From prodigious volcanic degassing to caldera subsidence and quiescence at Ambrym (Vanuatu): the influence of regional tectonics

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1038/s41598-019-55141-7.

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Authors

Tara Shreve , Raphaël Grandin , Marie Boichu, Esline Garaebiti, Yves Moussallam, Valérie Ballu, Francisco Delgado, Frédérique Leclerc, Martin Vallée, Nicolas Henriot

Abstract

Eruptive activity shapes volcanic edifices. The formation of broad caldera depressions is often associated with major collapse events, emplacing conspicuous pyroclastic deposits. However, caldera subsidence may also proceed silently by magma withdrawal at depth, more difficult to detect. Ambrym, a basaltic volcanic island, hosts a 12-km wide caldera and several intensely-degassing lava lakes confined to intra-caldera cones. Using satellite remote sensing of deformation, gas emissions and thermal anomalies, combined with seismicity and ground observations, we show that in December 2018 an intra-caldera eruption at Ambrym preceded normal faulting with >2 m of associated uplift along the eastern rift zone and 2.5 m of caldera-wide subsidence. Deformation was caused by lateral migration of >0.4 cubic kilometers of magma into the rift zone, extinguishing the lava lakes, and feeding a submarine eruption in the rift edge. Recurring rifting episodes, favored by stress induced by the D’Entrecasteaux Ridge collision against the New Hebrides arc, lead to progressive subsidence of Ambrym’s caldera and concurrent draining of the lava lakes. Although counterintuitive, convergent margin systems can induce rift zone volcanism and subsequent caldera subsidence.

DOI

https://doi.org/10.31223/osf.io/c8d5v

Subjects

Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology

Keywords

remote sensing, volcanology, Tectonics

Dates

Published: 2019-06-28 15:01

Last Updated: 2019-10-24 13:05

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License

CC BY Attribution 4.0 International

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