Particle Trajectories in Volcanic Plumes: Model Development and Testing at Inyo Craters, California, United States

The main goal of this research is the development of a model for volcanic plumes that tracks the paths of rocky particles (pyroclasts or tephra) within the plume and calculates where these particles fall. One impact of the proposed research for society is to use the model to forecast the proximal (near to the vent) portion of potential tephra fall maps, which are an important part of hazards forecasting and hazards potential mapping at volcanoes worldwide. It is also planned to use the model to generate new graphical calculation plots to estimate eruption parameters, such as eruption column height and windspeed, from tephra fall data. The field portion of the research at Inyo Craters, CA, will provide important constraints on potential future eruptions that could impact major transportation corridors and watersheds in the rapidly growing corridor between Reno and Los Angeles?Las Vegas. Additional broader impacts include the integration of underrepresented groups and scientific disciplines through the training of a female Ph.D. student in both Geology and Computational Sciences. The investigators have broken the problem into several parts. The first part, which will be addressed by this research, is to model the proximal fallout of large pyroclasts by simulating the motion of large particles in eruptive flow fields. A large-particle module (LPM) is being written to work with and potentially be added to ATHAM (Active Tracer High resolution Atmospheric Model), a dynamic volcanic plume simulation. The module will be used to investigate pyroclast paths and distributions within the plume as constrained by still and video photography, and to test model predictions against field data on pyroclast distribution on the ground. For the field portion of the research, it is proposed to map and measure deposit thickness and grainsize in the proximal region of carefully chosen eruption deposits using differential GPS for precise location. They will study the most recent, large Plinian-type eruption deposits in the southwestern U.S., the Inyo tephras. The field data will be analyzed by statistical comparison of the modeled and the measured distributions of clasts on the ground. The goodness of the model will be characterized by using the degree of its convergence to the field data, and comparing this degree of convergence to the results from using past models. It is envisaged that the proposed research will result in the development of a large particle module that works with and can be incorporated into ATHAM to begin to produce the first full, 3-D tephra deposition simulation. Given appropriate eruptive conditions, the simulation should produce visualizations of pyroclast position and concentration within the plume, as well as distributions of large pyroclasts on the ground, and thickness, isomass or grain size isopleths in good agreement with field data.