Why the Atlantic Ocean may ultimately vanish

A groundbreaking study led by the University of Lisbon raises the startling possibility that the Atlantic Ocean might one day vanish, consumed by an expanding subduction zone known as the “Ring of Fire.”

According to the research, currently nestled beneath the Strait of Gibraltar – the sliver of sea separating Spain from Morocco – this subduction zone could extend westward into the Atlantic, potentially initiating the ocean basin’s gradual closure. 

Process may already be underway 

This significant geological shift is predicted to occur “soon” in geological terms, roughly in 20 million years, suggesting that humanity might witness this monumental change.

Subduction zones, where one tectonic plate is forced beneath another, are hotspots for intense seismic events. Led by Professor João Duarte at the University of Lisbon’s Faculty of Sciences, the study emphasizes that the formation of new subduction zones could herald the eventual disappearance of entire oceans, a process that might already be underway with the Atlantic. 

“We have good reason to think that the Atlantic is starting to close,” Duarte said. “Subduction zones are what cause the oceans to close, by pulling their ocean floor back into the mantle, bringing the continents together.”

Potential for subduction invasion 

The Strait of Gibraltar, which is just 10 miles wide, marks the junction of the Eurasian and African Plates. Within this subduction zone, the African plate is diving beneath the Eurasian plate, stirring seismic activity and heightening earthquake risks. 

Presently, the subduction zone’s activity is described as “sleeping,” with plate movement into the Earth’s mantle occurring at a notably sluggish pace. However, Duarte and his team speculate that subduction zones have the potential to expand, a phenomenon they term “subduction invasion.”

Atlantic Ocean could vanish gradually

Though the Gibraltar subduction zone currently spans about 125 miles in length and reaches depths exceeding 350 miles, it’s among the smallest globally. Yet, Duarte suggests it could stretch to approximately 500 miles in 20 million years. 

Through computer simulations tracing the subduction zone’s development from the Oligocene epoch (34 million to 23 million years ago) into the future, the researchers anticipate its westward migration through the narrow Strait of Gibraltar over the coming 20 million years. 

These models forecast the emergence of a new Atlantic subduction system, akin to the Pacific Ocean’s Ring of Fire, which gradually diminishes the ocean floor and draws continents closer, potentially leading to the Atlantic’s disappearance.

Fundamental process in Earth’s evolution 

“The results suggest that the arc will propagate farther into the Atlantic after a period of quiescence,” the authors wrote. “The models also show how a subduction zone starting in a closing ocean can migrate into a new opening ocean through a narrow oceanic corridor.”

“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 discovery also underscores the active nature of the Gibraltar subduction and its implications for regional seismic hazards. The devastating 1755 Great Lisbon Earthquake, which virtually obliterated Lisbon and claimed approximately 12,000 lives, serves as a stark reminder of the area’s seismic vulnerability, necessitating ongoing preparedness efforts.

New evidence of the Atlantic subduction system 

This research marks the first illustration of such an invasion occurring directly. A sophisticated, gravity-driven 3-D model forecasts the expansion of a subduction zone beneath the Gibraltar Strait into the Atlantic, laying the groundwork for an Atlantic subduction system. 

Duarte highlighted the technological advancements enabling this discovery: “Subduction invasion is inherently a three-dimensional process that requires advanced modeling tools and supercomputers that were not available a few years ago.”

“We can now simulate the formation of the Gibraltar Arc with great detail and also how it may evolve in the deep future.”

The study is published in the journal Geology.

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