Alteration-Induced Volcano Instability at La Soufriere de Guadeloupe (Eastern Caribbean)

M. J. Heap, Tobias Baumann, Marina Rosas-Carbajal, J-C. Komorowski, H. A. Gilg, Marlene Villeneuve, R Moretti, Patrick Baud, Lucille Carbillet, Claire Harnett, Thierry Reuschlé

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Abstract

Volcanoes are unstable structures that deform laterally and frequently experience mass wasting events. Hydrothermal alteration is often invoked as a mechanism that contributes significantly to volcano instability. We present a study that combines laboratory experiments, geophysical data, and large-scale numerical modeling to better understand the influence of alteration on volcano stability, using La Soufrière de Guadeloupe (Eastern Caribbean) as a case study. Laboratory experiments on variably altered (advanced argillic alteration) blocks show that uniaxial compressive strength, Young's modulus, and cohesion decrease as a function of increasing alteration, but that the internal friction angle does not change systematically. Simplified volcano cross sections were prepared (a homogenous volcano, a volcano containing the alteration zone identified by a recent electrical survey, and a volcano with an artificially enlarged area of alteration) and mechanical properties were assigned to zones corresponding to unaltered and altered rock. Numerical modeling performed on these cross sections, using a hydro-thermo-mechanical modeling code, show (a) the importance of using upscaled values in large-scale models and (b) that alteration significantly increases volcano deformation and collapse volume. Finally, we combined published muon tomography data with our laboratory data to create a 3D strength map, exposing a low-strength zone beneath the southern flank of the volcano coincident with the hydrothermal system. We conclude that hydrothermal alteration decreases volcano stability and thus expedites volcano spreading and increases the likelihood of mass wasting events and associated volcanic hazards. Hydrothermal alteration, and its evolution, should therefore be monitored at active volcanoes worldwide.

OriginalspracheEnglisch
Aufsatznummere2021JB022514
FachzeitschriftJournal of geophysical research
Jahrgang126
Ausgabenummer8
DOIs
PublikationsstatusVeröffentlicht - Aug. 2021

Bibliographische Notiz

Funding Information:
This work was supported by the TelluS Program of INSU-CNRS (?Assessing the role of hydrothermal alteration on volcanic hazards?) and ANR grant MYGALE (?Modeling the phYsical and chemical Gradients of hydrothermal ALteration for warning systems of flank collapse at Explosive volcanoes?), awarded to the first author. M. Heap also acknowledges support from the Institut Universitaire de France (IUF). We thank Tomaso Esposti Ongaro, Gilles Morvan, Christophe Nevado, Marie Cherrier, Oc?ane Rocher, and Lisa Tomasetto. We thank the IPGP for general funding for the Observatoires Volcanologiques et Sismologiques (OVS), INSU-CNRS for the funding provided by the Service National d'Observation en Volcanologie (SNOV), and the Minist?re pour la Transition Ecologique (MTE) for financial support for the monitoring of the instable flank of La Soufri?re de Guadeloupe. This study contributes to the IdEx Universit? de Paris ANR-18-IDEX-0001. Olivier Roche, Jessica Ball, and Gabor Kereszturi are thanked for providing comments that helped improve this manuscript.

Funding Information:
This work was supported by the TelluS Program of INSU‐CNRS (“Assessing the role of hydrothermal alteration on volcanic hazards”) and ANR grant MYGALE (“Modeling the phYsical and chemical Gradients of hydrothermal ALteration for warning systems of flank collapse at Explosive volcanoes”), awarded to the first author. M. Heap also acknowledges support from the Institut Universitaire de France (IUF). We thank Tomaso Esposti Ongaro, Gilles Morvan, Christophe Nevado, Marie Cherrier, Océane Rocher, and Lisa Tomasetto. We thank the IPGP for general funding for the Observatoires Volcanologiques et Sismologiques (OVS), INSU‐CNRS for the funding provided by the Service National d'Observation en Volcanologie (SNOV), and the Ministère pour la Transition Ecologique (MTE) for financial support for the monitoring of the instable flank of La Soufrière de Guadeloupe. This study contributes to the IdEx Université de Paris ANR‐18‐IDEX‐0001. Olivier Roche, Jessica Ball, and Gabor Kereszturi are thanked for providing comments that helped improve this manuscript.

Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.

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