What Is Happening Off Of Mayotte Island?

A small French territory island between Africa and Madagascar is making some big news. For several months, the volcanic island of Mayotte, in the Comoros Islands (which has not had a confirmed surface eruption since 2050 BCE) is getting very noisy. So noisy in fact that the earthquakes and seismic noise it is generating has been detected worldwide. And now, scientists say this could be the result of the largest ever underwater eruption in modern history.

Mayotte Island is a volcano, however it has had no eruptive activity in historical times. Offshore however, scientists are detecting very unusual activity, and large earthquakes (a 5.0 temblor struck today following months of other strong quakes), which have generated a 'huge rumble heard all around the world'. A 5.9 magnitude quake struck on May 15, 2018, and since then, the activity has continued. The seafloor off the coast of the island is sinking at a rate of about 0.4 inches per month as well.

This has been interpreted by geologists to mean that there is a large movement of magma, and possible offshore eruption - the largest ever recorded. Due to the depths and pressure, it is unclear whether the magma has broken through the sedimentary layer, or generated a new seamount, but given the length of the activity and amount of magma involved, it is quite possible. No underwater observations have yet occurred, so this is impossible to know at the moment.

Image from the March 12, 2019 scientific publication showing three distinct seismic crisis offshore of Mayotte.

According to the summary of a detailed study published at EarthArXiv, "We believe that the 2018 crisis is associated to an eruption, despite the fact that we do not have direct observations so far. It might be the offshore eruption with the largest volume ever documented."

As for the safety of the island of Mayotte, "If the eruption lasts one year, which is typical for volcanic eruption, the subsidence of Mayotte will exceed 0.1 m which is large but not critical for the inhabitants and infrastructures, and the total volume emitted will exceed 2 (square kilometers). Such volcanic event (sic) near the coast is the largest ever observed and it may be a major teacher for the understanding of how off-shore volcanoes work."

As of today, the activity continues with a 5.0 magnitude quake. Several other large (4.0+) quakes have occurred within the week. USGS does not have instrumentation to show the smaller quakes, but local geologists are monitoring the situation intensely. 

Google Earth capture with my volcano database and USGS plugin showing the location of the last large 5.0 earthquake.

At present, there is no danger to life or property, and the island is safe. With more instruments being deployed worldwide, and with the continuing discovery of underwater volcanoes and their activities, it is likely that we'll be detecting more and more underwater eruptions with better accuracy as time goes on.

This particular eruption however, will fascinate for a long time.