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Laboratory evidence for subsurface steam transport driving thermal anomalies at active volcanoes

^^Noé García-Martínez^1^, Társilo Girona2, David Benavente1

  • Affiliations: 1Department of Earth and Environmental Sciences, University of Alicante, Alicante, Spain; 2Alaska Volcano Observatory, Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK, USA

  • Presentation type: Poster

  • Presentation time: Monday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 251

  • Programme No: 2.4.31

  • Theme 2 > Session 4

Abstract

Understanding gas transport from depth to the surface is crucial to interpret signals at volcanoes, and allows eruption forecasting. A potential signal is the low-temperature geothermal anomaly, which may appear before an eruption (Girona et al., 2021; https://doi.org/10.1038/s41561-021-00705-4). However, the interactions between steam flow, H2O condensation, and heat transfer in active magmatic-hydrothermal systems are poorly understood, and many questions remain open. For example, could subsurface condensation of magmatic and/or hydrothermal steam drive satellite-detected thermal anomalies at the surface of volcano-hydrothermal systems? How do porous media properties and flow conditions contribute to the heat propagation towards the Earth's surface? To address these questions, a novel experimental setup was designed to inject hot steam at constant flow rate into the bottom of a sand column. We monitored temperature variations at the top of the column using a thermal infrared camera (satellite analogue) and also along its vertical profile using thermocouples. We characterized the influence of the inflow rate, inflow temperature, sand initial volumetric water content, and column height (proxy for condensation depth). Our results reveal that the injected steam exchanges heat with the porous material, condensing, and releasing latent heat, which migrates to the column surface via advection and conduction, yielding a thermal anomaly. In addition, we analysed the results with a Finite Element Method-based numerical model coupling Darcy's Law and energy conservations using COMSOL Multiphysics. Our model is able to reproduce the vertical temperature distribution along the column and the detection time of the surface thermal anomalies under most laboratory conditions.