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Larry G. Mastin, Ph.D.

I have spent much of my career working to understand, assess, and mitigate the hazards of volcanic ash. 

 To understand the nature of the hazard, I have studied tephra deposits in the field and designed experiments to generate volcanic ash in the laboratory.  I also develop and use models that simulate the ascent of magma in conduits, rise of ash in volcanic plumes, and downwind movement of ash clouds.  I have been involved in the development and application of several models that simulate these processes.

I have worked with emergency managers, Volcanic Ash Advisory Centers, and specialists from more than a dozen volcano observatories around the world to improve the accuracy of volcanic ash forecasts, both for aviation safety and for ground-based communities.  From 2010-2020 I served as co-chair of the World Meteorological Organization’s Volcanic Ash Scientific Advisory Group, an expert panel dedicated to advising Volcanic Ash Advisory Centers on the science and practice of volcanic ash-cloud detection and forecasting.

My professional life began as a mud logger working on the North Slope of Alaska in 1980-81.  While studying for my master’s degree at Stanford in 1982-84, I worked part time for the Tectonophysics branch of the USGS in Menlo Park, California, where I assisted with hydraulic fracturing stress measurements, and studied the growth of fractures and the development of breakouts, i.e. stress-induced zones of failure, around boreholes in sandstone.

My Ph.D. work at Stanford, from 1984-1988, under Professor David Pollard, involved field and laboratory study of the growth of surface faults above a shallow dike in Long Valley Caldera, California.   A second half of this study focused on how the dike heated groundwater that erupted to produce several large explosion craters, the Inyo Craters, north of the town of Mammoth Lakes.

After completing my Ph.D., I worked from 1988-1990 as a post-doctoral researcher in the Geophysics Institute at the University of Karlsruhe, Germany.  My tasks included compiling data for the European part of a World Stress Map project, and examining the state of stress at a deep drillhole site in northern Bavaria.

At the Cascades Volcano Observatory, from 1990 through the late 2000s, I concentrated on the role of water in the style and timing of eruptions.  This work involved, for example, an examination of correlations between rainfall and gas explosions at Mount St. Helens; on the conditions that produced explosive phreatomagmatic eruptions at Kilauea, and effects of turbulent water-magma mixing on eruptive style.

Since the late 2000s, I have been involved primarily in volcanic ash hazards, as described above.

*Disclaimer: Listing outside positions with professional scientific organizations on this Staff Profile are for informational purposes only and do not constitute an endorsement of those professional scientific organizations or their activities by the USGS, Department of the Interior, or U.S. Government