A seismic storm could be brewing beneath the Atlantic Ocean, with a new tectonic fault on the rise, potentially escalating the threat of powerful earthquakes and tsunamis that might shake coastlines across the basin. This alarming discovery was unveiled in a recent study published in *Nature Geoscience*.

For centuries, the mystery of why Portugal experiences devastating earthquakes—despite its distance from the planet’s significant fault lines—has puzzled scientists. Historically, on November 1, 1755, Lisbon was rocked by a massive 8.7 magnitude quake, leading to tens of thousands of deaths and tsunami waves that travelled as far as the Caribbean.

Then, in 1969, another deadly tremor of 7.8 magnitude struck off the Portuguese coast, claiming 25 lives. Prof. João Duarte, a leading geologist from the University of Lisbon and the study's lead author, remarked, 'After the 1969 earthquake, people started to realize that something strange was going on. It had the signature of a subduction zone, yet there isn't one here.'

Subduction zones—where one tectonic plate slots beneath another—are known for producing the most catastrophic 'megathrust' earthquakes, such as the 2004 Indian Ocean and the 2011 Tōhoku disasters. In contrast, the Atlantic has typically been seen as a placid ocean, with tectonic plates slowly drifting apart along a mid-ocean ridge.

Duarte and his team analyzed seismic records and created computer models of the Horseshoe Abyssal Plain, located southwest of Portugal. Their research revealed that the mantle—the superheated, dense layer beneath Earth’s crust—is undergoing a remarkable process called delamination.

'It’s as if the base of the tectonic plate is peeling away like the sole of a shoe,' Duarte explained. 'This was the first Eureka moment, signaling that something significant was happening beneath the surface.' The computer models supported this revelation, showcasing the delamination in action.

Unusual and rare in the oceanic crust, this 'unpeeling' is triggered by water seeping into the rock over millions of years, chemically weakening it and prompting sections of the mantle to plunge deeper into the Earth.

The study hints we might be witnessing the formation of a new subduction zone in the Atlantic—a geological shift that could eventually pull together Africa, Europe, and the Americas into a colossal future supercontinent.

However, the most pressing concern lies in the seismic hazard posed by these developments. Duarte warns, 'Big earthquakes are bound to happen again.' The potential impacts could be catastrophic for unprepared coastal regions across the Atlantic.

He emphasized the importance of readiness: 'If you’re forecasted for rain tomorrow, you grab an umbrella. You may not know precisely when the rain will start, but you prepare for it. The same rule applies to earthquakes; they may strike without warning, but we know they will happen, so preparations must commence now.'