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Evaluating Second Boiling as a Driver of Overpressure and Surface Deformation in Volcanic Systems

Gregor Weber1,2, Juliet Biggs2, Alain Burgisser3, Catherine Annen4

  • Affiliations: 1 School of Ocean and Earth Science, University of Southampton, Southampton, UK 2 School of Earth Science, University of Bristol, Bristol, UK 3 ISTerre, Université Mont Blanc, Chambéry, France 4 Institute of Geophysics, Czech Academy of Sciences, Prague, Czech Republic 

  • Presentation type: Poster

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

  • Poster Board Number: 179

  • Programme No: 1.8.10

  • Theme 1 > Session 8

Abstract

Volatile exsolution during magma crystallization, commonly referred to as second boiling, is a long-recognized mechanism for overpressurizing subvolcanic magma reservoirs through the expansion of a free fluid phase. Recent petrological studies have highlighted the role of late-stage volatile saturation in the lead-up to explosive eruptions. Thermodynamic calculations indicate that this process can generate overpressures on the order of tens of megapascals, potentially triggering volcanic eruptions. However, these models often assume a uniform temperature-time cooling trajectory for magmatic systems, overlooking the complexity of whole-reservoir cooling dynamics. Here we investigate the interplay between second boiling and magma reservoir evolution, emphasizing how cooling rates and viscous relaxation influence overpressure development. We introduce a novel thermodynamic-thermal coupling framework that tracks the pressurization and deformation history of crustal-scale magma reservoirs. This approach incorporates magma and chamber compressibility, volatile redissolution upon pressurization, and varying magmatic fluxes and intrusion depths. The results reveal that compositional and thermal factors, including felsic crust and high-temperature viscoelastic aureoles, serve as first-order controls that favor the relaxation of overpressures rather than their generation over time. We apply our model to the 12.9 ka VEI-6 Laacher See eruption (Eifel Volcanic Field, Germany), which exhibits evidence of late-stage volatile saturation. Integrating zircon-based magma flux estimates, thermometry, thermodynamic and thermo-mechanical models, we assess whether volatile accumulation could have triggered the eruption and whether surface deformation patterns might have provided early warning.