2023-11-20 07:00:05
Deep within the Earth, an intriguing phenomenon is revealed: a thin layer surrounding the molten metal of the outer core. The origin of this layer, called the Eʹ layer, remained misunderstood for decades. However, researchers now believe they have identified the origin of this differentiation: water present on the surface of the Earth.
Image: Argonne National Laboratory / Flickr / CC 2.0
Contrary to what one might think, water does not seep thousands of kilometers through a hole. It is transported by descending tectonic plates and eventually reaches the core after a journey of 2,900 kilometers. This process is slow, but over billions of years, surface water has altered the boundary between the bottom of the mantle and the top of the outer core.
This layer, rich in hydrogen and depleted in silicate, measures a few hundred kilometers thick, which is thin compared to the diameter (In a circle or a sphere, the diameter is a line segment passing through the center…) from the outer core: 6,970 kilometers. According to the water alteration scenario, this modified layer of liquid metal generates silica crystals which migrate into the mantle. This layer is also expected to be less dense and have a lower seismic velocity, characteristics measured by geologists.
“For years, it was believed that the exchange of materials between the Earth’s core and mantle was minimal. However, our recent experiments under high pressure (Pressure is a fundamental physical concept. We can see it as a reported force.. .) reveal another reality. We discovered that when water reaches the core-mantle boundary, it reacts with the silicon in the core, forming silica,” says co-author Dr. Dan Shim of the University higher education whose objective is the…) of Arizona State, in a communiqué.
Illustration of the Earth’s interior revealing water subduction and an ascending magma plume. At the interface where water meets the core, a chemical exchange occurs to form a hydrogen-rich layer at the top of the core. outer core and dense silica at the bottom of the mantle.
Image provided by Yonsei University
“This discovery, in addition to our previous observation of the formation of diamonds from water reacting with carbon in the liquid of iron under extreme pressure, indicates a much more dynamic core-mantle interaction (The word dynamic is often used to designate or qualify what is relative to movement. It…), suggesting substantial exchanges of materials.”
This advance in our understanding of Earth opens new insights into our planet’s internal processes, suggesting a much more extensive global water cycle than previously known. Modification of this core “film” has profound implications for the geochemical cycles linking the surface water cycle with the deep metallic core.
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