Scientists at ETH Zurich have made a groundbreaking discovery that challenges our current understanding of the Earth’s plate tectonics. Using high-resolution models, they found areas beneath large oceans and continents where earthquake waves behave differently, indicating zones of rocks that are colder or have different compositions than surrounding rocks.
Geophysicists use indirect methods to study the Earth’s interior, as no one can see inside the planet or drill deep enough to collect samples from the mantle. They analyze seismograms, or earthquake recordings, to determine the speed at which seismic waves propagate and calculate the internal structure of the Earth. This method is similar to how doctors use ultrasound to image organs without opening them up.
The researchers used a new approach called full-waveform inversion, which involves analyzing all types of earthquake waves, not just one. This computationally intensive process revealed anomalies in the Earth’s mantle that suggest zones of cold rock or unusual composition.
One such zone is located under the western Pacific Ocean, where there should be no material from subducted plates according to current plate tectonic theories. The researchers are unsure what material is involved and how it affects the Earth’s internal dynamics.
“It’s like a doctor who has been examining blood circulation with ultrasound for decades and finds arteries exactly where he expects them,” says ETH professor Andreas Fichtner. “Then if you give him a new, better examination tool, he suddenly sees an artery in the buttock that doesn’t really belong there.”
The discovery has sparked speculation about the origins of these anomalies, which could be ancient silica-rich material or zones where iron-rich rocks accumulate as a result of mantle movements over billions of years. The researchers emphasize the need for further research with even better models to uncover more details about the Earth’s interior.
“We have to calculate the different material parameters that could generate the observed speeds of the different wave types,” says Thomas Schouten, first author of the study.
Source: https://phys.org/news/2025-01-sunken-worlds-pacific-high-res.html