Massive, hidden structures located nearly 1,800 miles beneath Earth’s surface—known as large low-shear-velocity provinces and ultra-low-velocity zones—may be the cooled remains of an ancient basal magma ocean altered by leaking core materials, according to a Rutgers-led study published in Nature Geoscience.
For many years, researchers have puzzled over two enormous and unusual features hidden deep inside Earth. Traditional ideas about how the planet formed and evolved have struggled to explain them. They alter the trajectories of seismic waves tearing through the planet. Yet, simulations of a cooling early Earth predicted a neatly stratified mantle, much like how frozen juice separates into sugary concentrate and watery ice.
Reality, as revealed by modern seismology, looks nothing like a neat geological layer cake.
Decoding the Anomalies at the Core-Mantle Interface
The deep-Earth landscape features two massive categories of anomalies. Large low-shear-velocity provinces, or LLSVPs, represent gargantuan masses of exceptionally hot and dense rock. One sits squarely beneath the African continent. Its twin rests deep under the Pacific Ocean. Alongside them lie ultra-low-velocity zones. These formations behave like thin, partly molten layers clinging to the core in puddle-like patches. Both structures severely retard seismic waves. That extreme deceleration points directly to material compositions and thermodynamic states vastly different from the surrounding lower mantle.
“These are not random oddities,” explained Yoshinori Miyazaki, an assistant professor in the Department of Earth and Planetary Sciences in the Rutgers School of Arts and Sciences, whose research team spearheaded the new interpretation. “They are fingerprints of Earth’s earliest history. If we can understand why they exist, we can understand how our planet formed and why it became habitable.”
Miyazaki and his collaborators noticed a glaring contradiction in planetary models. Earth spent its infancy encased in a global ocean of molten rock. As this ancient magma ocean cooled, many scientists expected that distinct chemical layers should have formed. Instead, seismic observations display uneven, complex piles heaped at the bottom of the mantle. The math refused to match the observations.
Core Leakage and the Basal Magma Ocean Hypothesis
To solve the puzzle, the research team looked inward, straight toward Earth’s core. Their model indicates that over billions of years, elements such as silicon and magnesium did not stay locked away safely in the core. Instead, they gradually escaped outward, diffusing across the boundary and seeping into the lower mantle.
This slow geochemical hemorrhage disrupted normal mantle crystallization. It prevented clean chemical layering and created the bizarre, dense compositions observed today. The research team interprets both LLSVPs and ultra-low-velocity zones as the direct, cooled descendants of an ancient “basal magma ocean” fundamentally warped and enriched by core-derived material leaking from below.
“What we proposed was that it might be coming from material leaking out from the core,” Miyazaki noted. “If you add the core component, it could explain what we see right now.”
By synthesizing seismic data, mineral physics, and geodynamic simulations, the team established a new framework. These deep-seated structures may help fuel volcanic hotspots on the surface, including the geological plumbing beneath Hawaii and Iceland.
Planetary Habitability and the Inner Solar System Divergence
The implications of core-mantle interactions extend far beyond mineralogy. The mechanics of how heat transfers from the core through these massive provinces may have influenced planetary volcanism, atmospheric evolution, and long-term climate stability. Researchers suggest that these deep interior processes hold the key to answering a fundamental question: why did Earth become a cradle for life while its planetary neighbors suffered radically different fates?
Earth possesses water, life, and a relatively stable atmosphere. Venus developed a state featuring an atmosphere roughly 100 times thicker than Earth’s, dominated by carbon dioxide. Mars turned cold and barren, with a very thin atmosphere.
“Earth has water, life and a relatively stable atmosphere,” Miyazaki said. “Venus’ atmosphere is 100 times thicker than Earth’s and is mostly carbon dioxide, and Mars has a very thin atmosphere. We don’t fully understand why that is. But what happens inside a planet, that is, how it cools, how its layers evolve, could be a big part of the answer.”
As geodynamicists continue refining models of core-mantle diffusion, these structures transition from mysterious seismic anomalies into vital archives. They record the birth of the planet and define the invisible subterranean boundaries that make surface life possible.
