Can you hear it? That elemental thrumming emerging just beneath the engulfing din of everyday city and suburban life? Well, chances are you're not losing your mind or developing some extrahuman ability akin to comic book superheroes. Better odds are that it's Mother Earth's growing pains in the form of loud volcanic stirrings, as revealed in a new study published in the journal Nature Geoscience.
First reported back in the '70s, these unexplained low-frequency rumbles were heard around the world, and though myriad theories were presented, there was no specific cause ever found, other than possible sound sources like area cooling towers, transformer substations, industrial air compressors, and even secret submarine tracking stations (as portrayed in a 1998 The X-Files episode titled Drive).
Now a German scientific team has apparently solved the mystery of a strange seismic humming experienced around the globe since it was first detected in late 2018. And despite many believing it was some alien doomsday device warming up to unleash its planet-killing spores, it appears to be caused by a massive underwater volcano forming just off the coast of Madagascar.
Beginning in the spring of 2018, a wave of intense earthquakes was recorded off the coast of the minuscule island of Mayotte, a French territory midway between Madagascar and Mozambique.
This anomaly led study co-author Simone Cesca, a German seismologist of the GFZ German Research Center for Geosciences, to conclude with his colleagues that they were caused by an enormous pocket of molten magma slowly draining up to meet the sea floor of the Indian Ocean. According to their latest research paper, it’s the largest magma chamber ever discovered, and measures in at a whopping 16 to 19 miles deep.
While surrounding rock filtered and sagged down over the draining magma lake, the ocean floor responded by emitting an epic hum starting in June 2018, and first heard five months later. This gradual draining process also gave birth to a ginormous undersea volcano that spanned three miles in diameter and rose to a height of nearly 2,500 feet.
The primal machinations creating the underwater volcano began voicing a faint seismic humming that wasn't heard until Nov. 11, 2018, when sonic waves traversed the Earth from Kenya to Chile and Canada to the Hawaiian Islands, growing louder and lasting up to 30 minutes at a time. This thunderous downsag of the host rock overlying the reservoir is what triggered the worldwide resonance by emitting 407 very-long-period seismic signals.
“The whole episode is really, really rare,” Cesca told The Washington Post. “Seeing the deep magma chamber, seeing the magma’s propagation to the surface, seeing the volcano being born — I think this is unique, absolutely. Every time the rock sags into the chamber, it creates a resonance and this produces this strange signal that you see far away.”
So next time your ears pick up some odd reverberations you can't quite identify, it just might be the birthings of some baby volcano arriving into the world.