Recent findings from researchers at Utrecht University in the Netherlands challenge the long-held belief that the Earth’s mantle is fast flowing and well-mixed. The evidence comes from two sunken geological islands, the size of continents, located 1,800 feet below the Earth’s surface within a tectonic plate “graveyard.”
Published in the journal Nature, the study uses tones generated during large earthquakes to analyze the Earth’s interior. These tones, created as the Earth vibrates like a giant bell, provide insights into the planet’s structure and anomalies such as regions that are out of tune or have dampened volume.
About 25 years ago, researchers discovered underground “super-continents” beneath Africa and the Pacific Ocean, referred to as Large Low Seismic Velocity Provinces (LLSVPs). These formations, situated near the boundary between the mantle and core, raised questions about their age and permanence.
The study reveals that the LLSVPs exhibit minimal damping of seismic waves, indicating a hotter temperature compared to their surroundings. Contrary to expectations, the acoustic tones in the LLSVPs are very loud, while the cold slab graveyard shows significant damping, leading to softer tones.
Further analysis of the LLSVPs’ mineral composition, particularly grain sizes, suggests that larger grains contribute to the formations’ ancient age—potentially over 500 million years old. These rigid grains resist mantle convection, highlighting the significance of their interaction with the Earth’s interior.
The implications of these discoveries extend beyond seismology, offering insights into Earth’s evolution, volcanic activity, and mountain formation. Understanding the dynamics of LLSVPs sheds light on the Earth’s internal processes and geological phenomena.
As seismologist Arwen Deuss explains, the Earth’s mantle plays a crucial role in driving various phenomena, such as mantle plumes that originate at the edges of LLSVPs and contribute to volcanic activity.
