Tiltmeter analysis of Mount St. Helens, Skamania County, Washington

Brown, Edward Charles

doi:10.15760/etd.5017

Cited by 1 publication

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References 11 publications

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“…Volcano deformation versus CO 2 in the excess fluid. Volumetric deformation (∆ V ) is estimated using the point pressure model for magma reservoir (Dzurisin, 2003; Mogi, 1958; Masterlark, 2007) based on volcano deformation measured using InSAR (Bignami et al., 2014; Lee, Lu, Jung, Won, & Dzurisin, 2010; Surono et al., 2012), electronic distance measurement (EDM) and global position system (GPS; Jackson, Shepherd, Robertson, & Skerritt, 1998; Shepherd, Herd, Jackson, & Watts, 1998; Voight et al, 1998), dry tilt (Brown, 1984; McKee, Itikarai, & Davies, 2017; Newhall et al., 2017) and dry tilt and EDM (Banks, Carvajal, Mora, & Tryggvason, 1990). ∆ V is normalized to the volume of erupted magma (reported as Dense Rock Equivalent or DRE ; Figure 1); ∆ V/DRE is, therefore, the measured volumetric strain induced by gas accumulation in the shallow magma reservoir prior to volcanic eruption.…”

Section: Discussionmentioning

confidence: 99%

CO₂ favours the accumulation of excess fluids in felsic magmas

2020

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Deformation and gas emissions at active volcanoes provide insights into volcanic plumbing systems. Large discrepancies are observed between the volumes calculated from deformation data and the volumes of erupted magmas and are ascribed to the amount of excess fluids in magma reservoirs, which hinders our capacity to predict the magnitude of an imminent eruption. Here, a series of experiments demonstrates that the amount of trapped excess fluids in felsic magmas depends strongly on fluid composition. Magmas with CO2 excess fluids become permeable at 44% larger porosities with respect to the H2O‐rich counterparts at equivalent crystallinity. Available excess gas geochemistry and juvenile porosity data from felsic systems reveal that the volume discrepancy between erupted magma and syn‐eruptive SO2 increases with CO2 excess in magmas. These data highlight that CO2‐rich fluids enhance magma's capacity to store excess volatiles and shed light on the largest discrepancies between pre‐eruptive deformation and eruption intensity and magnitude.

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