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The role of groundwater in explosive eruptions: Insights from experiments and modeling

Susan Sakimoto 1,2 Alison Graettinger3, Ivana Torres-Ewert3, J. T. Parsons2, Alan Whittington4, Ingo Sonder2

  • Affiliations: 1Space Science Institute, 4765 Walnut St. Suite B, Boulder, CO 80301, USA; 2Department of Geology, 126 Cooke Hall, University at Buffalo, Buffalo, NY 14260-1350, USA; 3Department of Earth and Environmental Sciences, University of Missouri Kansas City, 5100 Rockhill Rd. Flarsheim Hall 420, Kansas City MO 641109, USA; 4Department of Earth and Planetary Sciences, The University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78255, USA

  • Presentation type: Talk [Invited]

  • Presentation time: Monday 14:15 - 14:30, Room R290

  • Programme No: 3.3.5

  • Theme 3 > Session 3

Abstract

Little is known about the quantitative parameters necessary to generate explosive interactions between magma and wet sediment. This study combines melt experiments, numerical modeling, and laboratory measurements to constrain these parameters. We conducted 13 remelted basaltic melt pours at SUNY Buffalo of 22-50 kg of melt into cone-shaped sediment piles with summit basins. We varied the host sediment grain size from sand to gravel and water content from dry (0-7% water) to saturated (>34-40% water). Each experiment had thermocouples below the summit basin in the sediment, several moisture sensors, multiple video, still, and infrared cameras, and a surrounding tarp for ejecta collection (for wet experiments). Each pour resulted in a summit basin lava pool, and temporary and permanent changes in the sediment contact zone. Of the 13 experiments, five produced ejecta. Of these, three had water tables maintained by surrounding impermeable barriers, and the other two had frozen saturated sediment. Despite the melt rock being essentially degassed due to several hours of melting, explosive behavior was still generated. Explosive behavior required several conditions: sufficient heat pulse from the melt volume, sufficient initial water supply, additional water able to flow through the sediment, and limited ability to vent generated steam except through the melt. Numerical modeling of the experiments (COMSOL multiphysics) shows that the relative supply and mobility of the water and steam within the sediment is key. Under the subset of conditions where steam can be forced into the melt, even a degassed melt can generate explosive behavior and ejecta.