Ancient Magma Ocean Beneath Earth's Mantle May Still Exist, New Study Suggests

A groundbreaking study published in Nature on March 26 claims that a vast ocean of magma may still reside deep within Earth’s mantle — a remnant of our planet’s earliest formation nearly 4.4 billion years ago. The research offers new insights into Earth’s internal structure, proposing that this ancient molten layer continues to influence tectonic activity and thermal dynamics today.

A Primordial Magma Ocean Near the Core

Led by Assistant Professor Charles-Édouard Boukaré from York University, Toronto, alongside researchers from prominent French institutions, the study presents compelling evidence of a basal magma ocean at the boundary between Earth’s mantle and core. The team’s model integrates geochemical and seismic data, highlighting how early crystallization processes could have resulted in a persistent molten layer deep within the planet.

The formation, the researchers argue, would have occurred regardless of whether Earth’s solidification began from the core outward or from the surface inward. High pressures and temperatures deep underground would cause dense, iron oxide-rich materials to sink and remelt, creating a long-lasting reservoir of molten rock.

Connection to Present-Day Mantle Anomalies

The presence of this ancient magma ocean could help explain seismic anomalies observed at the mantle-core boundary, particularly the Large Low-Velocity Provinces (LLVPs). These anomalies have puzzled geologists for decades, as they represent vast regions where seismic waves slow down significantly — suggesting the presence of hot, possibly molten material.

Boukaré noted in a statement to Live Science that this persistent melt layer might act as a thermal barrier between the mantle and the core, thereby influencing tectonic plate activity, mantle convection, and even volcanism. “There is a memory,” Boukaré explained, referencing how Earth’s internal structure reflects ancient events that still shape geological processes today.

Implications for Planetary Science

The findings also extend beyond Earth. Boukaré and his team suggest that such basal magma oceans may not be unique to our planet. The researchers plan to apply their model to other rocky planets in the solar system to explore whether similar processes might have occurred during their formation.

If validated, this could revolutionize our understanding of planetary evolution, shedding light on how internal heat and mantle dynamics have evolved across different celestial bodies.

Key Takeaways

• Basal magma ocean formation began ~4.4 billion years ago, possibly influencing Earth’s tectonic and thermal behavior today.

• The model explains mantle anomalies like LLVPs, which are detected via seismic imaging.

• The magma ocean results from iron-rich solids sinking and remelting under extreme pressure and temperature conditions.

• This ancient layer may act as a thermal and tectonic buffer, shaping geological processes.

• Researchers aim to explore similar formation models on other rocky planets, suggesting this phenomenon might be more widespread.