On May 10, 2018, seismic rumbles began between the rifts in East Africa and Madagascar, culminating in a magnitude 5.8 earthquake five days later.
Shortly after, researchers learned that a volcanic event had occurred 50 kilometers off the east coast of the French territory of Mayotte, located between the east coast of Africa and northern Madagascar.
A search team investigated a few months later – and they found a new volcano, one that wasn’t there before the earthquake.
“It is the largest active underwater eruption ever documented”, the paper says – and the seismic activity is at the origin of the new mountain, which rises 820 meters from the seabed.
The new feature will help scientists better understand what is happening deep in the earth.
The mountains are not the only thing the France team has discovered. When they started their survey in early 2019, several seismometers and sonar were used to take measurements. Between February 25 and May 6, 2019, 17,000 seismic events ranging from 20 to 50 km below the seabed were recorded. This is unusual, the researchers say, because most earthquakes are shallower than that.
The data helped scientists paint a picture of how the new volcano might have been born. The results suggest that a magma reservoir in the asthenosphere was drained through the crust after tectonic processes damaged the layer above the asthenosphere, called the lithosphere.
A 3D view looking west of the underwater volcanic formations east of Mayotte. (Feuillet et al./Geosciences of nature
This event probably caused “swarms” of earthquakes.
As of May 2019, the volume of the new volcanic feature was between 30 and 1,000 times greater than what is believed to be in other deep-water eruptions.
The results are detailed in a new paper published in the journal Natural geosciences.