Researchers have found evidence of a long-lost seabed beneath the Pacific Ocean that could rewrite Earth’s history.
They discovered remnants of an ancient seafloor that is likely part of a larger tectonic plate that broke off and slipped into the depths 250 million years ago.
Scientists mapped the structure and found it was unusually thicker and cooler than surrounding areas.
The ancient seafloor challenges existing theories about Earth’s internal structure and offers new insights into how the planet’s surface evolved over millions of years.
New research has found evidence of an ancient seafloor that complicates current theories about Earth’s interior
The seafloor sank beneath the Nazca plate about 250 million years ago
“Our discovery raises new questions about how the deep Earth influences what we see on the surface over vast distances and time scales,” lead author and postdoctoral geology researcher Jingchuan Wang of the University of Maryland said in a statement.
One of the study’s key findings challenges prevailing ideas about what happens to oceanic plates as they enter the Earth’s mantle.
Researchers discovered the 19-kilometer-thick and 2,000-kilometer-long region in the “mantle transition zone,” an area that separates the upper mantle from the lower mantle.
The prehistoric seafloor was found at the East Pacific Rise, a tectonic boundary on the floor of the southeastern Pacific Ocean.
“This thickened area resembles a fossilized fingerprint of an ancient piece of seabed that fell into the Earth about 250 million years ago,” Wang said.
Subduction often leaves behind visible evidence of movement, such as volcanoes, earthquakes and deep marine trenches.
But usually, oceanic plates are completely eaten by Earth, leaving no discernible trace on the surface, Wang said.
His research challenges this idea. Wang and his colleagues found that material moved through Earth’s interior much more slowly than previously thought.
The unusual thickness of the region the team discovered indicates the presence of colder material in this part of the mantle transition zone, and that some oceanic plates are becoming stuck midway within the mantle.
“We found that the material in this region was sinking at about half the rate we expected, suggesting that the mantle transition zone may act as a barrier and slow the movement of material through the Earth,” Wang explains .
Therefore, his research 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 insight could prompt scientists to revise models of plate tectonics and gain a more accurate understanding of how Earth’s surface has evolved over geological timescales.
“It gives us a glimpse into Earth’s past that we’ve never seen before,” Wang said.
The team also believes that the newly discovered seafloor could explain the Pacific Large Low Shear Velocity Province (LLSVP), a mysterious region of the lower mantle where seismic waves travel slower than average.
The unusual structure of the LLSVP has long puzzled scientists. But now Wang’s research 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 the province’s strange shape.
Wang and his team discovered this ancient seafloor through seismic imaging – a technique that allows researchers to collect data as seismic waves travel through different layers of the Earth.
The team suggested that the seafloor was a piece of an ancient tectonic plate that broke off 250 million years ago and sank to the bottom of the Pacific Ocean, creating a new seafloor.
‘You can think of seismic imaging as something similar to a CT scan. It has essentially allowed us to make a cross-section of the interior of our planet,” Wang said.
With this data, they were able to create a detailed map of this previously unknown structure hidden deep within the Earth’s mantle, revealing the anomalous structure.
The researchers believe this long-lost seafloor may belong to the Phoenix Plate, a tectonic plate that once dominated much of the Pacific Ocean before disappearing beneath another oceanic plate.
As the Phoenix plate sank deep into the Earth’s interior, it carried cooler material from the ocean floor to the hot mantle. This left a cold thermal signature that Wang and his colleagues were able to detect in their study.
The team plans to expand their research to other parts of the Pacific Ocean and beyond, with the aim of creating a more comprehensive map of ancient subduction and upwelling zones.
Upwelling is a geological process that occurs when submerged material warms and rises back to the surface.
They will also investigate what effects these zones have on structures both above and below the Earth’s surface.
“This is just the beginning,” Wang said.
‘We believe there are many more ancient structures waiting to be discovered in the deep interior of the Earth. Each has the potential to reveal many new insights into our planet’s complex past – and even lead to a better understanding of other planets beyond our own.’