According to a team of geoscientists from the University of Maryland and the University of Maryland, between 250 million and 120 million years ago during the Mesozoic Era, the ancient ocean floor was formed by the East Pacific Rise, a plate boundary at the bottom of the southeastern Pacific Ocean. It is said to have sunk deep into the earth. University of Alberta.
A map of the East Pacific Ridge region where the ancient ocean floor was discovered. Image credit: Jingchuan Wang.
University of Maryland researcher Jingchuan Wang and his colleagues used innovative seismic imaging techniques to look deep into the Earth's mantle, the layer between the Earth's crust and core.
They discovered an unusually thick region in the mantle transition zone at depths of about 410 to 660 km below the Earth's surface.
This zone separates the upper and lower mantle and expands or contracts depending on temperature.
The newly discovered ocean floor may also explain the unusual structure of the Pacific Large Low Shear Velocity Province (LLSVP), a huge region in Earth's lower mantle. Because LLSVP appears to be divided by slabs.
“This thickened area is like a fossil fingerprint of an ancient ocean floor that sank into the Earth about 250 million years ago,” Wang said.
“This gives us a glimpse into Earth's past that we've never seen before.”
Subduction occurs when one tectonic plate slides beneath another and surface material is recycled into the Earth's mantle.
This process often leaves behind visible evidence of movement, such as volcanoes, earthquakes, and deep ocean trenches.
Geologists, on the other hand, typically study subduction by examining rock samples and sediments found at the Earth's surface.
By studying how seismic waves travel through the different layers of the Earth, researchers were able to create a detailed map of the structures hidden deep within the mantle.
“You can think of seismic imaging as similar to a CT scan. Essentially, it allows us to see a cross-section of the Earth's interior,” Dr. Wang said. .
“Typically, chunks of ocean material are completely consumed by the Earth, leaving no discernible traces on the surface.”
“But looking at ancient subducted slabs through this perspective has provided new insights into the relationship between the Earth's very deep structures and surface geology that were not previously clear.”
What the authors discovered surprised them. Matter was moving much more slowly through the Earth's interior than previously thought.
The unusual thickness of this region they found suggests the presence of cold material in this part of the mantle transition zone, where parts of the oceanic slab become stuck in the middle as they sink through the mantle. It suggests that there is.
“We found that material is sinking at about half the rate expected in this region. This may be due to the mantle transition zone acting like a barrier, slowing the movement of material through the Earth. “This suggests something,” Dr. Wang said.
“Our findings raise new questions about how the deep Earth influences what we see at the surface over vast distances and time scales.”
of result Published in a magazine scientific progress.
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Wang Jingchuan others. 2024. Intraoceanic subduction during the Mesozoic era formed the lower mantle beneath the East Pacific uplift. scientific progress 10(39);doi: 10.1126/sciadv.ado1219
Source: www.sci.news
