Scientists have identified unusual structures deep within Earth’s mantle, raising new questions about the planet’s geological history, Space.com reports.
These “sunken worlds,” which resemble ancient fragments of Earth’s crust, appear in locations that defy conventional understanding of tectonic activity. The discovery stems from groundbreaking imaging techniques that provide unprecedented insights into Earth’s interior.
The research, published in Scientific Reports on November 4, 2024, utilized advanced seismographic imaging known as full-waveform inversion. This technique combines seismic data from earthquakes worldwide to create high-resolution 3D models of Earth’s interior. The approach revealed numerous previously unidentified mantle structures, some of which may be subducted slabs—remnants of Earth’s crust that were pushed into the mantle through tectonic plate collisions.
While subducted slabs are typically found near tectonic plate boundaries, such as those under the Pacific Ring of Fire, some of these newly discovered anomalies lie in regions with no history of tectonic activity. For example, blobs beneath the western Pacific Ocean are located far from known fault lines, leaving researchers puzzled about their origin.
Scientists propose several hypotheses for the mysterious blobs. They may represent:
- Ancient Crust Material: Remnants of Earth’s original crust formed billions of years ago during the planet’s early development.
- Mantle Growth: Dense materials that formed within the mantle over hundreds of millions of years.
- Unknown Processes: Other yet-to-be-identified geological processes that could explain their presence.
Despite these theories, the precise nature of the anomalies remains unknown.
“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,” said Thomas Schouten, a doctoral candidate at ETH Zurich’s Geological Institute.
The use of full-waveform inversion marks a significant leap in seismology. Unlike traditional methods that stitch together individual earthquake data, this approach integrates seismic waveforms into a unified image. The computational demands of this method required the Piz Daint supercomputer in Switzerland, one of Europe’s most powerful systems.
Andreas Fichtner, a seismologist and co-author of the study, likened the discovery to medical advancements.
“It’s like a doctor who, after decades of studying the circulatory system, suddenly finds an unexpected artery. That’s how we feel about these new findings.”
Researchers believe that the anomalies may share characteristics with subducted slabs, as seismic waves move through both at similar speeds. However, this does not conclusively prove they are the same. Future studies will focus on analyzing the material properties that influence seismic wave speeds to better understand the composition and origin of these anomalies.
The findings shed light on the complexity of Earth’s mantle and highlight how much remains to be learned about the planet’s inner workings. With further research, these “sunken worlds” may provide critical insights into Earth’s geological history and the dynamic processes shaping its interior.
