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Rabat – A new scientific study from the Geological Society of America (GSA) suggests that a dramatic change may be in store for the Atlantic Ocean; the potential birth of a new subduction zone near the Strait of Gibraltar between Spain and Morocco.
This finding challenges the prevailing idea that the Atlantic is passive and immune to the forces that drive the “ring of fire” around the Pacific.
Subduction zones are pivotal features that drive plate tectonics on Earth. They occur at convergent plate boundaries, where two plates collide and one is forced underneath the other into the mantle. This process recycles oceanic crust and is responsible for building mountains, triggering earthquakes, and forming volcanic arcs.
The study, published in GSA’s Journal Geology, uses advanced computer models to investigate whether the existing Gibraltar subduction zone could propagate eastward from the Mediterranean into the Atlantic.
Researchers explained, “Subduction initiation is a cornerstone of the Wilson cycle. It marks the turning point in an ocean’s lifetime, allowing its lithosphere to be recycled into the mantle.”
The Atlantic already hosts two subduction zones – the Lesser Antilles and the Scotia arc – forced by the proximity of the Pacific plate’s subduction zones.
The Mediterranean region has also spawned its own subduction system, starting over 10 million years ago when Africa and Europe began converging. This led to the closure of the Ligurian Ocean basin between Corsica and Sardinia.
Normally, forming a new subduction zone in the middle of an ocean is difficult without an external force. But the Gibraltar subduction zone originally developed in the Mediterranean before the seaway between the Atlantic and Mediterranean opened.
New computer models from GSA suggest that after a period of quiescence, this Gibraltar subduction zone could reactivate and continue marching eastward into the Atlantic.
If the model proves correct, the Atlantic seafloor would start plunging beneath the African continental crust, pulling Africa and Europe closer together.
Researchers elaborated, “Subduction invasion is likely a common mechanism of subduction initiation in Atlantic-type oceans and a fundamental process in the recent geological evolution of Earth.”
This potential birth of a new subduction zone is tied to the complex geologic history of the Mediterranean region.
Over millions of years, the slow collision between the African and Eurasian tectonic plates led to the closure of the ancient Tethys Ocean. Its last remnant is the Mediterranean Sea, which continues to shrink as Africa pushes northward into Europe.
Around this contracting Mediterranean, smaller ocean basins like the Ligurian Sea have been eliminated altogether through subduction. As the researchers put it, “The Gibraltar arc is another place where a subduction zone is invading the Atlantic. This corresponds to a direct migration of a subduction zone that developed in the closing Mediterranean Basin.”
Based on seismic imaging and the volcanism of the Atlas Mountains, geologists deduce that some subduction is still happening today at Gibraltar.
However, because the rate of sinking has slowed over the last several million years, many scientists have concluded that Gibraltar subduction was no longer active. But the new computer models account for this lull and predict a reactivation in the future.
The GSA researchers concluded, “The models show how a subduction zone starting in a closing ocean can migrate into a new opening ocean through a narrow oceanic corridor.”
The Atlantic may not remain passive after all. The Gibraltar subduction zone is poised to awaken from its multi-million year slumber and pave the way for the Atlantic seafloor to start plunging into Earth’s mantle – rewriting the fate of the ocean.
