Many of the Earth's most dramatic natural phenomena are hidden from us. For example: according to a new pre-print paper, the largest offshore volcanic event in recorded history .
If you don't remember, don't worry. No human on the planet could feel the event, and many seismic machines also missed it.
At the time, November 11, 2018, scientists noted that "something big" was happening. The origin point seemed to be located near the African island nation of Madagascar and island of Mayotte, which is controlled by the French government. “What’s unusual is you see this very long signal traveling most of the way around the world which hasn’t been detected by operational earthquake detection systems,” said Stephen Hicks at the time, a seismologist at the University of Southampton speaking to .
Geologists had been paying attention to the region since May 2018, when the Madagascar-Mayotte region was hit by a 5.8 earthquake. Scientists weren't sure, but after the November event, they suspected the two were related.
While the event is still mysterious, the new paper from researchers at the French Geological Survey and France’s Ecole Normale Supérieure offers some suggestions. It appears that a vast amount of magma shifted on the ocean's floor. That shifting caused the ground below the magma, known as a magma chamber, to significantly deflate. That's what led to the invisible rumbling.
It's a solid theory that makes sense. But a major problem, as , is that there's a major lack in offshore monitoring of earthquakes. "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," says Samuel Mitchell, an expert in underwater eruptions at the University of Hawaii at Mānoa, speaking to the site. Scientists have not ruled out the chance that something else is happening deep below the ocean floor.
The event appears to still be ongoing, whatever it is, and still affecting the area around Mayotte, which has a population of around 246,000. Readings indicate that the seafloor off the French island's eastern shoreline is sinking at a rate of approximately 0.4 inches per month.
"The people in Mayotte really want to know what’s going to happen next,” says Jean Paul Ampuero, a seismologist and director of research at France’s Research Institute for Development, speaking to Gizmodo. That understandable, considering all the unknowns still at play:, like what's causing the volcanic activity. There are also curious and unsubstantiated reports of deep-sea fish burning up in the magma shift.