Geophysicists at ETH Zurich have uncovered surprising findings about the Earth’s mantle that challenge conventional plate tectonic theories. Using advanced seismic models, the researchers identified unexpected anomalies resembling submerged tectonic plates, located far from known subduction zones. These discoveries raise questions about the composition and dynamics of Earth’s interior and suggest the need to rethink established geological concepts.
Because the mantle is inaccessible to direct observation or sampling, scientists rely on indirect methods, like seismic wave analysis, to study its structure. When earthquakes occur, seismic waves propagate through the Earth, their speed influenced by the density and elasticity of the materials they traverse. By recording these waves, geophysicists map the Earth’s interior, much like doctors use ultrasound to visualize internal organs. Traditionally, such studies have pinpointed submerged tectonic plates in subduction zones—regions where one tectonic plate is pushed beneath another into the mantle. These findings have been central to understanding the plate tectonic cycle, which describes the creation and destruction of plates over geological time.
However, a new high-resolution model developed by ETH Zurich and the California Institute of Technology revealed anomalies that defy expectations. The researchers discovered mantle zones resembling remnants of submerged tectonic plates beneath large oceans and continental interiors, far from subduction zones. One such anomaly lies under the western Pacific, a region where current geological theories indicate no recent subduction activity. This unexpected finding was made possible by full-waveform inversion, a computationally intensive technique that analyzes all types of seismic waves for a more detailed view of the mantle. The study, published in Scientific Reports, marks a significant advancement in geophysical modeling.
The anomalies raise intriguing questions about their origin. Researchers speculate that these zones could be ancient silica-rich material, dating back to the mantle’s formation 4 billion years ago, that survived billions of years of mantle convection. Alternatively, they might represent areas where iron-rich rocks have accumulated as a result of convective movements within the mantle. While these theories are plausible, the exact composition and significance of these anomalies remain unknown.
To generate the model, the researchers used the Piz Daint supercomputer at the Swiss National Supercomputing Centre, highlighting the computational demands of such studies. Despite this technological leap, understanding the mantle’s complexity requires further refinement. Lead researcher Thomas Schouten explains that current methods primarily analyze wave speeds, which offer limited insight into the material properties of the mantle. Future studies will focus on correlating these speeds with specific compositions to better understand Earth’s interior.
The discovery of widespread anomalies resembling submerged tectonic plates suggests that Earth’s mantle is far more heterogeneous and dynamic than previously thought. These findings challenge long-standing assumptions about plate tectonics and highlight the potential for new models to transform our understanding of Earth’s history and processes. Continued research will be critical to uncover the mysteries of these anomalies and their implications for the planet’s geological evolution.
https://phys.org/news/2025-01-sunken-worlds-pacific-high-res.html