Stealth pressurisation of boiling magma limits geodetic detectability of volcanic eruptions
Abstract
A C T Crystallisation-driven volatile exsolution (second boiling) is widely invoked to pressurise shallow magma reservoirs, yet its ability to generate eruption-triggering overpressure and detectable ground deformation is poorly quantified. We couple phase equilibria with thermal and viscoelastic models of sill-like intrusions to map pressure evolution and geodetic detectability of second boiling. Thermodynamic calculations for basaltic and rhyolitic magmas from Askja (Iceland) and Puyehue-Cordón Caulle (Chile) are embedded in conductive thermal models for thin (20 m) and thick (200 m) sills at 2-4 km depth, and the resulting volume changes and magma compressibility are propagated into pressurisation histories and volume-change rates. Hydrous magmatic sills can develop overpressures of 20-30 MPa on timescales of months to centuries, depending on initial sill size and crustal parameters, whereas relatively dry basalt undergoes cyclic behaviour with contraction followed by modest re-pressurisation. For a given composition and depth, thin and thick sills attain similar overpressures but differ by an order of magnitude in volume-change rate. Only small, volatile-rich sills exceed typical InSAR resolution thresholds. In felsic crust, viscoelastic relaxation further dampens overpressure and surface deformation, consistent with globally observed reduced deformation at arc volcanoes. Our results define a regime of "stealth" pressurisation in shallow hydrous reservoirs, in which magma emplaced centuries earlier may accumulate eruption-scale overpressure with little or no unrest detectable by short temporal baseline geodetic monitoring. This mechanism can help explain unexpected explosive eruptions with little precursory deformation.
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BibTeX
@article{weber2026stealth,
title = {{Stealth pressurisation of boiling magma limits geodetic detectability of volcanic eruptions}},
author = {Gregor Weber and Juliet Biggs and Alain Burgisser and Catherine Annen},
journal = {Earth and Planetary Science Letters},
year = {2026},
month = oct,
doi = {10.1016/j.epsl.2026.120391},
url = {https://hal.science/hal-05858076v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Stealth pressurisation of boiling magma limits geodetic detectability of volcanic eruptions
AU - Gregor Weber
AU - Juliet Biggs
AU - Alain Burgisser
AU - Catherine Annen
PY - 2026
DA - 2026/10/09
JO - Earth and Planetary Science Letters
DO - 10.1016/j.epsl.2026.120391
UR - https://hal.science/hal-05858076v1
AB - A C T Crystallisation-driven volatile exsolution (second boiling) is widely invoked to pressurise shallow magma reservoirs, yet its ability to generate eruption-triggering overpressure and detectable ground deformation is poorly quantified. We couple phase equilibria with thermal and viscoelastic models of sill-like intrusions to map pressure evolution and geodetic detectability of second boiling. Thermodynamic calculations for basaltic and rhyolitic magmas from Askja (Iceland) and Puyehue-Cordón Caulle (Chile) are embedded in conductive thermal models for thin (20 m) and thick (200 m) sills at 2-4 km depth, and the resulting volume changes and magma compressibility are propagated into pressurisation histories and volume-change rates. Hydrous magmatic sills can develop overpressures of 20-30 MPa on timescales of months to centuries, depending on initial sill size and crustal parameters, whereas relatively dry basalt undergoes cyclic behaviour with contraction followed by modest re-pressurisation. For a given composition and depth, thin and thick sills attain similar overpressures but differ by an order of magnitude in volume-change rate. Only small, volatile-rich sills exceed typical InSAR resolution thresholds. In felsic crust, viscoelastic relaxation further dampens overpressure and surface deformation, consistent with globally observed reduced deformation at arc volcanoes. Our results define a regime of "stealth" pressurisation in shallow hydrous reservoirs, in which magma emplaced centuries earlier may accumulate eruption-scale overpressure with little or no unrest detectable by short temporal baseline geodetic monitoring. This mechanism can help explain unexpected explosive eruptions with little precursory deformation.
SN - 0012-821X
ER -