Deep Earth’s Hidden Structures Influence Magnetic Field, New Research Reveals
Scientists are gaining a deeper understanding of the forces shaping Earth’s magnetic field, discovering that massive, intensely hot rock formations deep within the planet’s mantle play a significant role. A new study, published in in Nature Geoscience, details how these structures influence the movement of liquid iron in Earth’s core, leading to both stable and dramatically changing magnetic field behaviors.
Reaching the Earth’s deepest regions presents a formidable challenge. While humans have traveled billions of kilometers into space, drilling efforts have only penetrated just over 12 kilometers beneath the surface. This limitation underscores the difficulty in studying the boundary between the mantle and the core – a critical internal region now the focus of intense research.
Giant Hot Rock Formations Beneath Africa and the Pacific
The research, led by the University of Liverpool, identified two massive hot rock formations located approximately 2,900 kilometers below Africa and the Pacific Ocean. These structures, described as continent-sized blobs of dense, hot rock surrounded by cooler material, have been influencing Earth’s magnetic field for millions of years. The findings suggest a complex interplay between these formations and the liquid outer core.
Understanding how Earth’s mantle deforms is crucial to understanding plate tectonics. A related study, also from the University of Liverpool, focused on the deformation of olivine, the most common mineral in the upper 400 kilometers of Earth. Researchers used advanced electron microscopy techniques, specifically Electron Backscatter Diffraction (EBSD) and Transmission Electron Microscopy (TEM), to analyze the microscopic structure of olivine crystals.
Traditionally, scientists have recognized two primary directions of dislocation movement within olivine – designated “a” and “c”. Dislocations are linear imperfections in the crystal lattice that allow the material to change shape under stress. However, a third direction, “b”, was generally considered rare, and insignificant. The new research challenges this assumption.
The Unexpected Role of ‘b’ Dislocations
The team’s analysis revealed that a surprisingly significant proportion – around 17% – of the olivine crystals studied exhibited evidence of deformation involving these previously overlooked “b” dislocations. Further confirmation came from direct imaging of these dislocations using TEM, validating the EBSD findings.
Our findings suggest that these dislocations may be more widespread than previously thought, improving our understanding of how the Earth’s mantle deforms,
said Professor John Wheeler, George Herdman Professor of Geology at the University of Liverpool and lead author of the study published in Geophysical Research Letters.
The presence of “b” dislocations may be influenced by factors such as pressure, temperature, and stress levels. Measuring these dislocations in natural samples could potentially help scientists determine the depth at which deformation occurred and the conditions experienced during that process. This provides a new avenue for investigating the dynamic processes within the Earth’s mantle.
A New Approach to Crystal Analysis
Beyond the specific findings about olivine deformation, the study also highlights the power of EBSD as a rapid screening tool. EBSD allows researchers to quickly identify regions within crystals that warrant further investigation using higher-resolution techniques like TEM. This combined approach streamlines the process of analyzing complex crystal structures.
The approach we’ve used could help scientists develop a better understanding of geological processes inside the Earth,
Professor Wheeler added. It may also have wider applications in materials science. For instance, olivine has crystal similarities to perovskites which have numerous industrial uses. Some materials such as semiconductors contain dislocations because of the manufacturing process which are deleterious to performance, so their abundance and arrangements need to be investigated.
Implications for Understanding Earth’s Interior and Beyond
The discovery of these deep-Earth structures and the refined understanding of olivine deformation have broader implications. The structures beneath Africa and the Pacific may even be linked to volcanic hotspots like Hawaii and Iceland, suggesting a connection between the deep Earth and surface phenomena. This research builds on previous work linking these anomalies to Earth’s molten beginnings and its unique ability to support life.
The findings also extend beyond planetary science. The insights gained from studying olivine’s deformation could be valuable in materials science, particularly in the development and optimization of materials like perovskites and semiconductors, where controlling crystal defects is critical for performance. The ability to rapidly identify areas of interest within crystals using EBSD promises to accelerate materials research across various disciplines.
The study, titled “Olivine Deformation: To B Slip or Not to B Slip, That Is the Question,” is published in Geophysical Research Letters (/doi.org/10.1029/2025GL117138).
