The Earth has always been full of mysteries, and new discoveries constantly unravel these puzzles, questioning our understanding of the world we live in. But what if what we perceive is only a fraction of reality? Imagine that beneath the surface lies a hidden dimension, a realm of ancient secrets and unknown forces that outline our existence. Could there be more to life than what our eyes just see? These questions challenge us to look beyond the visible directly into the unknown territories of our planet.
Recently scientists discovered potential patches of Earth’s ancient crust, called “sunken worlds,” that have been identified deep within the mantle. These mysterious blobs have been detected through a new method of mapping our planet’s interior in unexpected locations and have changed our traditional understanding of tectonic activity. These findings were published in the journal Scientific Reports and have opened up new directions for understanding Earth’s geological history and the dynamic processes occurring beneath our feet.
For decades, scientists have used seismographs to create 3D images of Earth’s interior by analyzing how seismic waves from earthquakes reverberate through the planet. This method has helped identify ancient sections of the crust, known as subducted slabs, pulled into the mantle through subduction zones where tectonic plates converge. In October 2024, researchers discovered a section of seafloor that had sunk into the mantle below Easter Island.
In the study published on 4 November 2024, researchers revealed that the creation of several expected subducted slabs within Earth’s interior had been shown with a technique known as seismographic imaging. Researchers have released some information about blob sizes, forms, and specific blob locations.
However, contrary to previously determined subducted slabs found over areas with known tectonic collisions, some new anomalies lie under regions without any recorded tectonic collisions below the western Pacific Ocean. This is such an unexpected result that scientists now struggle with the question of how these slabs came to these locations.
“That’s our dilemma,” explained Thomas Schouten, a doctoral candidate at the ETH Zurich Geological Institute in Switzerland, in a statement released on January 7. “With the new high-resolution model, we can see such anomalies everywhere in the Earth’s mantle. But we don’t know exactly what they are.”
One plausible explanation for the newly mapped blobs is that they consist of crust-like material left over from the mantle’s creation 4 billion years ago. On the other hand, they might be composed of other dense materials that have formed within the mantle over the past few hundred million years. Despite these theories, the true nature of these blobs remains a “major mystery,” as described by ETH Zurich representatives.
The overall understanding of Earth’s interior prior to this study was fashioned out of the seismographs produced globally by separate individual earthquakes. In contrast, the method utilized in this research, full-waveform inversion, brings together all these seismographs into a single, clear image through the use of computer models. In fact, this computationally thorough technique needed the Piz Daint supercomputer at the Swiss National Supercomputer Center in Lugano to process all the data.
Thue Fichtner, who was the co-author of the study and a developer at ETH Zurich, believes that the development was as significant as a breakthrough in medical imaging, “Imagine a doctor has been studying the circulatory system for decades,” Fichtner said. “Then, if you give [them] a new, better examination tool, [they] suddenly see an artery in the buttock that doesn’t really belong there. That’s exactly how we feel about the new findings.”
Researchers believe that the newly discovered blobs may be subducted slabs due to the similar speeds at which seismic waves travel through them. However, this does not confirm their identity, making sure that further research determines their true nature. “We have to calculate the different material parameters that could generate the observed speeds of the different wave types,” Schouten said. “Essentially, we have to dive deeper into the material properties behind the wave speed.”
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