Rheologic controls on the magnitude and mechanisms of outgassing in silicic lavas
Description
Data accompanying manuscript of the same name. The volume of pressurized gas trapped in bubbles in silicic lavas dictates the hazard they pose. Trapped gas can be liberated from the lava (outgassing) if pathways form to connect bubbles to the atmosphere. We present results of deformation experiments conducted on synthetic bubbly-lavas that (1) measure the amount of syn-deformation outgassing when pathways form by different processes (coalescence, shear-induced connectivity, melt fracturing), and (2) determine the influence of flow conditions, parameterized by the Weissenberg number (Wi), on the mechanism of outgassing. At low Wi (≤10-7) bubble coalescence facilitates near-complete outgassing. At intermediate Wi (10-6 to 10-4) no outgassing occurs unless the sample is highly-strained and shear-induced connectivity allows localized outgassing. At high Wi (≥10-2) melt-fracturing creates pathways that only permit limited outgassing. We use the results to fit an empirical model that predicts outgassing extent as a function of strain and Wi. Our results suggest extensive outgassing necessitates coalescence, which requires a lava remain hot and/or deforming at a low strain rate. Included in data repository: - experimental log, including conditions of experiment, sample dimensions and measured skeletal volumes - mechanical data for all deformation experiments and rate-stepping experiments used to determine stress exponent - codes and .mat files used to process mechanical data - photos of intact samples - scans of cut samples - binarized bubble traces used to calculate bubble numbers
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Institutions
- Rice UniversityTexas, Houston