For many years, scientific minds have been perplexed by two vast geological formations concealed deep within our planet. These geological peculiarities might preserve geochemical traces that differentiate them from the surrounding mantle. Nevertheless, their genesis remains an unresolved enigma. Yoshinori Miyazaki, a geodynamicist from Rutgers University, and his research associates have put forth a compelling hypothesis to elucidate these anomalies and their influence on Earth’s capacity to sustain life.
The illustration shows a cutaway revealing the interior of early Earth with a hot, melted layer above the boundary between the core and mantle. Image credit: Yoshinori Miyazaki / Rutgers University.
The two perplexing structures, identified as large low-shear-velocity provinces and ultra-low-velocity zones, are situated at the interface between Earth’s mantle and its core, approximately 2,900 kilometers (1,800 miles) below the surface.
Large low-shear-velocity provinces are characterized as continent-sized agglomerations of dense, heated rock.
One such province resides beneath the African continent; the other is located under the expanse of the Pacific Ocean.
Ultra-low velocity zones are depicted as thin, molten regions that adhere to the core, akin to pools of lava.
Both categories of structures significantly decelerate seismic wave propagation, indicating an atypical composition.
“These are not mere random irregularities,” stated Dr. Miyazaki, a co-author of a publication featured in the journal Nature Geoscience.
“They represent imprints from Earth’s nascent history.”
“By comprehending their existence, we can gain insight into our planet’s formation and the factors contributing to its habitability.”
“Billions of years ago, Earth was enveloped by a global ocean of molten rock.”
“As it underwent cooling, scientists anticipated the mantle to stratify into distinct chemical layers, analogous to frozen juice separating into a sugary concentrate and watery ice.”
“However, seismic investigations do not reveal such pronounced layering. Instead, large-low shear velocity provinces and ultra-low velocity zones form irregular accumulations at the planet’s deepest region.”
“This discrepancy served as our point of departure. If we commence with the magma ocean and perform the requisite calculations, the results do not align with contemporary observations of Earth’s mantle. Something was evidently absent from our understanding.”
The research team’s computational model postulates that over eons, elements such as silicon and magnesium have leached from the core into the mantle, intermingling with it and thereby impeding the formation of robust chemical stratification.
This elemental infiltration may account for the peculiar composition of large low-shear-velocity provinces and ultra-low-velocity zones, which can be interpreted as solidified residues from what the researchers designated a basal magma ocean that had been adulterated by material from the core.
“Our hypothesis proposed that the origin might stem from material emanating from the core,” remarked Dr. Miyazaki.
“Incorporating the core component could provide an explanation for the phenomena we observe today.”
“This finding extends beyond the realm of deep-Earth geochemistry.”
“Interactions between the core and mantle may have influenced Earth’s cooling trajectory, the patterns of volcanic activity, and even the evolutionary path of its atmosphere.”
“This could potentially illuminate why Earth possesses oceans and life, while Venus is a scorching inferno and Mars is a frigid desert.”
“Earth is distinguished by the presence of water, life, and a comparatively stable atmosphere.”
“Venus’ atmosphere is a hundredfold denser than Earth’s and is predominantly composed of carbon dioxide, whereas Mars exhibits a tenuous atmosphere.”
“The precise reasons for these planetary divergences are not fully understood. However, the internal processes of a planet, specifically its cooling mechanisms and the evolution of its constituent layers, could represent a significant factor in the explanation.”
Through the synergistic integration of seismic data, mineral physics, and geodynamic modeling, the authors have reframed large low-shear velocity provinces and ultra-low-velocity zones as critical indicators of Earth’s developmental processes.
These structures might even contribute to the sustenance of volcanic hotspots, such as those found in Hawaii and Iceland, thereby establishing a link between the planet’s deep interior and its surface environment.
“This research exemplifies how the convergence of planetary science, geodynamics, and mineral physics can facilitate the resolution of some of Earth’s most enduring scientific puzzles,” observed Dr. Jie Deng, a collaborator on the study and a researcher at Princeton University.
“The notion that the deep mantle might still harbor the chemical echoes of early core–mantle interactions introduces novel avenues for comprehending Earth’s singular evolutionary trajectory.”
“Each incremental piece of evidence contributes to filling the voids in Earth’s early history, transforming disparate clues into a more coherent depiction of its development.”
“Even with a limited set of initial clues, we are beginning to construct a narrative that holds logical consistency,” stated Dr. Miyazaki.
“This investigation imparts a greater degree of certainty regarding Earth’s evolutionary path and the reasons for its exceptional nature.”
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J. Deng et al. 2025. Deep mantle heterogeneities formed through a basal magma ocean contaminated by core exsolution. Nat. Geosci 18, 1056-1062; doi: 10.1038/s41561-025-01797-y
