Geologists may have traced the source of last year’s unexplained massive Earth shake

Location of Mayotte, in the Indian Ocean off the coast of Southeast Africa

Epic.

Last November, a huge seismic event that shook the planet left experts wondering about its possible source, says ScienceAlert.

Researchers now think they know what might have caused it: an offshore volcanic event unlike any other in recorded history.

If the hypothesis is right, and there has been a massive movement of magma underneath the sea floor, that has implications for nearby Mayotte and the neighbouring Comoros islands off the coast of Africa.

Mayotte has already started to sink (by around 9 mm or 0.35 inches per month) and move eastward (by around 16 mm or 0.63 inches per month) – movements that would tally with an underground chamber getting deflated as magma flows out.

“We believe that the 2018 crisis is associated to an eruption, despite the fact that we do not have direct observations so far,” write the researchers behind the new study.

“It might be the offshore eruption with the largest volume ever documented.”

Based on the seismic readings taken in the area over six months leading up to the November tremor that was spread across the world, the team suggests more than a cubic kilometre (0.24 cubic miles) of magma has been shifted from an eruption point some 28 kilometres (17.4 miles) below the surface.

The thinking is that all this magma may not have reached the seafloor but instead flowed into the surrounding sediments, with volcanic gas remaining trapped inside the magma. That would explain why nothing has been observed yet above the surface.

“The 2018 event at Mayotte does appear to show a substantial volume of magma leaving a deep storage region which, if erupted, would make this indeed one of the largest recent submarine eruptions documented,” geologist Samuel Mitchell from the University of Hawaii at Mānoa, who wasn’t involved in the study, told Gizmodo.

As the tremors continue, scientists are scrambling to get more instruments and equipment to the area, to get a better idea of what’s actually going on. For the time being, the idea of a major volcanic event fits the existing data pretty well.

There are still lots of unanswered questions though…

Continued here.

View paper (pre-print) here.