The oceans are not as equal as one might think. Scientists estimate that the Atlantic Ocean grows by several centimeters each year. At the same time, the Pacific is shrinking.
This slow glacial displacement of the oceans is due to the continuous movement of the Earth’s tectonic plates, as the plates below the Americas move away from those below Europe and Africa.
The deep geophysical forces underpinning this epic phenomenon are still far from fully understood, but it is possible that researchers have just identified a major contributor to what is happening.
In a new study, scientists suggest that mid-ocean ridges (mountain formations that emerge along the seabed between tectonic plates) may be more involved in the transfer of material between the upper and lower mantle beneath the crust of the Earth of what we realized earlier.
The 39 locations of the seismometer. (University of Southampton)
“Sinking slabs and rising feathers are generally accepted as transfer sites, while mid-ocean ridges do not usually play a role,” explains a team led by seismologist Matthew Agius of the University of Southampton. in the United Kingdom.
“However, strict restrictions on in situ dorsal measurements have proven to be a challenge. “
To fill the gaps in our knowledge, the researchers deployed a fleet of 39 seismometers at the bottom of the Atlantic to record seismic movements under the Mid-Atlantic ridge, the boundary of the ridge that tectonically separates the Americas from Europe and Africa.
Seismic readings recorded in the experiment monitored the flow of material in the transition zone of the mantle between the upper mantle and the lower mantle, which allowed the team to transfer material to such subterranean depths. as 660 kilometers (410 miles) below the surface.
The results suggest that chemical material surges are not limited to shallow depths in the mid-Atlantic range, but may emerge at the deeper ends of the mantle transition zone, suggesting that the lower mantle material rises upwards.
“The observations involve a transfer of material from the lower to the upper mantle (either continuous or dotted) that is related to the mid-Atlantic ridge,” the researchers explain.
“Given the length and longevity of the mid-ocean ridge system, this implies that full-mantle convection may be more prevalent than previously thought.”
Deployment of one of the seismometers. (University of Southampton)
Although it was already known that the ridges of the middle ocean contributed to the phenomenon of seafloor propagation, the new findings show that the general processes involved extend much further to Earth than previously measured, and they can still occur even in areas of the seabed. marked by open plate subduction regions.
“[The work] refutes long-standing assumptions that mid-ocean ridges could play a passive role in plate tectonics, “says Mike Kendall, a senior researcher and geophysicist at Oxford University.
“It suggests that in places like the mid-Atlantic, ridge forces play an important role in separating newly formed plates.”
The findings are reported in Nature.