EGU21-3204
https://doi.org/10.5194/egusphere-egu21-3204
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

From permanent flank sliding to catastrophic collapse and explosive eruptions at basaltic volcanoes: the role of shallow intrusive magma bodies.

Andrea Di Muro1,2, Ulrich Kueppers3, Michael Heap4, Fabian Scharzlmueller3, and Donald Dingwell3
Andrea Di Muro et al.
  • 1Université de Paris, Institut de physique du globe de Paris, CNRS, F-75005 Paris, France
  • 2Observatoire volcanologique du Piton de la Fournaise, Institut de physique du globe de Paris, F-97418 La Plaine des Cafres, France
  • 3Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität München, Theresienstraße 41, 80333 Munich, Germany
  • 4Géophysique Expérimentale, Institut de Physique de Globe de Strasbourg (UMR 7516 CNRS, Université de Strasbourg/EOST), 5 rue René Descartes, 67084 Strasbourg cedex, France

Caldera collapses and flank failures, eventually associated with violent explosive eruptions, punctuate the history of volcanoes worldwide and represent major highly hazardous events in their evolution. Nevertheless, their link to magma transfer and storage in the plumbing system, together with the nature of weakness zones responsible for volcano collapses still need to be fully elucidated. We performed rapid decompression experiments on a set of basaltic rocks (lavas, dolerite dikes, gabbros) from Piton de la Fournaise, La Réunion, spanning a very large range of petrophysical properties. Samples derived from the most recent  caldera-related explosive breccias of this volcano. Petrophysical measurements revealed a corresponding variability in density, porosity, P-wave velocity (dry and wet), and uniaxial compressive strength. The large variation in P-wave velocity and strength is interpreted to be the result of the wide ranges in texture (porosity/vesicularity) and lithology. Notably, some of the dense gabbroic units that have remained intact despite likely having experienced several natural cycles of heating and cooling are comparatively weak. We infer that volcano instability should not be interpreted solely in terms of altered rock units. On one side, the interface between shallow intrusive bodies and the vesicular lava pile represents a potential interface for repeated sill emplacement, which favour flank sliding. On the other side, weak shallow seated granular intrusive rocks with variable amounts of interstitial melt respond in a brittle fashion to rapid decompression during caldera and flank collapse events. The large petrophysical heterogeneity of crustal rocks together with the occurrence of shallow intrusive bodies must be considered when interpreting monitoring data and assessing potential hazards related to the stability of basaltic volcanoes.

How to cite: Di Muro, A., Kueppers, U., Heap, M., Scharzlmueller, F., and Dingwell, D.: From permanent flank sliding to catastrophic collapse and explosive eruptions at basaltic volcanoes: the role of shallow intrusive magma bodies., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3204, https://doi.org/10.5194/egusphere-egu21-3204, 2021.

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