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The Atlantic Ocean may soon enter its declining phase

A new study utilizing advanced computational models has made a startling prediction about the future of the Atlantic Ocean. 

Researchers suggest that a subduction zone located beneath the Gibraltar Strait is set to extend further into the Atlantic, potentially giving rise to an Atlantic Ring of Fire, akin to the Pacific’s notorious volcanic and seismic belt. 

This significant geological shift is expected to occur ‘soon’ on a geological scale, approximately 20 million years from now.

The Wilson Cycle 

The concept of oceans as permanent fixtures on Earth’s surface is challenged by the reality of the Wilson Cycle, which describes the birth, growth, and eventual closure of oceanic bodies over hundreds of millions of years. 

The Atlantic Ocean itself, formed from the breakup of the supercontinent Pangea around 180 million years ago, is destined to follow this cycle and eventually close. The Mediterranean Sea stands as a remnant of the once vast Tethys Ocean that lay between Africa and Eurasia.

Subduction invasion 

For the Atlantic to transition from expansion to closure, new subduction zones, where one tectonic plate dives beneath another, must emerge. However, the formation of subduction zones is a complex process due to the immense strength of tectonic plates. 

A potential resolution to this “paradox” is the migration of subduction zones from older, contracting oceans, like the Mediterranean, to younger basins, such as the Atlantic – a process termed “subduction invasion.”

Study significance 

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. This transformative event is predicted to unfold in roughly 20 million years.

João Duarte, the study’s lead author from the Instituto Dom Luiz at the University of Lisbon‘s Faculty of Sciences (Ciências ULisboa), Portugal, highlights 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.”

Critical insights 

The study also re-evaluates the activity of the Gibraltar subduction zone, which some researchers previously thought was dormant due to a slowdown in activity over the last million years. The findings suggest this lull will persist for another 20 million years before the zone invades the Atlantic and intensifies, marking the onset of crustal recycling on the Atlantic’s eastern flank and potentially the beginning of the ocean’s closure.

Duarte further explains the significance of studying the Gibraltar zone: “There are two other subduction zones on the other side of the Atlantic – the Lesser Antilles, in the Caribbean, and the Scotia Arc, near Antarctica. However, these subduction zones invaded the Atlantic several million years ago. Studying Gibraltar is an invaluable opportunity because it allows observing the process in its early stages when it is just happening.”

Study implications 

This research posits subduction invasion as a likely mechanism for initiating subduction in Atlantic-type oceans, underscoring its importance in Earth’s geological evolution. 

Moreover, the confirmation of ongoing activity in the Gibraltar subduction zone carries implications for seismic risk in the region, emphasizing the need for preparedness against potentially devastating earthquakes, reminiscent of the 1755 Great Lisbon Earthquake.

The study is published in the journal Geology.

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