The eruption off the island of Mayotte was not interrupted during the crisis due to the coronavirus… This is what scientists observed during a double campaign organized under original conditions, in full containment . The purpose of the mission was to go and examine the underwater volcano discovered last year, some 50 km east of the archipelago, and to deploy instruments at sea to monitor it. Researchers conclude: While less active, the site has undergone significant changes since the last time it was observed, in August 2019. An additional lava flow appeared. The morphology of the seabed was therefore changed, with the emergence of a new structure several hundred meters high. And, in the coastal area, the number of plumes has increased.
The launch of this campaign was a real headache. This was to take place at the end of April on board the Marion-Dufresne. However, the French Southern and Antarctic Territories (TAAF) ship has postponed the date of its operation to supply the Crozet and Kerguelen archipelagos and the Saint Paul and Amsterdam islands because of the new health protocols to be observed since the start of confinement, its organizers had to hastily search for another building. And this at the very moment when, owing to the pandemic, orders had been given to the entire French oceanographic fleet to join its home ports and stay at the quay. The solution finally found consisted in using two boats: the Champlain of the national navy, based in Reunion, and the Gauss, of the Fugro company, which left Egypt two weeks earlier and had no sick on board, was en route to South Africa.
An unprecedented phenomenon
It must be said that scientists could not afford the luxury of waiting, at the risk of compromising the mission they were given by the State in the department of Mayotte. Since May 2018, the latter has experienced an unprecedented phenomenon: an unbroken succession of more than 2,000 earthquakes, of which the 35 largest, of a magnitude greater than 5, have worried the population. Added to this is a displacement of the archipelago which, in the space of two years, migrated from 20 to 23 cm east and collapsed from 9 to 17 cm.
This eruption is “one of the few to have been observed in the underwater environment”
The explanation? The start of a great volcanic eruption. This led to the formation, by 3,500 meters deep, off the island, of a volcano whose existence was not discovered until May 2019. It measures 800 meters in height, did not exist not a year ago and would have already produced more than 5 km3 of magma, which would make this the strongest basaltic eruption in the world since that of Laki, Iceland, in 1783-1784. But also, specifies Nathalie Feuillet, of the Paris Institute of Physics of the Globe (IPGP), “One of the few to have been observed in the underwater environment”.
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