A new study has revealed that the interior of Earth’s mantle is not as layered as previously thought. Seismologists used a high-resolution method called full-waveform inversion to map the Earth’s internal structures, and what they found was surprising.
The mantle, which makes up around 84% of Earth’s volume, is primarily composed of silicate minerals rich in iron and magnesium. It behaves like a thick, slow-flowing fluid over long periods of time, driving the movement of tectonic plates on Earth’s surface.
However, researchers discovered pockets of material that appear to be leftover plate fragments in areas with no known history of subduction. These anomalies were found throughout the Earth’s interior and challenged assumptions about where old tectonic plate remnants might reside.
The discovery was made using a new approach that examines all types of seismic waves produced by earthquakes, rather than focusing on only one type. This method revealed large slabs below oceans and continental interiors that lack a clear history of plate collisions.
One of the biggest surprises was in a zone under the western Pacific, where there is no reason for old plate fragments to be present according to current plate tectonic timelines.
The study’s lead author, Thomas Schouten, said that the new model reveals anomalies throughout the Earth’s interior, but the exact materials or plate fragments responsible for these patterns remain unclear. The discovery suggests a more diverse range of compositions in the Earth’s mantle than previously understood.
Researchers are now facing questions about the origin and nature of these structures. Some suggest they may be ancient, silica-rich pockets left over from the early mantle, while others propose that they might be iron-rich accumulations that have drifted over billions of years.
The study’s findings have significant implications for our understanding of plate tectonics and the movement of heat through the planet. The discovery also highlights the importance of combining different methods to gain a clearer picture of the Earth’s internal structures.
Source: https://www.earth.com/news/sunken-worlds-discovered-under-the-pacific-ocean-in-earths-mantle