Collaborative Research: Degassing-Based Constraints on the Dynamics of Submarine Eruptions

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The dynamics (ascent rate, mass eruption rate, lava flow rate, etc.) of submarine eruptions, which account for roughly 70% of the Earth's annual volcanic activity, are essentially unknown. This research will develop a degassing-based "geospeedometer" (i.e., a method for determining how fast magma moves from its magma chamber to its final resting place on the sea floor). for mid-ocean ridge basalts that will allow quantification of eruption dynamics in Earth's largest volcanic system (i.e., the mid-ocean ridge spreading centers) and help to evaluate how those dynamics impact carbon fluxes from the vast mid-ocean ridge system. A combination of detailed microanalysis of textures and volatiles in lava samples from submarine volcanic lava flows and a unique set of laboratory experiments will be used to quantify the mechanisms and rates of degassing and vesiculation in mid-ocean ridge basalts. A "geospeedometer" will be developed on the basis of those results. This geospeedometer will allow us to understand and measure flow rates of mid-ocean ridge lavas, decompression rates of the eruptions feeding them, and how flow morphologies (sheet flow vs. pillow lava) reflect eruption rate. Analyses will be focused on samples from the well mapped and comprehensively sampled 2011 eruption of Axial Volcano on the Juan de Fuca Ridge off the northwest coast of the US and Canada. Samples from this eruption will be analyzed for degassing via volatile concentrations and vesicle-size distributions of samples collected along the Axial Volcano eruptive fissures and flow paths. A central challenge will be the linking of temerature, depressurization rate, and composition to volatile concentrations and vesicle populations. Thus, a series of laboratory decompression and cooling experiments using natural, CO2-supersaturated, mid-ocean ridge basalts will be undertaken to provide insights and input parameters for model calculations, leading to the quantification of results. the 2011 eruption of Axial Volcano will serve as the test case and be used to refine models of degassing and provide the vehicle for incorporating research reesults into broadly applicable models for submarine volcanic systems. The research will also help improve estimates of carbon flux by evaluating more rigorously and quantitatively the controls on seafloor basalt degassing of CO2. Broader impacts of the research include support of graduate and undergraduate students and engagement of the investigators with K-12 STEM teachers via already plannedteacher training workshops. Research will also be incorporated into courses taught by the investigators and data will be made freely available to the public through NSF-funded data management facilities.