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Quantifying Hydrothermal Contributions to Volcanic Deformation: The 2021 Unrest of Askja Volcano

Laure Brenot 1,Társilo Girona2, Hélène Le Mével3, Corentin Caudron1, Jifei Han4, Tom Winder5

  • Affiliations: 1G-Time, Université Libre de Bruxelles, Brussels, Belgium; 2Alaska Volcano Observatory, Geophysical Institute, University of Alaska Fairbanks, Fairbanks, USA; 3Earth and Planets Laboratory, Carnegie Institution for Science, Washington DC, USA; 4Department of Earth Sciences -- Bullard Labs, University of Cambridge, Cambridge, UK; 5University of Iceland, Reykjavík, Iceland.

  • Presentation type: Poster

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

  • Poster Board Number: 249

  • Programme No: 2.4.30

  • Theme 2 > Session 4

Abstract

Understanding the mechanisms driving volcanic deformation remains crucial for eruption forecasting. This study investigates the complex relationship between hydrothermal processes and volcanic deformation at Askja volcano (Iceland), where distinct phases of acceleration and deceleration with substantial cumulative surface uplift exceeding 80 cm have been recorded since August 2021. Specifically, we examine how mechanically coupled magmatic and hydrothermal systems contribute to the observed deformation phases at Askja by implementing a thermo-mechanical numerical model using COMSOL Multiphysics V6.2. Our numerical models compare a purely elastic approach with a visco-elastic model consisting of a viscoelastic crust containing a magmatic reservoir modeled as a porous medium and a shallow hydrothermal system. Magma intrusion is simulated through a time-varying mass flux at the base of the reservoir. The model incorporates temperature-dependent rheological properties, with distinct relaxation times and shear moduli assigned to the crustal, magmatic, and hydrothermal domains. Our results reveal that accounting for both viscoelastic behavior and hydrothermal processes reduces the estimated magma intrusion rates needed to explain the observed surface displacement patterns compared to our purely elastic approach. These findings demonstrate the critical role of hydrothermal processes in modulating surface expressions of volcanic unrest, providing a framework for more accurate interpretations of geodetic observations at volcanoes worldwide.