Ph.D., University of Rhode Island, 1995
“Submarine Pyroclastic Deposits: Implications for Pyroclastic Flow/Seawater Interactions and Volatile Discharge During Explosive Volcanic Eruptions”
Dr. Charles W. Mandeville is a volcanologist and geochemist. He is Associate Program Coordinator for Volcano Hazards at the United States Geological Survey (USGS, http://volcanoes.usgs.gov). He conducts research in physical volcanology, petrology of volcanic rocks and applies stable isotope geochemical techniques to volcanic degassing and elemental cycling. His Ph.D. research on the catastrophic eruption of Krakatau Volcano, Indonesia investigated the physical volcanology, petrology and geochemistry of the 1883 deposits preserved on land and on the sea floor surrounding the volcano. Results of this research indicated that entrance of pyroclastic flows into the sea during the 1883 eruption was the cause of lethal tsunamis.
Exsolution of volatiles (H2O, CO2, S, Cl, F) from magma generates overpressure in crustal magma chambers and drives volcanic eruptions. Dr. Mandeville measures dissolved H2O and CO2 in melt inclusions and matrix glasses by infrared spectroscopy and S, Cl, F by electron microprobe or secondary ionization mass spectrometry (SIMS). He combines magmatic volatiles data with stable isotopes of sulfur, oxygen and hydrogen from the same samples to delineate the ultimate sources of magmatic volatiles, zones of magma storage in the crust, and extents and styles of degassing. Dr. Mandeville is particularly interested in how degassing style indicated by stable isotope data correlates with magma ascent rates and explosive or effusive eruptive activity. Integrated volatiles and stable isotope studies of the Krakatau and Mt. Mazama (current site of Crater Lake, Oregon) eruptions identified the mantle as the ultimate source of dissolved volatiles and the large modifications of initial sulfur and hydrogen isotopic signatures that can result from degassing as documented from samples spanning each of the deposit stratigraphies.
Dr. Mandeville continues to conduct U.S. National Science Foundation supported research on recycling of sulfur in subduction zone magmatism by conducting in situ sulfur isotopic measurements of melt inclusions utilizing secondary ionization mass spectrometry (SIMS) and X-ray absorption near edge structure spectroscopy (XANES) for best estimates of initial isotopic composition and sulfur and iron speciation and oxidation state in mafic melt inclusions from a number of arc volcanoes as well as experimental run products from high temperature sulfur isotope fractionation experiments.