EGU2020-11307
https://doi.org/10.5194/egusphere-egu2020-11307
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Birth of a large volcanic edifice offshore Mayotte (Comoros Island, Western Indian Ocean)

Nathalie Feuillet1, Stephan Jorry2, Wayne Crawford1, Christine Deplus1, Isabelle Thinon3, Eric Jacques1, Jean-Marie saurel1, Anne Lemoine3, Fabien Paquet3, Claudio Satriano1, Chastity Aiken2, Angèle Laurent1, Cecile Cathalot2, Emmanuel Rinnert2, Arnaud Gaillot2, Carla Scalabrin2, Manuel Moreira1, Aline Peltier1, François Beauducel1, Valerie Ballu4, and the Tellus SISMAYOTTE and MAYOBS Team*
Nathalie Feuillet et al.
  • 1Université de Paris, Institut de physique du globe de Paris, CNRS, F-75005 Paris, France
  • 2IFREMER, Unité Géosciences Marines, Technopole La Pointe du Diable, 29280 Plouzané, France
  • 3Bureau de Recherches Géologiques et Minières - BRGM, DGR/GBS, F-45060 Orléans, France
  • 4LIttoral ENvironnement et Sociétés (LIENSs) UMR7266, Université de La Rochelle - CNRS, 2 rue Olympe de Gouges, 17000 La Rochelle
  • *A full list of authors appears at the end of the abstract

Volcanic eruptions are foundational events shaping the Earth’s surface and providing a window into deep Earth processes. We document here an ongoing magmatic event offshore Mayotte island (Western Indian Ocean) unprecedented in terms of emitted volume of lava and duration of the seismic crisis.This event gave birth to a deep-sea volcanic edifice 820m tall and ~ 5 km3 in volume, located 50 km from Mayotte. A plume with distinct chemical signatures compared to open-ocean seawater emanated from the edifice, generating an exceptional 1900m-high vertical acoustic anomaly in the water column. Noble gas analyses in the vesicles from a popping rock dredged on the flank of the edifice, indicate rapid magma transfer from the asthenosphere. The edifice is located at the tip of a WNW-ESE–striking volcanic ridge composed of many other edifices, cones and lava flows constructed by past eruptions. Starting in May 2018 thousand of earthquakes were triggered by the magmatic event. The space-time distribution of the seismicity suggests that magma below the center of the ridge was transported to the new edifice over a few weeks in dikes that penetrated the brittle mantle a result of a lithosphere-scale extensional episode accommodating motion along a transfer zone between the East-African rifts and Madagascar. Since the eruption’s onset, the seismicity is mostly concentrated closer to the island, in an exceptionally deep zone (25-50 km) overlain by a zone of enigmatic, very low frequency, tremors.

Tellus SISMAYOTTE and MAYOBS Team:

Océane Foix, Philippe Kowalski, Jean-Pierre Donval, Vivien Guyader, Raphael Grandin, Romuald Daniel, Patrice Pelleau, Jeremy Gomez, Simon Besançon, Louis Geli, Pascal Bernard, Patrick Bachelery, Yves Fouquet, Didier Bertil, Arnaud Lemarchand, Jérome Van der Woerd.

How to cite: Feuillet, N., Jorry, S., Crawford, W., Deplus, C., Thinon, I., Jacques, E., saurel, J.-M., Lemoine, A., Paquet, F., Satriano, C., Aiken, C., Laurent, A., Cathalot, C., Rinnert, E., Gaillot, A., Scalabrin, C., Moreira, M., Peltier, A., Beauducel, F., and Ballu, V. and the Tellus SISMAYOTTE and MAYOBS Team: Birth of a large volcanic edifice offshore Mayotte (Comoros Island, Western Indian Ocean), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11307, https://doi.org/10.5194/egusphere-egu2020-11307, 2020

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Presentation version 1 – uploaded on 08 May 2020
  • CC1: Questions and answers from the live chat during EGU2020, Michael Heap, 11 May 2020

    Q: Any constraints on the plumbing system?

    A: Study from Lemoine et al. and Cesca et al., infer a deep subcrustal reservoir

    Q: Could you give us an update on what is going on now in Mayotte?

    A: An important seismo-volcanic crisis is on going off Mayotte Island. The BRGM (Lemoine et al., 2019) and the REVOSIMA (the new observatory in Mayotte,  recorded more than 7000 earthquakes offshore, east of the coasts. Since July 2018, the island subsides and moves eastwards at exceptional rates of up to 20 cm/year, as a result of a large reservoir deflation located 30 km far from the island’s coast (Lemoine et al., 2019, Cesca et al., 2020).

    Q: Will your Nat paper include any source modeling (analytical, FEM...)?

    A: Yes we made some simple models of the deformation and our results also show a deep reservoir