The “fossilized fingerprint” of a section of seabed hidden in the Earth’s mantle beneath the Pacific Ocean has been found by scientists.
According to a recent study, this fingerprint is consistent with a crustal slab that started to sink into the mantle 250 million years ago, during the beginning of the dinosaur era (252 million to 66 million years ago). This slab, which formerly made up a portion of the seafloor in the southeast Pacific, may be able to explain an odd rift in the mantle, the layer of crust that lies halfway between Earth and the planet’s core.
Scientist Jingchuan Wang, a postdoctoral associate at the University of Maryland and seismologist, led the study’s writing. “It’s giving us a glimpse into Earth’s past that we’ve never had before,” she told reporters.
In the mantle transition zone, the sunken slab is currently positioned between the upper and lower mantles. The statement states that this transition zone extends between 255 and 410 miles (410 to 660 kilometers) deep beneath the surface of the Earth, albeit it is subject to expansion and contraction based on heat currents that circulate in the mantle.
While investigating the mantle beneath the East Pacific Rise, a rapidly developing mid-ocean ridge situated 2,000 miles (3,200 km) off the coast of South America, Wang and his associates discovered the slab. The varieties of rock beneath the seafloor were investigated by the researchers using seismic waves, and they also produced a computerized cross-section of the Earth’s crust and mantle. The group’s research was released in the journal Science Advances on September 27.
Related: A recent study suggests that massive waves in Earth’s mantle could cause continents to rise.
The cross-section showed that, around 220 miles (350 km) east of Rapa Nui, or Easter Island, there is an exceptionally thick mantle transition zone beneath a segment of the East Pacific Rise. “This thickened area is like a fossilized fingerprint of an ancient piece of seafloor that subducted into the Earth,” Wang stated.
When two tectonic plates collide and one plunges beneath the other, subduction takes place. Typically, subducting plate material breaks down in the mantle, where intense heat turns rocks back into magma. Amazingly, the recently found slab managed to avoid that fate.
“Usually, oceanic slabs of material are consumed by the Earth completely,” Wang stated.
According to the statement, the slab’s location suggests that it passed through the mantle at a pace that is roughly half of what scientists would typically anticipate for a subducting plate. According to Wang, this implies that the mantle transition zone has the ability to function as a viscous barrier and slow the flow of sinking material.
A peculiar gap in the mantle right beneath the thickened section of the transition zone may be explained by the slab. The research site is perched above the Pacific Large Low Shear Velocity Province (LLSVP), a region of Earth’s lower mantle where seismic waves significantly slow down.
As material moves to make room for the slab’s shape, the mass of the trapped slab inside the transition zone may be pushing the zone’s bottom limit into the LLSVP. This would result in a gap in the LLSVP.
Additionally, the discovery provides a fresh perspective on plate tectonics research. Wang declared, “This is just the beginning.” “We think that deep within the Earth’s innards are many more ancient buildings that are just waiting to be found. Each one has the capacity to provide a wealth of fresh perspectives on the complicated past of our planet and may even advance our knowledge of planets beyond our own.”
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