The Atlantic Ocean could be swallowed by a terrifying ‘ring of fire’, scientists say as they discover ‘dormant’ subduction zone beneath the Strait of Gibraltar
While it may seem like an eternal feature of Earth, the Atlantic Ocean could be swallowed up by a massive subduction zone called the ‘Ring of Fire’, a new study warns.
Scientists in Portugal say this subduction zone is currently located beneath the Strait of Gibraltar, the narrow gap of water between Spain and Morocco.
But experts think it could grow and expand westward into the Atlantic Ocean and eventually become responsible for a “closing” or contraction of the ocean basin.
This will happen ‘soon’ in geological terms – in about 20 million years – at a time when humans could still be living on the planet.
Subduction zones are locations on Earth where one tectonic plate subducts beneath another and are known for their powerful seismic activity.
Earth’s lithosphere (the rocky, outer shell) is known to consist of about fifteen tectonic plates, each with different shapes and sizes. Strong seismic activity can be detected along tectonic plate boundaries, where the plates grind against each other. This diagram shows tectonic plate boundaries with newly formed crust in red
The Strait of Gibraltar is located between the countries of Spain (north) and Morocco (south). In this 16 kilometer long strait that separates the two countries (as well as Europe and Africa), two major tectonic plates (the Eurasian plate and the African plate) collide.
The new study is led by João Duarte, professor of tectonics at the Faculty of Science of the University of Lisbon, Portugal.
He and his colleagues warn that entire oceans could close as new ‘subduction zones’ form – and this process may have already begun with the Atlantic Ocean.
“We have good reason to think that the Atlantic Ocean is starting to close,” Professor Duarte told MailOnline.
‘Subduction zones cause the oceans to close by pulling their ocean floor back into the mantle, bringing the continents together.’
In the 16 kilometer long Strait of Gibraltar that separates Spain and Morocco (as well as Europe and Africa), two major tectonic plates meet: the Eurasian plate and the African plate.
In this subduction zone, the African plate subducts beneath the Eurasian plate, resulting in seismic activity and the risk of earthquakes.
Currently, the subduction zone beneath the Strait of Gibraltar is ‘dormant’, meaning the rate at which the plate is sliding down into the Earth’s mantle is ‘very, very slow’.
Professor Duarte and colleagues say subduction zones can grow to invade another part of the ocean – a process called ‘subduction invasion’.
In subduction zones, Earth’s tectonic plates converge and one plate sinks beneath the other (photo)
Map highlighting the Atlantic subduction zones, the fully developed Lesser Antilles and Scotia arcs on the western side and the Gibraltar arc on the eastern side
Currently, the subduction zone beneath the Strait of Gibraltar is about 200 kilometers long (although it plunges to a depth of more than 550 kilometers), making it one of the smallest subduction zones in the world.
But in 20 million years it could reach a length of about 800 kilometers, Professor Duarte said.
For the study, the team used computer models to simulate life in the subduction zone since its birth during the Oligocene (34 million to 23 million years ago).
By modeling its fate in the future, they found that it will move westward through the narrow Strait of Gibraltar over the next twenty million years.
The model predicts that the extended subduction zone will form a new Atlantic subduction system – the so-called ‘Ring of Fire’, named after the pre-existing version of the Pacific Ocean.
Subduction slowly pulls the ocean floor underwater, dragging the continents closer together as the ocean basin shrinks.
Therefore, this new Ring of Fire could ‘close off’ the Atlantic Ocean, causing it to cease to exist – albeit in an estimated 20 million years.
“The results suggest that the arc will spread further into the Atlantic Ocean after a period of quiescence,” the team said in their study, published in the journal Geology.
Maps showing the evolution of Gibraltar’s subduction zone from 30 million years ago to 50 million years into the future
‘The models also show how a subduction zone that starts in a closing ocean can migrate through a narrow oceanic corridor to a new opening ocean.
‘Subduction invasion is likely a common mechanism of subduction initiation in Atlantic-type oceans and a fundamental process in Earth’s recent geological evolution.’
The finding that Gibraltar subduction is currently still active also has important implications for seismic activity in the area.
Events such as the Great Lisbon Earthquake of 1755 are reminders of the existing seismic threat and require ‘preparedness’.
The historic event – with an estimated magnitude of 7.7 – killed around 12,000 people and almost completely destroyed Lisbon and neighboring areas.
The Earth moves beneath our feet: Tectonic plates move through the mantle, causing earthquakes as they scrape against each other
Tectonic plates consist of the Earth’s crust and the upper part of the mantle.
Below this is the asthenosphere: the warm, viscous conveyor belt of rock on which tectonic plates ride.
The Earth has fifteen tectonic plates (pictured) that together form the shape of the landscape we see around us today
Earthquakes typically occur at tectonic plate boundaries, where one plate subducts under another, pushes the other up, or where plate edges rub against each other.
Earthquakes rarely occur at the center of plates, but can occur when ancient faults or fissures far below the surface are reactivated.
These areas are relatively weak compared to the surrounding plate and can easily slip and cause an earthquake.