Are there hidden, sunken worlds within Earth? A new study has revealed astonishing anomalies in the Earth’s mantle that challenge long-standing theories about plate tectonics.
Researchers from ETH Zurich and the California Institute of Technology have used advanced seismic imaging techniques to uncover mysterious zones deep within Earth, far from known subduction zones.
These findings, which could rewrite our understanding of Earth’s internal dynamics, were made using a high-resolution seismic imaging method called full-waveform inversion.
This advanced technique uses all types of earthquake waves, offering a much clearer view of the mantle’s composition than traditional methods.
What’s hiding in Earth’s mantle?
Traditionally, scientists believed that anomalies in the mantle — regions where seismic waves behave unusually — were mostly linked to subducted tectonic plates.
These plates sink into the mantle at plate boundaries, creating distinct zones of faster-than-normal wave speeds.
However, the new research has found anomalies in unexpected places: under vast ocean regions and within continental interiors.
These are areas with no known history of recent plate subduction.
“We’ve discovered that these areas, which look like remains of subducted plates, are much more widespread in the mantle than we ever thought,” says Thomas Schouten, the study’s first author and a doctoral student at ETH Zurich’s Geological Institute.
Breakthrough technology
The key to these groundbreaking insights is full-waveform inversion.
Unlike previous models that relied on limited seismic wave data, this method integrates all earthquake waves to create a highly detailed picture of Earth’s interior.
This computationally intensive process was made possible by the Piz Daint supercomputer at the Swiss Center for Scientific Computing in Lugano.
The result?
A high-definition map of the mantle, revealing zones with unexpected seismic wave behaviours.
One such anomaly was found beneath the western Pacific, where tectonic theories suggest no remnants of subducted plates should exist.
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What do these anomalies mean?
The discovery raises major questions about the material composition and origins of these zones.
“We see these anomalies everywhere in the mantle, but we still don’t know what material is creating these patterns,” says Schouten. “That’s our dilemma.”
Researchers speculate that these could be remnants of ancient material dating back 4 billion years.
One possibility is silica-rich rocks from Earth’s early formation, while another theory suggests iron-rich material accumulated over billions of years due to mantle convection.
Rewriting the tectonic textbook
This discovery challenges the widely accepted belief that subducted plates are the main source of anomalies in the mantle.
The presence of these zones in areas with no recent subduction history forces scientists to rethink existing theories about Earth’s internal structure.
“To fully understand these anomalies, we need to develop even better models that can dig deeper into Earth’s interior,” Schouten explains. “We need to figure out what material properties are responsible for the observed wave speeds — essentially, we need to understand the material behind the waves.”
The findings leave researchers with more questions than answers, but one thing is clear: Earth’s mantle holds secrets that could reshape our understanding of the planet.