Birth of a large volcanic edifice offshore Mayotte via lithosphere-scale dyke intrusion

Volcanic eruptions shape Earth’s surface and provide a window into deep Earth processes. How the primary asthenospheric melts form, pond and ascend through the lithosphere is, however, still poorly understood. Since 10 May 2018, magmatic activity has occurred offshore eastern Mayotte (North Mozambique channel), associated with large surface displacements, very-low-frequency earthquakes and exceptionally deep earthquake swarms. Here we present geophysical and marine data from the MAYOBS1 cruise, which reveal that by May 2019, this activity formed an 820-m-tall, ~5 km³ volcanic edifice on the seafloor. This is the largest active submarine eruption ever documented. Seismic and deformation data indicate that deep (>55 km depth) magma reservoirs were rapidly drained through dykes that intruded the entire lithosphere and that pre-existing subvertical faults in the mantle were reactivated beneath an ancient caldera structure. We locate the new volcanic edifice at the tip of a 50-km-long ridge composed of many other recent edifices and lava flows. This volcanic ridge is an extensional feature inside a wide transtensional boundary that transfers strain between the East African and Madagascar rifts. We propose that the massive eruption originated from hot asthenosphere at the base of a thick, old, damaged lithosphere.

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Supplementary Sections 1–3, Figs. 2.1–2.18 and Tables 1.1, 1.2, 2.1, 2.2 and 3.1–3.3.
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3D flight-through over the NVE and the acoustic plume.
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3D flight-through over the upper insular shelf of Mayotte, the Horseshoe and the acoustic plumes.
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Feuillet Nathalie, Jorry Stephan, Crawford Wayne C., Deplus Christine, Thinon Isabelle, Jacques Eric, Saurel Jean Marie, Lemoine Anne, Paquet Fabien, Satriano Claudio, Aiken Chastity, Foix Oceane, Kowalski Philippe, Laurent Angèle, Rinnert Emmanuel, Cathalot Cecile, Donval Jean-Pierre, Guyader Vivien, Gaillot Arnaud, Scalabrin Carla, Moreira Manuel, Peltier Aline, Beauducel François, Grandin Raphaël, Ballu Valérie, Daniel Romuald, Pelleau Pascal, Gomez Jérémy, Besançon Simon, Geli Louis, Bernard Pascal, Bachelery Patrick, Fouquet Yves, Bertil Didier, Lemarchand Arnaud, van der Woerd Jérome (2021). Birth of a large volcanic edifice offshore Mayotte via lithosphere-scale dyke intrusion. Nature Geoscience. 14 (10). 787-795.,

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