The new underwater volcano reaches 820 meters above the seabed where nothing existed before. The volcanic island appeared suddenly in 2018 and stretches from the seabed to the east of the island of Mayotte, between East Africa and Madagascar.
It did not exist before 2018
The seismic event that gave rise to the new volcano began on May 10, 2018 and in a few days an earthquake of magnitude 5.8 on the Richter scale occurred. It shook nearby islands, and it didn’t take long for scientists to realize that it had been the result of a new volcanic event under the ocean. The signs pointed to a location about 50 kilometers off the eastern coast of Mayotte. For this reason, a group of French government institutions, led by researcher Nathalie Feuillet from the University of Paris (France), organized an expedition to French African territory. And there it was. Where there was nothing before, an underwater mountain rose that would have required a large number of cubic meters of lava to form said volcano.
“This is the largest active underwater eruption ever documented,” the researchers wrote in their paper published in the journal Nature Geoscience.
This new seamount, believed to be part of a tectonic structure between the East African rift and Madagascar, is helping scientists understand deep processes on Earth that we know relatively little about.
The formation of the volcano
The experts studied the seismic activity, collecting data on the deformation of the surface, a sonar to map an area of 8,600 square kilometers on the seabed or a network of seismometers also on the seabed, among other things, discovering that the new volcano submarine is at the end of a series of recent lava flows. The geologic feature is likely part of an extensional tectonic structure formed by fissures and faults associated with the East African Rift to the west.
The seismometer network detected a total of 17,000 seismic events between February and May 2019 from a depth of up to 50 kilometers below the ocean floor , something ‘very unusual’. Most earthquakes are much shallower than this and, to add to the confusion, another 84 events occurred at very low frequencies.
“The earthquakes have been much deeper than usual in a volcanic context and occur below the boundary between the crust and the mantle,” the scientists explain . “They point to the existence of very deep deposits and drainage systems scattered throughout the lithosphere , which have never before been clearly observed in volcanology.”
By their calculations, the new volcano is between 30 and 1,000 times larger than estimated for other deep-sea eruptions , making it the most significant undersea volcanic eruption ever recorded.
“The volumes and flow of lava emitted during the Mayotte magmatic event are comparable to those seen during eruptions at Earth’s largest hot spots,” the researchers wrote.
This means that in the future there could even be eruptions on land. Hence, an observatory has been established to monitor activity in real time.
Referencia: Feuillet, N., Jorry, S., Crawford, W.C. et al. Birth of a large volcanic edifice offshore Mayotte via lithosphere-scale dyke intrusion. Nature. Geoscience. 14, 787–795 (2021). https://doi.org/10.1038/s41561-021-00809-x
