Dear colleagues and friends,
As we now know, seas and continents have been in motion throughout Earth's life: they constantly disappear and appear in new sizes and shapes. An esteemed colleague shares with us today an article describing what will surely happen to the Atlantic Ocean in a few million years. This article was published on February 15, 2024 by the University of Lisbon, re-published on the same date by PHYS.ORG and translated by us for this space. Let's see what they tell us about it...
A new study, using computer models, predicts that a subduction zone currently below the Strait of Gibraltar will spread further into the Atlantic and will help form an Atlantic subduction system: an Atlantic ring of fire. A ring of fire is a place where the most important subduction zones in the world are concentrated, causing intense seismic and volcanic activity in the territory it covers). This will happen “soon” in geological terms: approximately 20 million years from now.
The oceans seem eternal during our lifetime, but they are not here for long: they are born, they grow and one day they close. This process, which lasts a few hundred million years, is called the Wilson cycle. The Atlantic, for example, was born when Pangea broke up about 180 million years ago and will one day close. And the Mediterranean is what's left of a great ocean, the Tethys, that once existed between Africa and Eurasia.
For an ocean like the Atlantic to stop growing and begin to close, new subduction zones (places where one tectonic plate sinks under another) have to form. But subduction zones are difficult to form, since they require plates to break and bend, and the plates are very strong. A way out of this “paradox” is to consider that subduction zones can migrate from a dying ocean in which they already exist (the Mediterranean) to pristine oceans (such as the Atlantic). This process was called subduction invasion.
This study shows for the first time how such a direct invasion can occur. The 3D computational model driven by gravity predicts that a subduction zone currently under the Strait of Gibraltar will spread further into the Atlantic and will contribute to forming an Atlantic subduction system: an Atlantic ring of fire, in analogy with the structure already existing in the Pacific. This will happen “soon” in geological terms, but not before about 20 million years.
“Subduction invasion is inherently a three-dimensional process that requires advanced modeling tools and supercomputers that weren't available a few years ago. Now we can simulate the formation of the Arc of Gibraltar in great detail and also how it may evolve in the deep future.” explains João Duarte, first author and researcher at the Dom Luiz Institute, of the Faculty of Sciences of the University of Lisbon.
This study sheds new light on Gibraltar's subduction zone, as few authors considered that it was still active because it had slowed down significantly in the last million years. According to these results, its slow phase will last another 20 million years and then it will invade the Atlantic Ocean and accelerate. That will be the beginning of crust recycling on the eastern side of the Atlantic and could be the beginning of the Atlantic itself beginning to close.
“There are two other subduction zones on the other side of the Atlantic: the Lesser Antilles, in the Caribbean, and the Arc of Scotland, near Antarctica. However, these subduction zones invaded the Atlantic several million years ago. Studying Gibraltar is an invaluable opportunity because it allows us to observe the process in its early stages, when it is just happening,” adds João Duarte.
In general terms, this study shows that invasion by subduction is probably a common mechanism for initiating subduction in Atlantic-type oceans and, therefore, plays a fundamental role in the geological evolution of our planet.
The finding that the Gibraltar subduction is currently still active also has important implications for seismic activity in the area. Subduction zones are known to produce the strongest earthquakes on Earth. Events such as the Great Lisbon Earthquake of 1755 are a unique opportunity for analysis and require a lot of in-depth study.
The work is published in the The Journal of Geology.
