The research team has discovered evidence of a previously unknown subduction zone beneath the Pacific Ocean, a discovery that could rewrite its geological history Earth.
Subduction zones are where Earth’s tectonic plates sink into each other. Researchers have discovered remains of an ancient subduction zone that is likely a piece of a large tectonic plate that ruptured and slid deep into Earth 250 million years ago.
The researchers mapped the structure located on the Nazca Plate, on the west coast of South America, about 1,500 km from Chile. They found that the structure is unusually thicker and colder than the surrounding regions. This unknown subduction zone shatters existing theories about Earth’s internal structure and provides new insights into how our planet’s surface evolved.
“Our discovery opens new questions about how the Earth’s depths affect what we see at the surface over vast distances and timescales,” geology postdoctoral principal investigator Yingchuan Wang of the University of Maryland said in a statement. USA, which led the investigation team. One of the study’s main conclusions challenges prevailing ideas about what happens to oceanic plates as they subduct into the Earth’s mantle.
The researchers discovered the 20 km thick and 1,800 km long region in the “mantle transition zone,” a region that separates the upper mantle from the lower mantle.
“This thickened area is like a fossilized fingerprint of an ancient piece of seafloor that sank into the Earth about 250 million years ago. The subduction process often leaves behind visible evidence of movement, such as volcanoes, earthquakes, and deep ocean trenches. But normally, oceanic plates are completely absorbed by the Earth relatively quickly, leaving no distinct traces on the surface,” said Wang, whose research challenges this view. Wang and his colleagues found that material moved through the Earth’s interior much more slowly than we thought.
The unusual thickness of the region the team discovered suggests the presence of cooler material in this part of the mantle transition zone, and that some oceanic plates are trapped midway as they subduct through the mantle.
“We found that in this region material was sinking at about half the speed we expected, suggesting that the mantle transition zone may act as a barrier and slow the movement of material through the Earth,” explains Wang.
The models
The new study that is published in the journal “Science Advances” shows that ancient subducted plates can be preserved deep within the Earth’s interior, affecting mantle structures for hundreds of millions of years.
This new idea could lead scientists to revisit models of plate tectonics and gain a more accurate understanding of how the Earth’s surface has evolved over different geological periods. “This gives us a glimpse into Earth’s past that we’ve never had before,” says Wang.
The team also believes the newly discovered depression could explain the Great Pacific Low Shear Province (LLSVP), a mysterious region of the lower mantle with seismic waves that travel slower than average.
LLSVP’s unusual structure has long intrigued scientists. But now, Wang’s study has revealed that the ancient seafloor may have split the LLSVP like a wedge as it fell into the mantle, offering a possible explanation for this region’s strange shape.
Naftemporiki.gr
