Illustration of the Earth’s interior showing the existence of a new layer at the top of the outer core. Water contained in the tectonic plate subducting to the boundary between the core and the mantle causes an element exchange reaction with components of the outer core, forming a hydrogen-rich layer at the top of the outer core and a high-density silica layer at the bottom of the mantle. It shows that it is formed. (Image from Yonsei University, made by Nanosphere)
A research team led by Professor Lee Yong-jae of the Department of Earth System Science at Yonsei University (High-Pressure Mineral Physics and Chemistry Research Center) announced research results showing that water moving deep into the mantle can react with iron, the main component of the core, to form a hydrogen-rich layer at the top of the Earth’s outer core.
This study, conducted jointly with Professor Shim Sang-heon’s research team at Arizona State University, is the first to explain the formation mechanism of the seismic wave low-velocity layer, which was expected to exist at the top of the core. It has been shown that the diverse and complex reactions and structures that occur on the Earth’s surface can also occur in the deepest part of the Earth, at the boundary between the core and the mantle.
The Earth’s core is mainly composed of iron, but it also contains some elements lighter than iron, such as silicon, oxygen, sulfur, and hydrogen, which lowers the overall density of the core and maintains convection in the core, which is key to forming the Earth’s magnetic field, for a long time. In particular, the liquid outer core comes into direct contact with the rocky mantle, forming a boundary at a depth of about 2,900 km underground.
In the past, exchange of materials was thought to be limited at the boundary between the core and the mantle, but recent research has shown that water on the surface can be partially contained in minerals from subducting tectonic plates and transported deep into the mantle. Accordingly, Professor Lee Yong-jae’s research team predicted that if water reaches the interface between the core and the mantle, there will be an increased possibility that the core’s constituent materials will be affected, just as rocks are weathered by water on the surface.
To observe the reaction between iron and water that occurs at the boundary between the core and the mantle, the research team used a small high-pressure generator called a Diamond Anvil Cell and an infrared laser to create pressure conditions of over 1.3 million times atmospheric pressure and temperature conditions of over 4,000 degrees. , the reaction process was observed through a very small and bright X-ray beam created in a synchronized light accelerator.
Under these experimental conditions, the hydrogen component of water combined with iron, and the silicon component that previously existed with iron reacted with the oxygen component of water and was converted into high-density silica. This exchange reaction results in the formation of a light hydrogen-rich uppermost layer of the outer core and a denser silica-rich lowermost layer of the mantle.
In this study, we explain the mechanism of the seismic low-velocity layer that forms at the top of the outer core, assuming that about 1% of the subducted water reaches the core-mantle boundary in the form of stable hydrous minerals and that this process continued for about 2.5 billion years. I did. Professor Shim Sang-heon of Arizona State University, who participated in the joint research, said, “As a result of these accumulated element exchange reactions, there may currently exist a stable layer hundreds of kilometers thick at the top of the outer core, storing approximately one trillion tons of hydrogen.”
Professor Lee Yong-jae of Yonsei University said, “The Earth has constantly changed its surface from the past to the present through the formation and movement of tectonic plates.” He added, “This study shows that these dynamic movements and changes of the Earth are not only at the surface but also at the deepest boundary of the Earth. “It suggests that this has been going on in parallel,” he said, explaining the significance of this study.
The study said that high-temperature and high-pressure
The research results were published on November 13 (local time) in the geoscience journal ‘Nature Geoscience’.
논문명 : A hydrogen-enriched layer in the topmost outer core sourced from deeply subducted water
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