Scientists have identified six previously unknown structures deep within Earth’s mantle, using AI to analyze seismic data from over 2 million earthquakes between 1900 and 2024. The findings, published in the Journal of Geophysical Research: Solid Earth, reveal irregularities near the core-mantle boundary, 1,800 miles beneath the surface, that could reshape understanding of planetary formation and seismic activity.
Researchers at the Chinese Academy of Sciences uncovered six thermochemical piles hidden in Earth’s deep interior by training an artificial intelligence model to detect faint seismic signals known as PKP precursors. These structures, located at the boundary between the mantle and liquid outer core, were previously undetectable due to their subtle influence on seismic waves. The study, which analyzed data from 5,000 earthquakes, identified 174,929 high-quality PKP precursor signals—more than ten times the total from all previous studies combined.
AI Revolutionizes Seismic Analysis
The breakthrough hinged on machine learning, which automated the detection of PKP precursors—a task previously reliant on manual, laborious screening. Manual identification of these precursors is inefficient, subjective, and insufficient for vast global seismic data sets, the researchers noted in their study. By training an algorithm on human-verified signals, the team uncovered six regions with significant heterogeneities that had never been documented before. These areas, spanning continents and ocean basins, appear to form continuous bands rather than isolated patches, challenging prior assumptions about the Earth’s deep structure.
Whereas previous studies could only identify sparse, isolated patches sampled by precursors, our results reveal that these potential heterogeneities may extend across broad regions, the researchers concluded.
Structures May Hold Clues to Planetary History
The newly mapped irregularities could contain material from Earth’s early history, including fragments of the protoplanet Theia, which collided with Earth 4.5 billion years ago to form the Moon. The Daily Mail reported that these structures might consist of pieces of the continental crust or remains of Theia, transformed by the extreme pressures and temperatures at the core-mantle boundary. Under such conditions, rock can partially melt or undergo mineralogical changes, creating distinct thermal and chemical signatures.
The study’s authors suggested that mapping these features could improve predictions of seismic events by revealing how heat and material flow between the core and mantle influence mantle plumes and plate movements.
Structures’ Depth and Accessibility
The newly identified structures lie far beyond humanity’s physical reach. The deepest artificial point on Earth, Russia’s Kola Superdeep Borehole, extends approximately 7.6 miles below the surface. That means the structures are more than 230 times deeper than humans have ever drilled. Because Earth’s deepest layers remain inaccessible, scientists rely on seismic waves generated by powerful earthquakes to investigate the planet’s interior. According to the Daily Mail, researchers in China used artificial intelligence to examine more than 2 million seismic recordings from roughly 5,000 earthquakes.
Seismic Waves and Core-Mantle Boundary Dynamics
The AI model searched for PKP precursors, faint seismic waves that arrive shortly before stronger earthquake waves. These signals scatter when they encounter differences in density or composition deep inside Earth, allowing scientists to detect structures that otherwise remain invisible. Finding those weak signals manually has traditionally been difficult and time-consuming. The researchers emphasized that the core-mantle boundary (CMB) is where Earth’s lower mantle meets its (almost) liquid core. Until now, scientists have detected mostly larger seismic waves in that area.
However, the issue with these precursor signals (which often precede more powerful seismic waves called PKIKP) is that they have often been too faint to detect.
Temperature and Material Transfers at the Core-Mantle Boundary
At the core-mantle boundary, there is an enormous temperature jump, with a difference of about 1,000°C (1,800°F) from one layer to another. The massive heat escaping from the outer core drives convection currents in the mantle known as “mantle plumes.” These plumes can rise to the surface, creating volcanic activity. The study’s authors noted that the six newly identified structures may be part of this dynamic process, influencing how heat and material are transferred between the core and mantle.
Next Steps and Unanswered Questions
While the AI-driven analysis provides the most comprehensive map of the core-mantle boundary to date, many questions remain. The exact composition of the six structures is still unknown, and their role in Earth’s geological evolution requires further study. Researchers are now focusing on refining models of the lowermost mantle to determine how these heterogeneities affect seismic wave propagation and mantle convection.
The study’s findings also raise new questions about the dynamic nature of Earth’s interior. As AI continues to process seismic data, scientists anticipate more discoveries that could redefine models of planetary formation and seismic risk assessment.
