A new study published in *Nature Geoscience* offers compelling evidence regarding the origins of massive,continent-sized structures deep within Earth’s mantle. These so-called Large Low-Shear-Velocity Provinces (LLSVPs), located under Africa and the Pacific Ocean, have long been a source of geological mystery, and this research proposes they may be remnants of Earth’s earliest formation-possibly dating back too the planet’s collision with the Mars-sized Theia [[1]].The findings offer a crucial link between the planet’s core, ancient magma oceans, and even the chemical composition of modern volcanic eruptions.
Scientists have discovered massive, continent-sized structures nearly 1,800 miles beneath Earth’s surface, located in previously unknown regions called Large Low-Shear-Velocity Provinces (LLSVPs) under Africa and the Pacific Ocean. The finding offers new insights into the planet’s deep interior and its early formation.
These deep mantle accumulations are hotter, denser, and chemically distinct from surrounding rock, and their origins have puzzled researchers for decades. Understanding the composition and evolution of these structures is crucial for unraveling the history of our planet and the processes that shape its geology.
A new study published in Nature Geoscience proposes that these structures may be remnants from Earth’s earliest geological eras, when the planet was largely covered by a deep magma ocean. The research, led by Yoshinori Miyazaki of Rutgers University-New Brunswick and J. Ding of Princeton University, presents a model linking the deep mantle’s structure to chemical interactions with Earth’s core during its initial formation.
The researchers suggest that Earth’s core wasn’t inert as it cooled, but instead slowly released lighter elements – such as magnesium, oxygen, and silicon – into the base of the magma ocean. This process formed what the team terms a Base-of-Magma-Ocean Compositionally-distinct Reservoir (BECMO).
This chemical separation led to the formation of a heterogeneous layer, rich in silicate minerals like bridgmanite, which subsequently evolved into the LLSVPs. The stability of these dense accumulations over billions of years doesn’t preclude dynamic behavior; they can be affected by mantle convection and potentially rise towards the surface through volcanic plumes.
Computer simulations demonstrate that the new model accurately reproduces the size and shape of the LLSVPs and aligns with patterns observed in volcanic rocks originating from the deep mantle. These rocks offer clues to the planet’s interior composition.
Basaltic volcanic rocks from oceanic islands exhibit unique chemical signatures, including high ratios of helium-3 and anomalies in tungsten and silicon, which have long been a mystery to scientists. The BECMO model proposes that these signatures originated from elements that leaked from the core into the magma ocean and later ascended through surface volcanoes, demonstrating how ancient and modern geological features can be connected.
Researchers emphasize that this discovery not only explains the chemical details but also reframes our understanding of Earth’s deep evolution and the conditions that made our planet habitable. The study provides a comprehensive framework linking seismic data, geodynamic simulations, and geochemical analysis. This integrated approach represents a significant advancement in our understanding of Earth’s internal structure and history.
