Status: 05.12.2023, 16:32 PM
By: Tanja Banner
The earth is built up in different layers. From the outside to the inside: the Earth's crust, (upper and lower) mantle, outer core and inner core. (Symbolic image) © IMAGO/Zoonar.com/Cigdem Simsek
An international team of researchers presents a surprising theory of the formation of the Earth's "e prime" layer. Water played a crucial role in this.
Tempe – A previously mysterious layer in the Earth's interior, discovered by scientists in the 1990s and dubbed "e prime," has been unlocked from a secret. An international research team, led by Dan Shim from Arizona State University, has now presented a plausible explanation for the formation of this layer, which is just over 100 kilometres thick, in the renowned journal Nature Geoscience. According to this, water from the Earth's surface played a decisive role in the formation of the thin layer of Earth.
In high-pressure experiments, the scientists were able to prove that water that penetrates the Earth's mantle undergoes chemical reactions with the materials of the Earth's core. According to the researchers, this interaction results in a hydrogen-rich but silicon-poor layer that converts the uppermost outer region of the Earth's core into a film-like structure – the so-called "e prime" layer. In addition, silicon dioxide crystals are formed, which rise and blend into the Earth's mantle.
Earth's mantle is apparently more permeable than previously thought
The researchers assume that over the course of billions of years, surface water has been transported deep into the Earth through the process of subduction – a phenomenon of plate tectonics in which tectonic plates meet and one dives under the other. When it reached the boundary between the Earth's core and mantle at a depth of about 2900 kilometres, the water triggered the chemical reaction.
Dan Shim explains in a statement: "For years, it has been assumed that the exchange of material between the Earth's core and the mantle is low, but our latest high-pressure experiments show a different picture." He adds: "We found that when water reaches the core-mantle boundary, it reacts with silicon in the core to form silica."
This discovery leads the scientist to conclude that there is "a far more dynamic interaction between the core and the mantle, suggesting a significant exchange of material." So it seems that the Earth's mantle is more permeable than research has previously assumed. (tab)
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