Every year, the Americas are moving further away from Europe and Africa. The separation between the Atlantic-facing continents increases by 4 centimeters (1.6 inches) per year, but what was driving this has been a bit of a puzzler. The dividing line where new plates are formed is known as the Mid-Atlantic Ridge. A ridge is usually driven by a balancing act between the lighter and heavier parts of tectonic plates. But this is not the case for the Atlantic ocean, which is not surrounded by dense sinking plates.
In a new paper published in Nature, researchers suggest a new mechanism to explain this process: the region experiences an upsurge of matter from the deeper layers of our planet, which is pushing the continents apart.
One possibility was an upwelling of material from the mantle, the region beneath the Earth’s crust. These tend to originate at depths of 60 kilometers (37 miles) but the one driving the Mid-Atlantic Ridge is much deeper, over 10 times those depths.
To work out this mystery the team of researchers embarked on two research cruises deploying 39 seismographers at the bottom of the Atlantic ocean on each side of the ridge. This is one of the few experiments to have studied the mantle below the ocean's floor in such detail. In fact, it delivers the first large-scale and high-resolution imaging of the mantle.
“This was a memorable mission that took us a total of 10 weeks at sea in the middle of the Atlantic Ocean. The incredible results shed new light in our understanding of how the Earth's interior is connected with plate tectonics, with observations not seen before,” lead author Dr Matthew Agius, from Università degli studi Roma Tre, said in a statement.
In particular, they studied how structures changed between depths of 410 and 660 kilometers (255 and 410 miles). They also observed abrupt changes to mineral phases, which suggests the presence of an upwelling.
The findings suggest that the Mid-Atlantic Ridge is an active player in the plate tectonics of the region. Since, plate tectonics influence earthquakes and volcanoes, as well as sea levels, understanding their role helps us improve our planetary and climate models, leading to better warning systems for natural disasters.
“This was completely unexpected. It has broad implications for our understanding of Earth's evolution and habitability,” co-author Dr Kate Rychert from the University of Southampton, added. “It also demonstrates how crucial it is to gather new data from the oceans. There is so much more to explore!”