A New Seamount

[Recusant]

It's a respectable size, and still growing. It also is apparently the source of a low-frequency hum/rumble that was "heard" all over the world a few years ago.

Image credit: James Tuttle Keane/Nature Geoscience 2020

"Largest Underwater Eruption Ever Recorded Gives Birth to Massive New Volcano" | Science Alert

Elevation maps in 2014 and 2019 reveal the new volcano.
Image credit: Feuillet et al., Nature Geoscience, 2021

A huge seismic event that started in May of 2018 and was felt across the entire globe has officially given birth to a new underwater volcano.

Off the eastern coast of the island of Mayotte, a gigantic new feature rises 820 meters (2,690 feet) from the seafloor, a prominence that hadn't been there prior to an earthquake that rocked the island in May 2018.

"This is the largest active submarine eruption ever documented," the researchers wrote in their paper.

The new feature, thought to be part of a tectonic structure between the East African and Madagascar rifts, is helping scientists understand deep Earth processes about which we know relatively little.

The seismic rumbles of the ongoing event started on 10 May 2018. Just a few days later, on 15 May, a magnitude 5.8 quake struck, rocking the nearby island. Initially, scientists were perplexed; but it didn't take long to figure out that a volcanic event had occurred, the likes of which had never been seen before.

The signals pointed to a location around 50 kilometers from the Eastern coast of Mayotte, a French territory and part of the volcanic Comoros archipelago sandwiched between the Eastern coast of Africa and the Northern tip of Madagascar.

So a number of French governmental institutions sent a research team to check it out; there, sure enough, was an undersea mountain that hadn't been there before.

Led by geophysicist Nathalie Feuillet of the University of Paris in France, the scientists have now described their findings in a new paper.

[Continues . . .]

The paper is behind a paywall, unfortunately.

Abstract:

Volcanic eruptions shape Earth's surface and provide a window into deep Earth processes. How the primary asthenospheric melts form, pond and ascend through the lithosphere is, however, still poorly understood.

Since 10 May 2018, magmatic activity has occurred offshore eastern Mayotte (North Mozambique channel), associated with large surface displacements, very-low-frequency earthquakes and exceptionally deep earthquake swarms. Here we present geophysical and marine data from the MAYOBS1 cruise, which reveal that by May 2019, this activity formed an 820-m-tall, ~5 km³ volcanic edifice on the seafloor.

This is the largest active submarine eruption ever documented. Seismic and deformation data indicate that deep (>55 km depth) magma reservoirs were rapidly drained through dykes that intruded the entire lithosphere and that pre-existing subvertical faults in the mantle were reactivated beneath an ancient caldera structure. We locate the new volcanic edifice at the tip of a 50-km-long ridge composed of many other recent edifices and lava flows. This volcanic ridge is an extensional feature inside a wide transtensional boundary that transfers strain between the East African and Madagascar rifts. We propose that the massive eruption originated from hot asthenosphere at the base of a thick, old, damaged lithosphere.

[¶ added. - R]

[Tank]

Wow! 

[Ecurb Noselrub]

Somebody is probably already planning a resort there - either underwater or after it breaches the surface, if it ever does.

[Dark Lightning]

That's wild- over half a mile high! Not like Hawai'i, but still, it could get there, in say, 10k years.