closure for statistical mechanics based models, and provide a way to examine grainscale processes in a probabilistic manner. Such small-scale processes can dramatically alter the flow dynamics. In this talk I will discuss these critical events that help determine the fate of eruptive flows, with a particular emphasis on multiphase flow in volcanic conduits, plume entrainment, and granular segregation in pyroclastic density currents.