Experiment Versus Nature: Testing Models of Magma Storage and Movement from the 2006 Eruption of Augustine Volcano, Alaska

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Intellectual Merit: Recent, well-monitored volcanic eruptions serve as excellent "natural laboratories",allowing diverse researchers to collaborate in resolving questions about how to use geophysical precursors to predict eruptive activity. The 2006 eruption of Augustine Volcano, Alaska represents an excellent target for experimental petrology studies to constrain magma storage and ascent dynamics, within a framework of robust geodetic and seismic observations of precursory and syn-eruptive activity and eruptive timescales. Details about the 2006 eruption activity and its deposits will be augmented by experimental studies to develop a petrology- and geochemistry-based model for storage of a largely crystalline, high-silica andesite "mush" body at 4-6 km depth beneath the volcano. Basaltic replenishment and limited hybridization (i.e., magma mixing) produced a low-silica andesite magma, and re-mobilization of the "mush" apparently triggered the eruption. The early explosive phase of the eruption mainly involved the low-silica andesite, which shows petrologic evidence for stalling or storage at ~25 MPa prior to the onset of the eruption. Starting in mid-November, 2005, geodetic data show evidence for dike injection into the shallow crust beneath Augustine, with the eruption ensuing in mid-January. This timescale is also constrained to first order by the widths of amphibole reaction rims found in the low-silica andesite, indicating that ascent to depths shallower than amphibole stability in that magma coincided with the onset of the dike injection. The proposed project would provide experimental constraints on magma storage and ascent rates for the low and high-silica andesite end member magmas: 1. Phase equilibria constraints on magma storage conditions of the high-silica andesite. 2. Continuous rate decompression experiments to constrain plagioclase crystallization kinetics in the low-silica andesite, to decipher the timing of early dike injection leading to the onset of the eruption. 3. Experimentally constrain amphibole breakdown reaction rates, to estimate both magma ascent rates and heating timescales related to magma mixing and hybridization. These tasks will be combined to formulate a model that links the experimental with the geophysical observations, and ultimately to enhance volcano monitoring using precursor geophysical indicators.Broader Impacts: This project support the research activities of one PhD student (Sarah Henton), Ms. Henton's experience with the Montserrat Volcano Observatory and Soufriere Hills Volcano will be beneficial to the project. The project will also support and enhance the research of three females in the geosciences. Through the connections of the PI and collaborator with the Alaska Volcano Observatory, the results will be disseminated to the public living near Augustine, in the Kenai Peninsula. The results will also be used to cross-link with geophysical data from monitoring activities in 2006, to decipher the source mechanisms of geodetic and seismic signals related to specific phases of the eruption.