They reveal the complex reactions caused by the liquid when it descends to almost 3,000 kilometers below the surface
A few decades ago, seismologists who took Images of the planet’s deepest interior identified a thin layer, just over a few hundred kilometers thick, until then unknown. The origin of this layer, known as primary layer E, has remained a mystery until now. However, that enigma has been largely solved and has provided surprises for scientists.
An international team of researchers, including Arizona State University scientists Dan Shim, Taehyun Kim and Joseph O’Rourke of the School of Earth and Space Exploration, has discovered that The water existing on the surface of the Earth can penetrate to surprising depths into the planet, to the point of altering the composition of the outermost region of the metallic liquid core and creating a thin and differentiated layer.
The research, which has been published in Nature Geosciencedetails that over billions of years, surface water has been transported to the deepest depths of the Earth through descending tectonic plates (subduction), which go deep into the interior of the planet.
Water reservoir in Spain
| efe
Interaction with the earth’s core
Upon reaching the boundary between the core and the mantle, About 2,900 kilometers below the surface, this water triggers a deep chemical interaction that alters the structure of the core.
Together with Yong Jae Lee of Yonsei University in South Korea, Shim and his team have shown through high-pressure experiments that subducted water chemically reacts with core materials. This reaction gives rise to a layer rich in hydrogen and depleted in silicon, altering the upper region of the outer core into a film-like structure. Furthermore, this reaction generates silica crystals that rise until they integrate into the mantle.
The study authors believe that this modified liquid metal layer will be less dense, with reduced seismic velocities, consistent with the anomalous features that seismologists have detected and mapped.
“For years, the exchange of material between the Earth’s core and mantle was thought to be small. However, our recent high-pressure experiments reveal a different story. “We found that when water reaches the boundary between the core and the mantle, it reacts with the silicon in the core, forming silica,” Shim said.
Interior of the Earth
| Agencies
“This discovery, along with our previous observation of diamonds forming from water reacting with carbon in liquid iron under extreme pressure, points to a much more dynamic core-mantle interaction than previously thought, suggesting substantial exchange of material“he added.
This discovery sheds light on the complex and still very unknown internal processes of the Earth, and demonstrate a broader global water cycle than previously recognized. The altered ‘film’ or layer of the core has profound implications for the geochemical cycles that connect the surface water cycle to the deep metallic core.
This study was conducted by an international team of geoscientists using advanced experimental techniques at the Argonne National Laboratory’s Advanced Photon Source and PETRA III at the Deutsches Elektronen-Synchrotron in Germany to replicate the extreme conditions at the core-mantle boundary.
Reference study: https://www.nature.com/articles/s41561-023-01324-x
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