New research sheds light on how water from Earth’s surface makes its way deep into the planet and alters the outermost layer of the metallic liquid core, providing crucial insight into a long-standing geological mystery.
Over billions of years, water transported through Earth’s crust has reached the lower mantle, about 2,900 kilometers (1,800 miles) below the surface, where it initiates a powerful chemical reaction. This process leads to the creation of a top core layer rich in hydrogen and the dispersion of silica to the lower mantle.
Despite previous beliefs about minimal material exchange between Earth’s core and mantle, recent high-pressure experiments have revealed a different story. A team of researchers from South Korea, the US, and Germany have demonstrated the profound impact of water reaching the core-mantle boundary, highlighting how it reacts with silicon in the core to form silica.
The outer core, consisting of iron and nickel, is integral to generating Earth’s magnetic field. A deeper understanding of the mechanisms at work within Earth’s core is essential to comprehending its evolution and the protective role it plays in shielding the planet from solar winds and radiation.
Unveiling the chemical exchanges at Earth’s core-mantle boundary presents a significant challenge, but recent discoveries may offer critical insights. The occurrence of a thin ‘E prime’ layer, identified decades ago through seismic observations, has perplexed scientists, but the team of researchers now proposes that the deep transport of water could have contributed to its formation.
In order to simulate the pressure-temperature conditions at the core-mantle boundary, the research team utilized laser-heated diamond-anvil cells. Their experiments demonstrated how water subducted into Earth’s core leads to a chemical transformation, resulting in the outer core becoming hydrogen-rich and the dispersion of silica crystals into the mantle.
The formation of a hydrogen-rich and silicon-poor layer at the top of the core would align with seismic wave observations, providing valuable validation for the research findings. Furthermore, this newly identified layer could have significant implications for Earth’s deep water cycle, indicating a more complex process than previously understood.
“This discovery, along with our previous observation of diamonds forming from water reacting with carbon in iron liquid under extreme pressure, points to a far more dynamic core-mantle interaction, suggesting substantial material exchange,” says Dan Shim of Arizona State University.
The study has been documented in Nature Geoscience, offering valuable insights into Earth’s internal processes and their broader implications.
