The oceans are not as equal as you might think. Scientists estimate that the Atlantic Ocean actually increases by several centimeters each year. At the same time, the Pacific is shrinking.
This slow glacial movement of the oceans is due to the continuous movement of the Earth’s tectonic plates as the plates beneath the Americas move away from those beneath Europe and Africa.
The deep geophysical forces underlying this epic phenomenon remain far from fully understood, but researchers could have identified an important contributor to what is happening.
In a new study, scientists suggest that mid-ocean ridges – mountain formations that appear along the seabed between tectonic plates – may be more involved in transferring material between the upper and lower mantle under the Earth’s crust than we have. previously performed.
The 39 locations of the seismometer. (University of Southampton)
“Diving boards and rising feathers are generally accepted as transfer sites, while ridges in the middle of the ocean are not usually assumed to play a role,” explains a team led by seismologist Matthew Agius in a new paper. from the University of Southampton in the UK.
“However, tight constraints from in situ ridge measurements proved to be challenging. “
To fill the gaps in our knowledge, the researchers deployed a fleet of 39 seismometers along the Atlantic bottom to record seismic movements under the Mid-Atlantic ridge – the boundary of the ridge that tectonically separates America from Europe and Africa.
The 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, allowing the team to imagine the transfer of material to depths as underground as 660 kilometers (410 miles) below the surface.
The results suggest that the ascent of the chemical material is not limited to shallow depths in the Mid-Atlantic ridge, but may occur at the deepest areas of the mantle transition zone, suggesting that the material in the lower mantle rises upward.
“The observations involve the transfer of material from the lower to the upper mantle – either continuously or dotted – which is related to the Mid-Atlantic ridge,” the researchers explain.
“Given the length and longevity of the mid-ocean ridge system, this implies that the convection of the entire mantle may be more widespread than previously thought.”
Implementation of one of the seismometers. (University of Southampton)
Although it was already known that mid-ocean ridges have contributed to the phenomenon of seabed spread, new findings show that the general processes involved extend much deeper into the Earth than previously measured and may occur even in seabed areas. marked by open plate subduction regions.
“[The work] refutes long-standing hypotheses that mid-ocean ridges may play a passive role in plate tectonics, “said lead researcher and geophysicist Mike Kendall of Oxford University.
“This suggests that in places like the mid-Atlantic, ridge forces play an important role in separating newly formed plates.”
The findings are reported in The nature.