Water from the Earth’s surface can find its way deep into the planet, and a new study explains how water replaces the outermost part of the metallic liquid core. This finding could explain the presence of a thin layer of material inside the planet that has puzzled geologists for decades.
The Earth’s crust consists of tectonic plates that rub and slide under each other; Over billions of years, these subduction zones transported water into the lower mantle.
When this water reaches the core-mantle boundary, about 2,900 kilometers (1,800 miles) below the surface, it begins a strong chemical interaction. A team from South Korea, the United States and Germany showed that it forms a hydrogen-rich upper core and sends silica into the lower mantle.
“For many years, the exchange of material between the Earth’s core and mantle was thought to be small,” says Dan Shim, a materials scientist at Arizona State University.
“But our recent high-pressure experiments tell a different story. We found that when water reaches the core-mantle interface, it reacts with the silicon in the core to form silica.”
The outer core’s mixture of iron and nickel plays an important role in creating Earth’s magnetic field, which protects life on the planet from solar winds and radiation. Therefore, it is important to understand how the Earth’s interior functions and how it has evolved over time.
The boundary between the Earth’s core and mantle changes quite sharply from silicate to metal, and little is known about the chemical changes. Decades ago, researchers recording seismic waves in the Earth’s sticky interior documented a thin layer just over a few hundred kilometers thick, but until now no one knew where this so-called “E prime” layer came from.
“We hypothesize that such chemical exchange between the core and mantle during years of deep-water transport may have contributed to the formation of the putative E main layer,” the team writes.
Seismologists discovered some unusual features that suggest this altered layer of liquid metal would be less dense and have a lower seismic velocity. These differences in density are thought to be related to different concentrations of light elements such as hydrogen or silicon.
However, an increase in the concentration of a light element will increase the velocity and decrease the density, making it difficult to reconcile seismic observations with the dynamic stability of the main layer E. decreased concentration of another has been suggested as a possible explanation. However, scientists were unaware of such a change process.
The team used laser-heated diamond anvil cells to simulate the pressure and temperature conditions at the core-mantle interface. They showed that water entering the Earth’s core can chemically react with materials there, converting the outer core into a hydrogen-rich film and disperse silica crystals that rise and merge with the mantle.
The layer of hydrogen-rich, silicon-poor material that forms at the top of the core will have lower density and slower velocity, consistent with seismic wave observations. The altered core film could have significant effects on the deep water cycle, and the team says their results point to a more complex global water cycle than we thought.
“This discovery, together with our previous observations of diamond formation from water reacting with carbon in liquid iron under extreme pressure,” says Shim, “points to a much more dynamic interaction between the core and mantle, indicating a significant change.” materials.” Source
Source: Port Altele
