Underground ‘sub-continents’ may rewrite geology textbooks

Recent findings from researchers at the Netherlands’ Utrecht University suggest that the long-held belief of a fast-flowing and well-mixed Earth mantle may need revisions. These researchers have discovered two continent-sized geological islands located inside a tectonic plate “graveyard” 1,800 feet below the Earth’s surface, which appear to be “out of tune” with the surrounding environment.

Published in the journal Nature on January 22nd, the study utilizes the tones generated during large earthquakes that cause the Earth to vibrate, allowing seismologists to analyze the planet’s interior through these acoustic signatures. The presence of these underground “super-continents” was first detected over 25 years ago, near the boundary between the mantle and core, prompting further investigation into their existence and characteristics.

The study reveals that these two underground islands, known as Large Low Seismic Velocity Provinces (LLSVPs), show very little damping of seismic waves compared to the surrounding areas. This suggests that the LLSVPs have much larger mineral grain sizes, indicating an ancient age of at least 500 million years. The researchers also found that the LLSVPs are more rigid and resistant to the flow of the Earth’s mantle, challenging previous assumptions about mantle composition and behavior.

These unexpected findings challenge the conventional understanding of a well-mixed and fluid mantle, with implications for Earth’s geological evolution and volcanic activity. By studying the composition and behavior of LLSVPs, researchers can gain insights into the inner workings of the planet and its geological processes.

“The Earth’s mantle is the engine that drives all these phenomena,” said Duess, highlighting the importance of understanding these massive geological formations in unraveling Earth’s mysteries.