Although it may seem like an eternal feature of Earth, the Atlantic Ocean could be engulfed by a vast subduction zone, nicknamed the “Ring of Fire,” a new study warns.
Portuguese scientists say this subduction zone is currently located beneath the Strait of Gibraltar, the narrow gap between Spain and Morocco.
But experts believe it could grow and expand westward into the Atlantic and eventually become responsible for a “closure” or shrinking of the ocean basin.
This will happen “soon” in geological terms – in about 20 million years – at a time when humans may still be alive on the planet.
Subduction zones are places on Earth where one tectonic plate dips beneath another and are known for their powerful seismic activity.
It is well known that Earth’s lithosphere (its outermost rocky shell) is made up of approximately 15 tectonic plates, each of different shapes and sizes. Powerful seismic activity can be detected along tectonic plate boundaries, where plates rub against each other. This diagram shows tectonic plate boundaries with newly formed crust in red.
The Strait of Gibraltar lies between the countries of Spain (to the north) and Morocco (to the south). This 16-kilometer strait which separates the two countries (as well as Europe and Africa) is the collision point of two major tectonic plates (the Eurasian plate and the African plate).
The new study was led by João Duarte, professor of tectonics at the Faculty of Science at the University of Lisbon, Portugal.
He and his colleagues warn that entire oceans can close if new “subduction zones” form – and this process may have already started with the Atlantic.
‘We have good reason to believe that the Atlantic is starting to close,’ Professor Duarte told MailOnline.
“Subduction zones are the cause of the closure of the oceans, by bringing their sea floors back into the mantle, thus bringing the continents closer together.”
The 16 km long Strait of Gibraltar, which separates Spain and Morocco (as well as Europe and Africa), is the meeting point of two major tectonic plates: the Eurasian plate and the African plate.
In this subduction zone, the African plate sinks beneath the Eurasian plate, leading to 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 through the Earth’s mantle is “very, very slow.”
Professor Duarte and his colleagues say subduction zones can expand into another part of the ocean – a process called “subduction invasion”.
In subduction zones, Earth’s tectonic plates converge and one plate sinks beneath another (photo)
Map highlighting the Atlantic subduction zones, the fully developed Lesser Antilles and Scotia arcs on the west side and the Gibraltar arc on the east side
Currently, the subduction zone beneath the Strait of Gibraltar is approximately 125 miles long (although it dips to a depth of over 350 miles), making it one of the smallest subduction zones in the world. world.
But in 20 million years it could reach a length of about 500 miles, Professor Duarte said.
For the study, the team used computer modeling to simulate the life of the subduction zone since its birth in the Oligocene epoch (34 million to 23 million years ago).
By modeling its fate into the future, they found that it would move westward across the narrow Strait of Gibraltar over the next 20 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 version already existing in the Pacific Ocean.
Subduction slowly pulls the ocean floor down, bringing the continents closer together as the ocean basin shrinks.
Therefore, this new Ring of Fire could “close” the Atlantic, causing it to cease to exist – but in about 20 million years.
“The results suggest that the arc will propagate further into the Atlantic after a period of rest,” says the team in their study published in the journal Geology.
Maps showing the evolution of the Gibraltar subduction zone from 30 million years ago to 50 million years in the future
“The models also show how a subduction zone starting in a closing ocean can migrate to a new opening ocean through a narrow ocean 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 the Earth.”
The discovery that Gibraltar subduction is still active also has important implications for seismic activity in the region.
Events such as the Great Lisbon Earthquake of 1755 are reminders of the existing seismic threat and require “preparation”.
This historic event – with an estimated magnitude of 7.7 – killed around 12,000 people and almost completely destroyed Lisbon and its surrounding areas.
The Earth moves beneath our feet: tectonic plates move through the mantle and produce earthquakes when they rub against each other.
Tectonic plates are made up of the Earth’s crust and the upper part of the mantle.
Below is the asthenosphere: the hot, viscous conveyor belt of rock on which tectonic plates sit.
The Earth is made up of fifteen tectonic plates (pictured) which together have shaped the shape of the landscape we see around us today.
Earthquakes typically occur at tectonic plate boundaries, where one plate dips below another, pushes another up, or where plate edges rub against each other.
Earthquakes rarely occur in the middle of plates, but they can occur when old faults or faults well below the surface reactivate.
These areas are relatively weak compared to the surrounding plate and can easily slide and cause an earthquake.