Underneath The Pacific Ocean, There Are Sunken Worlds In The Earth’s Mantle
Under the Pacific Ocean, hidden material was discovered in Earth’s mantle. So we have sunken, ancient worlds down there, and they’re full of surprises.
Experts depend on specific types of earthquake waves to learn about Earth’s subsurface, but now, another technique is revealing more details than ever.
The mantle is the thick layer of rock between the planet’s crust and core. It is about 1,800 miles deep and is mainly composed of silicate minerals rich in magnesium and iron. For the most part, the mantle is solid, but over long periods of time, it acts like a thick, slow-moving fluid.
The flow of the fluid is what prompts the movement of tectonic plates on the surface of the Earth, leading to earthquakes, volcanic eruptions, and the shifting of land masses. The heat from the Earth’s core causes convection currents in the mantle.
In this process, hot material rises, cools down as it nears the crust, and then sinks again, creating a continuous cycle and helping to shape the Earth’s surface.
The discovery was made using a high-resolution method known as full-waveform inversion. This approach is used to interpret all kinds of seismic waves produced by earthquakes, allowing scientists to construct a more accurate model of the planet’s internal structures.
After applying the technique to the lower mantle, researchers noticed what appeared to be leftover plate fragments in areas that did not have a known history of subduction. They were surprised by how common these hidden materials can be.
The research was led by a team from the Geological Institute of ETH Zurich and the California Institute of Technology. Their work brought about new ideas of where the remnants of old tectonic plates might reside in Earth.
The research team measured the length of time it took for seismic waves to reach various seismic stations around the globe in order to uncover details about rock density and stiffness.
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By looking over all available seismic wave data, they were able to identify never-before-seen shapes and densities within Earth’s lower mantle.
Plates have formed, shifted, and sunk back into Earth’s interior throughout hundreds of millions of years, clustering under regions where they slide beneath one another.
It was a shock for researchers to see new images that depicted large slabs below oceans and continental interiors that did not contain a history of plate collisions. That could change scientific understanding of the evolution of plates and where they end up.
A zone under the western Pacific contained old plate fragments, even though there was no reason for them to be there, according to plate tectonic timelines. The materials may not be plate fragments after all.
Some scientists think they may be ancient pockets rich in silica that were leftover from the early mantle. Others have suggested they may be iron-rich structures that drifted to the area over the course of billions of years.
The exact plate fragments or materials responsible for the patterns are still unclear. Their existence suggests that the Earth’s mantle is more complex than previously believed.
“With the new high-resolution model, we can see such anomalies everywhere in the Earth’s mantle. But we don’t know exactly what they are or what material is creating the patterns we have uncovered,” Thomas Schouten, first author, said in a press release.
The study was published in Scientific Reports.
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