Collaborative Proposal: Experimental Studies of Dilute Pyroclastic Density Currents

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Pyroclastic density currents are hot and fast-moving mixtures of solid particles and gas produced by explosive volcanic eruptions or the collapse of lava domes. They travel great distances, pose substantial hazards, and alter landscapes. The processes governing the movement of, and transport in, pyroclastic density currents are not well understood quantitatively. Even conceptual models remain controversial. Basic questions remain about how hills, ridges, and valleys alter and direct pyroclastic density currents and about how air mixes into the currents. These key processes control current speed, direction, and injection of ash into the atmosphere. The long term outcome of better understanding pyroclastic density currents is a scientific foundation for assessing the hazards they pose.This project will use dynamically scaled laboratory experiments, in particular their interaction with topography, to understand pyroclastic density current dynamics. This will be accomplished by imaging the three-dimensional velocity and concentration fields inside modeled dilute pyroclastic density currents, and quantifying the entrainment of air and sedimentation of particles. This understanding will improve our ability to relate field deposits to the dynamics of these currents. The experimental setup is designed to permit a large number of experiments and hence to explore relationships between parameters and processes.