University of Maryland researchers have unveiled evidence of an ancient seafloor buried deep within Earth’s mantle. This breakthrough not only challenges existing theories on Earth’s internal structure but also offers a unique glimpse into our planet’s geological past.
University of Maryland scientists, led by postdoctoral researcher Jingchuan Wang, have uncovered extraordinary evidence of an ancient seafloor residing deep within Earth’s mantle, dating back to the time of dinosaurs. This discovery, situated at the East Pacific Rise — a tectonic plate boundary within the southeastern Pacific Ocean — challenges long-standing theories about the underground makeup and history of our planet.
Wang and his team, using state-of-the-art seismic imaging techniques, penetrated the Earth’s mantle to unprecedented depths. They discovered an abnormally thick area in the mantle transition zone, a pivotal layer situated between 410 to 660 kilometers beneath the Earth’s surface, which marks the boundary between upper and lower mantles.
“This thickened area is like a fossilized fingerprint of an ancient piece of seafloor that subducted into the Earth approximately 250 million years ago,” Wang said in a news release. “It’s giving us a glimpse into Earth’s past that we’ve never had before.”
Subduction, the process where one tectonic plate dives beneath another, often leaves clues such as earthquakes, volcanoes and marine trenches. However, rather than focusing on surface evidence, Wang, alongside Vedran Lekic, a geology professor, and Nicholas Schmerr, an associate professor of geology, examined seismic waves to map the mantle’s hidden structures.
“You can think of seismic imaging as something similar to a CT scan. It’s basically allowed us to have a cross-sectional view of our planet’s insides,” Wang added.
The team’s seismic imaging revealed an “ancient subduction slab,” offering new insights into the deep Earth’s relationship with surface geology.
Remarkably, the researchers found that material moves through Earth’s interior more slowly than previously thought. They speculate that the thickened mantle portion may contain colder material, indicating some oceanic slabs get stalled in the mantle transition zone.
“We found that in this region, the material was sinking at about half the speed we expected, which suggests that the mantle transition zone can act like a barrier and slow down the movement of material through the Earth,” added Wang. “Our discovery opens up new questions about how the deep Earth influences what we see on the surface across vast distances and timescales.”
Looking forward, the research team has set their sights on extending their exploration to other regions of the Pacific Ocean and beyond. Wang aims to create a more comprehensive map of ancient subduction and upwelling zones, enriching understanding of both deep and surface Earth structures.
“This is just the beginning,” Wang concluded. “We believe that there are many more ancient structures waiting to be discovered in Earth’s deep interior. Each one has the potential to reveal many new insights about our planet’s complex past — and even lead to a better understanding of other planets beyond ours.”
The study was published in the journal Science Advances.