The Fidelity of Glass Reentrants in Crystals: Witnesses of Decompression and Stalling of Magma in Conduits

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As more than 500 million people (9% of the world population) live within the maximum exposure range of a volcano, some of the most important questions for studying volcanic systems regard hazard monitoring and mitigation. However, much of the ability to define the type of risks posed by individual volcanoes relies on the challenging task of accurate interpretation of their eruptive products (e.g. pumice and ash), particularly crucial in systems that have not been historically active. This project aims to improve the ability to use eruptive products to interpret how large, explosive eruptions evolve over time. To accomplish this, the erupted products from the 1991 eruption of Mt. Pinatubo (Philippines) will be studied, one of the largest explosive eruptions observed in the 20th century. Through quantifying the timescales associated discrete phases of this eruption, the processes controlling the evolution of these violent events will be reconstructed. These results will be integrated into the dense seismic and visual records collected from Mt. Pinatubo, creating an unprecedented database for linking modern eruption monitoring data with a field-based approach typically used for interpreting historic deposits. In addition to these scientific impacts, this will support a woman who is a new NSF PI, and will support several graduate and undergraduate students. This project is jointly funded by Petrology & Geochemistry and the Established Program to Stimulate Competitive Research (EPSCoR).Mt. Pinatubo experienced several days of discrete, smaller sub-plinian explosions, which ramped up to the June 15th climatic eruption. Reconstructing the decompression history through the Mt. Pinatubo eruptive sequence, and pairing this information with the seismic record, could provide a remarkable advancement for linking a common monitoring technique with a readily applied petrographic tool. A quantitative record of magma decompression during the days of escalating activity will be obtained by measuring concentrations and gradients of volatiles (H2O, CO2, Cl, Li, F) preserved in reentrants (open melt pockets hosted in crystals) and coupling this information with microlite growth timescales. Through combining these methods with detailed sampling, an understanding for how long and where magma was stalled during breaks in explosive activity will be determined. Further information will come from decompression experiments, which will allow for testing all ascent-rate interpretations through simulations. This project involves collaborations with scientists at the United States Geological Survey, three universities within the U.S., and researchers in the Philippines. Ultimately, the dataset afforded by this project will allow us to ask whether one can see evidence for what ended up being an escalation in eruptive energy preserved within the erupted products.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.