Scientists have proposed a new model for two massive structures deep inside Earth, suggesting they formed from core material leaking into the mantle billions of years ago. This process may have influenced Earth's habitability by preventing strong chemical layering after its ancient magma ocean phase. The findings, published in Nature Geoscience, link these features to the planet's unique evolution compared to Venus and Mars.
For decades, researchers have been puzzled by two enormous features buried nearly 1,800 miles beneath Earth's surface: large low-shear-velocity provinces (LLSVPs) and ultra-low-velocity zones (ULVZs). LLSVPs are vast masses of hot, dense rock, with one located beneath Africa and another under the Pacific Ocean. ULVZs form thin, partly molten layers clinging to the core in patchy formations. Both significantly slow seismic waves, indicating unusual compositions distinct from the surrounding mantle.
A study led by Yoshinori Miyazaki, an assistant professor at Rutgers University, offers a fresh explanation. Published in Nature Geoscience in 2025, the research integrates seismic data, mineral physics, and geodynamic simulations. It posits that Earth, once covered by a global magma ocean, did not develop expected chemical layers as it cooled. Instead, elements like silicon and magnesium slowly leaked from the core into the mantle over billions of years, mixing materials and disrupting layering.
"These are not random oddities," Miyazaki said. "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."
The model interprets LLSVPs and ULVZs as remnants of a basal magma ocean altered by this core leakage. "What we proposed was that it might be coming from material leaking out from the core," Miyazaki explained. "If you add the core component, it could explain what we see right now."
These deep processes likely shaped Earth's heat release, volcanism, and atmospheric development, contributing to its oceans and life. In contrast, Venus has an atmosphere 100 times thicker than Earth's, mostly carbon dioxide, while Mars has a thin one. "Earth has water, life and a relatively stable atmosphere," Miyazaki noted. "We don't fully understand why that is. But what happens inside a planet... could be a big part of the answer."
The structures may also drive surface volcanism at hotspots like Hawaii and Iceland. Co-author Jie Deng from Princeton University highlighted the study's interdisciplinary approach: "This work is a great example of how combining planetary science, geodynamics and mineral physics can help us solve some of Earth's oldest mysteries."
Miyazaki concluded, "Even with very few clues, we're starting to build a story that makes sense. This study gives us a little more certainty about how Earth evolved, and why it's so special."