Collaborative Research: How Topography Shapes Pyroclastic Density Current Hazards

Pyroclastic flows – hot, fast currents of gas and volcanic rock – have caused one third of all deaths in volcanic eruptions. Scientists need to communicate the risks of these flows to the public by making hazard maps and through public information about the dangers. Despite this need, there is a poor understanding of how hills and valleys impact the travel of pyroclastic flows. This project will use products and photographs of the eruption of Mount St. Helens on May 18, 1980, to document how the flow reacted when it encountered hills and valleys. Computer models will be run to see how the speed and other properties of the current change with time. In addition to increasing understanding of pyroclastic flows, the results will be used to build an exhibit of the eruption to share with schools and museums to help educate the public about volcanic hazards. Scientists cannot see inside deadly pyroclastic flows and so they must use numerical models to study their internal dynamics. Most such models usually treat pyroclastic flows as homogeneous and dilute and do not account for how the flows will evolve in space and time when they encounter rough topography. This project seeks to improve the understanding of how topography impacts pyroclastic flows by creating a 4D model of the flow from mapping orientations of trees knocked over by the current as it traveled across rugged topography. The model will also incorporate information in a series of closely timed pictures of the Mount St. Helens eruption taken from different locations around the volcano. The 4D model will provide the foundation to compare computational models to test how changes in flow velocity, density, and temperature controlled the response of the flow to real-world topography. A mobile display for schools and museums will incorporate the 4D model and recorded eyewitness accounts to help educate the general public about the hazards and risks of pyroclastic flows. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.