Exploring the depths of our planet’s interior poses a monumental challenge, far surpassing even the feats of interplanetary exploration. Humanity has ventured over 25 billion kilometers into the vastness of space, yet the deepest borehole ever drilled penetrates a mere 12 kilometers beneath the Earth’s surface. This stark contrast highlights how little direct access we have to the enigmatic regions that lie thousands of kilometers below us. Among these inaccessible zones, the boundary between the Earth’s lower mantle and its outer core — about 2,900 kilometers deep — remains a profound mystery, one that recent research has now begun to illuminate through the lens of geomagnetism.
This groundbreaking study, conducted by a team led by researchers at the University of Liverpool and published in Nature Geoscience, reveals compelling magnetic evidence that enormous, ultra-hot rock formations situated at the base of the mantle substantially influence the behavior of the underlying liquid iron in the outer core. These colossal solid structures, located beneath Africa and the Pacific Ocean, are not merely passive geological features but active agents molding the planet’s magnetic dynamics. Encircled by colder rock formations spanning from pole to pole, these mantle “blobs” contribute profoundly to the nature and stability of Earth’s magnetic field over geological timescales.
The quest to decipher the history of Earth’s magnetic field—and its interaction with deep mantle heterogeneity—is fraught with difficulty. Measuring ancient magnetic signatures embedded in rocks requires meticulous palaeomagnetic techniques, as these signals are subtle and prone to alteration over millions of years. Complementing these observations with advanced numerical models of the geodynamo—the process whereby the convective motion of liquid iron in the outer core generates Earth’s magnetic field—has enabled the research team to reconstruct magnetic behavior over the past 265 million years with unprecedented detail. Such simulations necessitate the use of supercomputers, utilizing extraordinary computational resources to simulate fluid dynamics and magnetic field generation over vast temporal domains.
Results from this integrative approach revealed striking thermal heterogeneity at the upper boundary of the outer core. Rather than being thermally uniform, this boundary zone exhibits pronounced temperature contrasts. Regions capped by the massive, scorching mantle structures are associated with reduced convective vigor in the underlying liquid outer core. This thermal disparity suggests that the flow of molten iron beneath these hot zones stagnates, while more vigorous fluid motions occur underneath cooler mantle regions. The implications of this finding fundamentally challenge the simplistic models that have traditionally treated the core-mantle boundary as relatively homogenous.
In addition to presenting a thermally complex picture at the core-mantle interface, the study uncovered patterns in the geomagnetic field stability. Certain portions of the magnetic field appear to have maintained remarkable stability for hundreds of millions of years. Conversely, other aspects have evolved and fluctuated over time, underscoring the dynamic interplay between deep Earth processes and surface observations. This temporal variability also influences our understanding of geological phenomena such as plate tectonics, continental drift, and the assembly and fragmentation of supercontinents like Pangaea.
Professor Andy Biggin, a leading figure in geomagnetism at the University of Liverpool, elaborated on the significance of these findings. He emphasized that the pronounced temperature variations in the mantle just above the core fundamentally alter the flow patterns of liquid iron in the outer core. Beneath hotter regions, where the mantle “blobs” reside, the iron may stagnate, disrupting the otherwise vigorous and continuous convection essential for maintaining Earth’s magnetic dynamo. This nuanced understanding strengthens the conceptual framework for using ancient magnetic records to infer the deep Earth’s evolutionary history and its persistent geodynamic properties.
Moreover, these results carry substantial implications beyond geomagnetism. Geological and climatological models that have historically assumed an idealized, perfectly aligned Earth magnetic field may need revision. Such assumptions underpin reconstructions of past continental configurations, interpretations of ancient climate proxies, and assessments of palaeobiological dynamics. The discovery that the magnetic field’s averaged behavior over long periods diverges from the traditional axial dipole model opens new avenues for refining models in natural resource formation and tectonic reconstructions.
The unique combination of palaeomagnetic evidence with sophisticated computer simulations represents a paradigm shift in deep Earth studies. The evolving understanding of how mantle heterogeneity influences the geodynamo enriches the scientific narrative about Earth’s interior, bridging the gap between surface geology and deep planet dynamics. This study exemplifies the interdisciplinary approach necessary to tackle some of the most challenging questions in Earth sciences, leveraging computational physics, mineralogy, and geomagnetism within a cohesive framework.
Central to this research is the DEEP (Determining Earth Evolution using Palaeomagnetism) group at the University of Liverpool, a team specializing in decoding magnetic signals locked in rocks worldwide. Since its establishment in 2017, supported by the Leverhulme Trust and the Natural Environment Research Council (NERC), DEEP has pioneered novel methodologies to reconstruct the geomagnetic field’s intricate history. Their efforts have brought fresh perspectives on how the inner workings of our planet affect the magnetic field observable at the surface, facilitating breakthroughs in geodynamic modeling.
The integration of palaeomagnetic data with numerical geodynamo simulations required cutting-edge supercomputing capabilities. Modeling the convective motions of the electrically conductive, liquid iron core over hundreds of millions of years entails solving complex magnetohydrodynamic equations in three dimensions. The research team’s success demonstrates the growing power of computational geosciences to reveal the cryptic processes that govern Earth’s magnetic and thermal evolution.
In summary, this pioneering investigation challenges longstanding ideas about Earth’s magnetic field formation by highlighting the role of temperature heterogeneity at the core-mantle boundary, driven by massive mantle rock structures. It illuminates the dynamic nature of the planet’s interior, its influence on magnetic field patterns, and the broader geological processes shaping Earth’s history. As researchers continue to refine models of Earth’s deep interior, these findings will undoubtedly foster new directions in palaeomagnetism, tectonics, and planetary science, fundamentally enriching our grasp of Earth’s inner life.
Subject of Research: Deep Earth mantle heterogeneity and its influence on Earth’s ancient magnetic field
Article Title: Mantle heterogeneity influenced Earth’s ancient magnetic field
News Publication Date: 3-Feb-2026
Web References: https://www.nature.com/articles/s41561-025-01910-1
References: DOI: 10.1038/s41561-025-01910-1
Keywords: Earth sciences
