RAPID: Lethal pyroclastic density current (PDC) generation and transport at Fuego volcano

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This Rapid Research Response (RAPID) award will be used to better understand the deadly eruption at Fuego volcano (Guatemala) on June 3rd, 2018, and in particular the pyroclastic density currents (PDCs) that caused the fatalities. How those PDCs initiated, what caused them to move that far, and what could be the conditions under which they may form in the future, are all poorly understood issues. By looking at the PDCs deposit, mapping them and study their stratigraphy in the field, analyzing the the chemical, petrological, and physical characteristics (density and vesicularity, grain size distribution, etc.), and by using numerical models to understand their flowing dynamics, this team hopes to be able to tell where the PDCs material came from, and how it was fragmented and transported. They will also look at geophysical and geochemical monitoring data leading up and during the eruption, particularly from the local seismic network and satellite remote sensing data, to characterize other aspects of the eruption as well (eruption intensity and duration) and put the PDC information in that context. This knowledge will improve our understanding of the formation of this kind of PDCs, particularly at basaltic volcanoes like Fuego, and could be relevant to many other similar volcanoes worldwide and in the US.This RAPID award will support fieldwork mapping, stratigraphy and facies associations determination, UAV based photogrammetry of the deposits and potential source area, and sample collection of the PDC and airfall tephra deposits. Laboratory analysis of samples collected in the field will aim to characterize the grain size distribution, shape, density and vesicularity of PDCs and tephra components, as well as geochemical (major and trace element analysis) and petrographic and microtextural characteristics. Field and laboratory work will allow to infer the source process (e. g. column vs. upper slope deposits collapse) in terms of location, volume and duration. Numerical modeling (VolcFlow and Titan2D) of the PDCs propagation over realistic terrain topography (high resolution DEMs), constrained by deposit mapping and volume estimations, and the geophysical data on timing and duration on flow initiation and propagation will be conducted to find the best fit model parameters and infer the flow dynamics (e. g. velocity, mass flow rate, volume partition in pulses, etc.). The research will be conducted in close collaboration with Guatemalan volcano monitoring agency INSIVUMEH (Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hidrologia) and the study's conclusions will be highly informative to INSIVUMEH's efforts to monitor and forecast similar events in the future, and the potential use of similar models to be incorporated in the hazard assessment process. The results will also be relevant to our understanding of eruptive processes (and their deposits) at other similar basaltic volcanoes worldwide, in particular the generation of block-and-ash flow type PDCs and associated deposits, and the hazards linked to them.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.