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.
Education and Certifications
1988 Ph.D. Geomechanics, Stanford University
1984 M.S. Engineering Geology, Stanford University
1980 B.S. Geology, University of California, Davis (cum Laude)
Affiliations and Memberships*
Fellow, Geological Society of America
Member, American Geophysical Union
Member, International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI)
Member, American Meteorological Society
Member, American Association
Honors and Awards
2018: Fellow, Geological Society of America
Abstracts and Presentations
2021: “Comparing the hazards of wildfire smoke and volcanic ash in the Pacific Northwest”, invited talk in the Cascadia Wildfire and Urban Smoke seminar series, sponsored by Portland State University and the Cascadia Innovation Corridor Iniative (search for it on YouTube)
2020: “Protecting air travel from volcanic ash in the coming decade”, invited talk V08-15 at 2020 American Geophysical Union Fall Meeting.
2016: “Forecasting Ashfall Impacts from a Yellowstone Supereruption”, USGS Menlo Park Public Lecture, May 26, 2016, https://www.usgs.gov/media/videos/forecasting-ashfall-impacts-a-yellowstone-supereruption
Science and Products
Results of the eruptive column model inter-comparison study
Volcanic lightning and plume behavior reveal evolving hazards during the April 2015 eruption of Calbuco volcano, Chile
Adjusting particle-size distributions to account for aggregation in tephra-deposit model forecasts
Hail formation triggers rapid ash aggregation in volcanic plumes
Evidence for large compositional ranges in coeval melts erupted from Kīlauea's summit reservoir
Electron microprobe analyses of glasses from Kīlauea tephra units, Kīlauea Volcano, Hawaii
Cycles of explosive and effusive eruptions at Kīlauea Volcano, Hawai‘i
Testing the accuracy of a 1-D volcanic plume model in estimating mass eruption rate
Modeling ash fall distribution from a Yellowstone supereruption
User’s guide and reference to Ash3d—A three-dimensional model for Eulerian atmospheric tephra transport and deposition
Injection, transport, and deposition of tephra during event 5 at Redoubt Volcano, 23 March, 2009
A Bayesian method to rank different model forecasts of the same volcanic ash cloud: Chapter 24
Science and Products
- Data
- Publications
Filter Total Items: 53
Results of the eruptive column model inter-comparison study
This study compares and evaluates one-dimensional (1D) and three-dimensional (3D) numerical models of volcanic eruption columns in a set of different inter-comparison exercises. The exercises were designed as a blind test in which a set of common input parameters was given for two reference eruptions, representing a strong and a weak eruption column under different meteorological conditions. CompaAuthorsAntonio Costa, Yujiro Suzuki, M. Cerminara, Ben J. Devenish, T. Esposti Ongaro, Michael Herzog, Alexa R. Van Eaton, L.C. Denby, Marcus Bursik, Mattia de' Michieli Vitturi, S. Engwell, Augusto Neri, Sara Barsotti, Arnau Folch, Giovanni Macedonio, F. Girault, G. Carazzo, S. Tait, E. Kaminski, Larry G. Mastin, Mark J. Woodhouse, Jeremy C. Phillips, Andrew J. Hogg, Wim Degruyter, Costanza BonadonnaVolcanic lightning and plume behavior reveal evolving hazards during the April 2015 eruption of Calbuco volcano, Chile
Soon after the onset of an eruption, model forecasts of ash dispersal are used to mitigate the hazards to aircraft, infrastructure and communities downwind. However, it is a significant challenge to constrain the model inputs during an evolving eruption. Here we demonstrate that volcanic lightning may be used in tandem with satellite detection to recognize and quantify changes in eruption style anAuthorsAlexa R. Van Eaton, Álvaro Amigo, Daniel Bertin, Larry G. Mastin, Raúl E Giacosa, Jerónimo González, Oscar Valderrama, Karen Fontijn, Sonja A BehnkeAdjusting particle-size distributions to account for aggregation in tephra-deposit model forecasts
Volcanic ash transport and dispersion (VATD) models are used to forecast tephra deposition during volcanic eruptions. Model accuracy is limited by the fact that fine-ash aggregates (clumps into clusters), thus altering patterns of deposition. In most models this is accounted for by ad hoc changes to model input, representing fine ash as aggregates with density ρagg, and a log-normal size distributAuthorsLarry G. Mastin, Alexa R. Van Eaton, A.J. DurantHail formation triggers rapid ash aggregation in volcanic plumes
During explosive eruptions, airborne particles collide and stick together, accelerating the fallout of volcanic ash and climate-forcing aerosols. This aggregation process remains a major source of uncertainty both in ash dispersal forecasting and interpretation of eruptions from the geological record. Here we illuminate the mechanisms and timescales of particle aggregation from a well-characterizeAuthorsAlexa R. Van Eaton, Larry G. Mastin, M. Herzog, Hans F. Schwaiger, David J. Schneider, Kristi L. Wallace, Amanda B ClarkeEvidence for large compositional ranges in coeval melts erupted from Kīlauea's summit reservoir
Petrologic observations on Kīlauea's lavas include abundant microprobe analyses of glasses, which show the range of melts available in Kīlauea's summit reservoir over time. During the past two centuries, compositions of melts erupted within the caldera have been limited to MgO = 6.3–7.5 wt%. Extracaldera lavas of the 1959, 1971, and 1974 eruptions contain melts with up to 10.2, 8.9, and 9.2 wt% MgAuthorsRosalind T. Helz, David A. Clague, Larry G. Mastin, Timothy R. RoseElectron microprobe analyses of glasses from Kīlauea tephra units, Kīlauea Volcano, Hawaii
This report presents approximately 2,100 glass analyses from three tephra units of Kīlauea Volcano: the Keanakākoʻi Tephra, the Kulanaokuaiki Tephra, and the Pāhala Ash. It also includes some new analyses obtained as part of a re-evaluation of the MgO contents of glasses in two of the three original datasets; this re-evaluation was conducted to improve the consistency of glass MgO contents among tAuthorsRosalind L. Helz, David A. Clague, Larry G. Mastin, Timothy R. RoseCycles of explosive and effusive eruptions at Kīlauea Volcano, Hawai‘i
The subaerial eruptive activity at Kīlauea Volcano (Hawai‘i) for the past 2500 yr can be divided into 3 dominantly effusive and 2 dominantly explosive periods, each lasting several centuries. The prevailing style of eruption for 60% of this time was explosive, manifested by repeated phreatic and phreatomagmatic activity in a deep summit caldera. During dominantly explosive periods, the magma supplAuthorsDon Swanson, Timothy R. Rose, Adonara E Mucek, Michael O. Garcia, Richard S. Fiske, Larry G. MastinTesting the accuracy of a 1-D volcanic plume model in estimating mass eruption rate
During volcanic eruptions, empirical relationships are used to estimate mass eruption rate from plume height. Although simple, such relationships can be inaccurate and can underestimate rates in windy conditions. One-dimensional plume models can incorporate atmospheric conditions and give potentially more accurate estimates. Here I present a 1-D model for plumes in crosswind and simulate 25 historAuthorsLarry G. MastinModeling ash fall distribution from a Yellowstone supereruption
We used the volcanic ash transport and dispersion model Ash3d to estimate the distribution of ashfall that would result from a modern-day Plinian supereruption at Yellowstone volcano. The simulations required modifying Ash3d to consider growth of a continent-scale umbrella cloud and its interaction with ambient wind fields. We simulated eruptions lasting 3 days, 1 week, and 1 month, each producingAuthorsLarry G. Mastin, Alexa R. Van Eaton, Jacob B. LowensternUser’s guide and reference to Ash3d—A three-dimensional model for Eulerian atmospheric tephra transport and deposition
Ash3d is a three-dimensional Eulerian atmospheric model for tephra transport, dispersal, and deposition to study and forecast hazards of volcanic ash clouds and tephra fall. In this report, we explain how to set up simulations using a web interface, and how to view and interpret model output. We also summarize the architecture of the model and some of its properties.AuthorsLarry G. Mastin, Michael J. Randall, Hans F. Schwaiger, Roger P. DenlingerInjection, transport, and deposition of tephra during event 5 at Redoubt Volcano, 23 March, 2009
Among the events of the 2009 eruption at Redoubt Volcano, Alaska, event 5 was the best documented by radar, satellite imagery, and deposit mapping. We use the new Eulerian tephra transport model Ash3d to simulate transport and deposition of event 5 tephra at distances up to 350 km. The eruption, which started at about 1230 UTC on 23 March, 2009, sent a plume from the vent elevation (estimated at 2AuthorsLarry G. Mastin, Hans F. Schwaiger, David J. Schneider, Kristi L. Wallace, Janet Schaefer, Roger P. DenlingerA Bayesian method to rank different model forecasts of the same volcanic ash cloud: Chapter 24
Volcanic eruptions often spew fine ash high into the atmosphere, where it is carried downwind, forming long ash clouds that disrupt air traffic and pose a hazard to air travel. To mitigate such hazards, the community studying ash hazards must assess risk of ash ingestion for any flight path and provide robust and accurate forecasts of volcanic ash dispersal. We provide a quantitative and objectiveAuthorsRoger P. Denlinger, P. Webley, Larry G. Mastin, Hans F. Schwaiger - Software
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*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