EGU2020-11026, updated on 20 Apr 2021
EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Early development of a deep sea volcano offshore Mayotte revealed by seafloor mapping : first results from the MAYOBS cruises

Christine Deplus1, Nathalie Feuillet1, Isabelle Thinon2, Stephan Jorry3, Yves Fouquet3, Patrick Bachèlery4, Sylvain Bermell3, Florian Besson3, Manon Bickert1, Arnaud Gaillot3, Charline Guérin3, Anne Le Friant1, Fabien Paquet2, Delphine Pierre3, and Mathilde Pitel-Roudaut3
Christine Deplus et al.
  • 1Université de Paris, Institut de Physique du Globe de Paris, CNRS, Paris, France (
  • 2BRGM, DGR/GBS, Orléans, France
  • 3IFREMER, Géosciences Marines, Plouzané, France
  • 4Université Clermont-Auvergne, CNRS, IRD, OPGC, Clermont Ferrand, France

The early development and growth of seamounts are poorly known as the birth of a volcano on the sea bottom has been rarely observed. The on-going Mayotte seismo-volcanic crisis is associated with the formation of a new seafloor volcano at a water depth of 3300 m and provides the opportunity to study its early development.

Four oceanographic cruises, MAYOBS 1 to 4, were carried out between May and July 2019 aboard the French R/V Marion Dufresne. High resolution bathymetry and backscatter data as well as sub-bottom profiler, gravity and magnetic profiles were collected during each cruise. A dense network of profiles has been achieved over the new volcano at different epochs, allowing to assess its detailed morphology and the evolution through time. During MAYOBS4, a deep-towed underwater camera provided sea bottom videos and photos on the volcano.

First results indicate that the new volcano is still growing at the end of July 2019. Repetitive surveys in May, June and July 2019 allow to document the morphological evolution of the volcano, to estimate the volume of material emplaced between each epoch and to discuss the emitted lava rate.

The new volcano has a starfish shape and is now 820 m high. Steep slopes are observed close to the summit and several radial ridges developed from its central part, displaying hummocky morphology similar to the ones observed along mid oceanic axial volcanic ridges. At the bottom, flat areas with high backscatter could indicate channelized lava flows emplaced at higher effusion rates. The morphological analysis combined with video imagery brings constraints to the eruptive processes yielding to the formation of a nascent volcano.


How to cite: Deplus, C., Feuillet, N., Thinon, I., Jorry, S., Fouquet, Y., Bachèlery, P., Bermell, S., Besson, F., Bickert, M., Gaillot, A., Guérin, C., Le Friant, A., Paquet, F., Pierre, D., and Pitel-Roudaut, M.: Early development of a deep sea volcano offshore Mayotte revealed by seafloor mapping : first results from the MAYOBS cruises, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11026,, 2020.