Portugal has a history of powerful earthquakes, a fact that has long baffled scientists because it's not near any known fault lines. A new study, however, may finally provide the answer: Researchers found a fissure in the tectonic plate on the ocean floor about 120 miles off the coast, reports EuroNews. "The base of the plate is separating like the sole of a shoe peeling off," University of Lisbon geologist Joao Duarte tells the BBC. "That was the first Eureka moment when I thought, 'Aha, there's something there.'" Duarte is the lead author of the new study in Nature Geosciences.
The study points to a rare process called oceanic plate delamination beneath the Horseshoe Abyssal Plain, off the Iberian Peninsula's coast, per a release. Using seismic imaging and ocean-bottom sensors, researchers identified a block of old oceanic lithosphere that's breaking apart, with its lower section sinking into Earth's mantle. While delamination has been observed in continental plates, this is the first time it's been detected in an oceanic plate.
The study suggests that water infiltrating the oceanic crust—a process known as "serpentinization"—transforms the rock, making it easier for the plate to split and for the bottom half to drop away. The BBC adds a note of jaw-dropping perspective:
- "The findings suggest we may be witnessing the birth of a new subduction zone in the Atlantic—one that could eventually pull Africa, Europe and the Americas back together into a future supercontinent."
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