Atlantic Ocean Might Be Widening Due to a Puzzling Phenomenon

A group of researchers deployed a fleet of undersea drones to study the phenomenon.
Chris Young
A cloudy Atlantic Ocean in MiamiMilan Boers/Flickr

Scientists estimate that the Atlantic Ocean is growing wider by several centimeters every year while the Pacific Ocean is shrinking at a similarly glacial pace.

While the scientific community knows that the shift is due to the movement of tectonic plates, it is far from fully understanding the geophysical forces behind the phenomenon, Science Alert reports.

In a bid to gain knowledge on the subject, a team from the University of Southampton sent a fleet of undersea robots to record seismic movements underneath the Mid-Atlantic Ridge. Their findings have been published in Nature.

In their study, the scientists posit that the dynamics of the Mid-Atlantic ridge — the boundary that tectonically separates the Americas from Europe and Africa  — play an important role in the widening of the Atlantic Ocean.

"Sinking slabs and rising plumes are generally accepted as locations of transfer, whereas mid-ocean ridges are not typically assumed to have a role," the team led by seismologist Matthew Agius from the University of Southampton in the UK explains in the new paper.

"However, tight constraints from in situ measurements at ridges have proved to be challenging," it continues. 

'Material transfer' from lower to upper mantle

Seismic recordings from the fleet of undersea robots, called seismometers, monitored the flow of material in the mantle transition zone between the upper and lower mantle.

This allowed the team to image material transfer at depths of up to 660 kilometers (410 miles) below the surface.

The data suggest that chemical material from the lower mantle rises upwards, something that was previously only thought to occur in the shallow depths of the Mid-Atlantic Ridge.

"The observations imply material transfer from the lower to the upper mantle – either continuous or punctuated – that is linked to the Mid-Atlantic Ridge," the researchers explain.

"Given the length and longevity of the mid-ocean ridge system, this implies that whole-mantle convection may be more prevalent than previously thought," they continue.

The new findings show that that the processes contributing to seafloor spreading extend far deeper into the Earth than previously recorded. The phenomenon may occur even in areas of the seafloor not marked by regions of plate subduction, the researchers say. 

"[The work] refutes long held assumptions that mid-ocean ridges might play a passive role in plate tectonics," senior researcher and geophysicist Mike Kendall from the University of Oxford explains in a press release.

"It suggests that in places such as the Mid-Atlantic, forces at the ridge play an important role in driving newly-formed plates apart," he continues.

Essentially, the researchers say that an upsurge of matter from deep underneath the Earth's crust might account for the fact that the Atlantic Ocean is slowly widening. Their study helps us gain a better understanding of tectonic plates, which are responsible for earthquakes, tsunamis, and volcanic eruptions.