For decades, geoscientists have been puzzled by two immense, unusual formations hidden deep within Earth’s mantle. These structures—known as large low-shear-velocity provinces (LLSVPs) and ultra-low-velocity zones (ULVZs)—have defied easy explanation. New research from Rutgers University suggests these aren’t random anomalies but rather relics of Earth’s turbulent early history, offering critical clues to why our planet became habitable.
The Enigmatic Structures
LLSVPs are continent-sized masses of dense, hot rock located at the core-mantle boundary, roughly 1,800 miles (2,900 km) beneath the surface. One resides under Africa, while the other sits beneath the Pacific Ocean. ULVZs, in contrast, are thin, molten patches clinging to the core itself, resembling lava puddles. Both dramatically slow down seismic waves, indicating an abnormal composition.
Why this matters: Understanding these structures isn’t just about deep-Earth geology. It’s about unraveling the conditions that allowed Earth to develop liquid water, a breathable atmosphere, and ultimately, life. Venus and Mars, despite being Earth’s planetary neighbors, ended up drastically different; this research suggests core-mantle interactions may be key to that divergence.
A History of Mixing
Early theories predicted that as Earth cooled from its initial molten state, the mantle would separate into distinct chemical layers. However, seismic studies show no such clear stratification. Instead, LLSVPs and ULVZs form irregular piles at the planet’s base. This contradiction led researchers to explore the possibility of mixing between the core and the mantle.
The new model proposes that over billions of years, elements like silicon and magnesium leaked from Earth’s core into the mantle. This infusion prevented the formation of rigid chemical layers, creating the strange composition of the LLSVPs and ULVZs as solidified remnants of a “basal magma ocean” contaminated by core material.
“If you add the core component, it could explain what we see right now,” explains Dr. Yoshinori Miyazaki, lead author of the study published in Nature Geoscience.
Implications for Earth’s Evolution
This discovery has far-reaching implications. Core-mantle interactions may have influenced Earth’s cooling rate, the frequency of volcanic activity, and even the evolution of its atmosphere. The structures may even feed volcanic hotspots like those in Hawaii and Iceland, linking deep-Earth processes to surface phenomena.
The bigger picture: The study demonstrates how combining seismic data, mineral physics, and geodynamic modeling can solve long-standing mysteries. By integrating these fields, scientists are building a clearer picture of Earth’s formative processes.
“The idea that the deep mantle could still carry the chemical memory of early core–mantle interactions opens up new ways to understand Earth’s unique evolution,” says Dr. Jie Deng, a co-author from Princeton University.
Ultimately, this research provides further certainty about why Earth evolved into the unique, habitable planet it is today. The deep mantle isn’t just a geological curiosity; it’s a repository of the planet’s earliest history, waiting to be deciphered.
