- Tectonic plates under the Americas, Europe and Africa are being separated from year to year as the width of the Atlantic Ocean.
- New research shows what separates the plates: material from deep within the Earth is bursting upward on an underseat ridge in the middle of the Atlantic.
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The Atlantic Ocean becomes 1.5 inches wide every year.
This is because the tectonic plates passing through America are diverging from the underside of Europe and Africa. But precisely how and why that is happening has been a mystery to scientists, because the geological forces that push apart plates are generally not prevalent in the Atlantic.
A study released on Wednesday finally answers that question. Research published in the journal Nature suggests that a large underwater mountain range in the middle of the ocean holds the key to the Atlantic’s expansion.
This set of underseat peaks is known as the Mid-Atlantic Ridge, and it separates the North American Plate from the Eurasian Plate, and the South American Plate from the African Plate. The researchers behind the study found that material from deep within the Earth was rising to the surface under the Mid-Atlantic Ridge, pushing the plates to either side of the divide.
Atlantic seafloor spreading
Imagine the Earth as a chocolate truffle – a sticky center in a rigid center.
The center consists of a 1,800-mile-thick, semi-solid mantle enclosing a super-hot core. The upper layer of the truffle – only about 21 miles thick – is an earth crust, fragmented into tectonic plates that fit together like a puzzle. These plates appear above the mantle, rotating as hot, less dense material within the earth moves towards the crust, and the colder, denser material sinks toward the core. This process, known as convection, typically occurs when two plates collide and one subduct or sinks.
Typically, any upward tilt of material under tectonic boundaries, like the Mid-Atlantic Ridge, usually begins with a portion of the crust about 2 miles closer to the Earth’s surface. Material from the lower mantle, the part closest to the core, is not usually found there bursting the crustward.
But the new study found that the Mid-Atlantic Ridge is a convection hotspot.
Researchers measured geologic activity over a period of 621 miles. They dropped 39 seismometers under the waves in 2016, then left them for a year to collect data from earthquakes around the world. The seismic waves rotating through the material in the Earth’s core gave scientists a glimpse under the Mid-Atlantic Ridge.
The group found that magma and rock from 410 miles under the crust could make their way to the surface there. The uplift of the material that is extending the tectonic plates – and the continent at the top – furthermore at a rate of 1.5 inches (4 cm) per year.
“Rising from the lower to the upper mantle and all the way to the surface is usually associated with localized locations on Earth, such as Iceland, Hawaii and Yellowstone, and not with ridges from the mid-ocean,” psychologist Trey, a seologist at Roma University and co-author of the new study, told Insider. “This is what makes this result exciting because it was completely unexpected.”
Often, material trying to make its way from upper to lower mantle is interrupted by a band of dense rock, known as the mantle transition zone, between 255 miles and 410 miles under our feet. is.
But Agius and his colleagues speculated that the temperature in the deepest part of that transition zone, below the Mid-Atlantic Ridge, was higher than expected, thinning the area in the region. Therefore the material can move more easily to the ocean floor than other parts of the earth.
Solve a geological mystery
The discovery helps solve a long-term geological puzzle.
Researchers knew that oceans expand and contract at different rates. They also knew that plates run most distinctly in subduction zones, which are usually on the active continental margin – where the boundary between a continent and an ocean is also a tectonic plate boundary. This is why the Pacific Ocean spreads faster than the Atlantic: most of the Pacific sits atop a tectonic plate, and has boundaries almost entirely along the line on the eastern and western sides, the North American and Eurasian plates. Abduction at these boundaries causes earthquakes and volcanic eruptions that give the region the name “Ring of Fire”.
The Atlantic Ocean, however, sits on four major plates with boundaries that do not match continental boundaries – the boundaries lie in the middle of the ocean. Therefore, scientists were adamant on how Sefor was expanding.
But new research suggests that the lifting of material from deep within the mantle may be the engine of that Atlantic expansion.
The process began 200 million years ago, said Katherine Richert, a geophysicist at the University of Southampton and co-author of the new study. But someday, the pace of expansion may accelerate.
“Most probably the rate will remain the same during our lifetime. However, it is likely that the rate will change over millions of years, as it has varied in the past,” Rickert told Insider.