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The contemporary concept of the plate tectonic cycle suggests that remnants of submerged plates will likely be located near subduction zones. However, a new detailed model reveals that these remnants can also be found far away from subduction zones, challenging the long-standing geological narrative. The researchers propose that these distant remnants could be silica-rich deposits dating back to the mantle’s formation four billion years ago, or areas where iron-rich rocks have accumulated over billions of years.
In science, certain phenomena are difficult to observe directly. Exploration beyond our Solar System and the complexities of the quantum realm often require advanced methods. Similarly, understanding the composition of our planet is frequently beyond immediate reach. Geologists, like astronomers and quantum physicists, have devised innovative techniques to study the Earth’s interior without the need for large, impractical instruments. By deploying seismographic stations to monitor seismic waves passing through the Earth, scientists can analyze the planet’s interior and identify regions where submerged plates formed near subduction zones.
Using the powerful Piz Daint supercomputer in Lugano, Switzerland and a technique called full-wave inversion, a team of scientists from the California Institute of Technology and ETH Zurich produced a new high-resolution model of the lower mantle. Surprisingly, the model revealed remnants of submerged plates in unexpected locations, such as beneath oceans and within continents, far from any known subduction zones. These findings were published in the journal Scientific Reports.
One intriguing example is in the western Pacific, where the presence of a submerged plate contradicts recent geological history that suggests no nearby subduction zone. Andreas Fichtner, the senior author of the study from ETH Zurich, likened this discovery to a doctor identifying a new blood vessel through advanced imaging technology.
While this discovery challenges current understanding of Earth’s composition, the researchers suggest possible explanations for this tectonic anomaly. Thomas Schouten, the study’s first author from ETH Zurich, proposed that the anomalies could be remnants of ancient, silica-rich material existing since the mantle’s formation or regions where iron-rich rocks have accumulated over time.
“Rocks accumulate as a result of these mantle movements over billions of years. However, a drawback of using an indirect observation method is that numerous questions persist, particularly regarding the materials that could be influencing these seismic wave velocities. Researchers are optimistic that improved models will unveil the material properties underlying these puzzling mysteries far beneath the Earth’s surface.”
