A few decades ago, seismologists exploring the deep recesses of our planet Earth stumbled upon a puzzling phenomenon—a slender layer just a few hundred kilometers thick, known as the E prime layer. For years, its origin remained shrouded in mystery. However, a recent breakthrough by an international team, including researchers from Arizona State University, has brought clarity to this long-standing puzzle.
EARTH; ALTERING COMPOSITION
Published in Nature Geoscience, the research sheds light on the E prime layer, revealing that water from Earth’s surface can penetrate deep into the planet. This infiltration alters the composition of the outermost region of the metallic liquid core, forming a distinct, thin layer. The study, led by scientists Dan Shim, Taehyun Kim, and Joseph O’Rourke, demonstrates that over billions of years, surface water transported by descending tectonic plates undergoes a profound chemical interaction upon reaching the core-mantle boundary.
Through high-pressure experiments, the team, including Yong Jae Lee of Yonsei University, showcased that subducted water chemically reacts with core materials. This reaction gives rise to a hydrogen-rich, silicon-depleted layer, transforming the topmost outer core region into a film-like structure. Moreover, silica crystals generated in the process ascend and integrate into the mantle. This modified liquid metallic layer is anticipated to be less dense, aligning with anomalous seismic characteristics mapped by seismologists.
A DIFFERENT STORY
The discovery challenges previous beliefs about the limited material exchange between Earth’s core and mantle. Dan Shim emphasizes, “For years, it has been believed that material exchange between Earth’s core and mantle is small. Yet, our recent high-pressure experiments reveal a different story.” This revelation, coupled with the team’s earlier observation of diamonds forming from water reacting with carbon in iron liquid under extreme pressure, points to a more dynamic core-mantle interaction, suggesting substantial material exchange.
Beyond its scientific significance, this finding advances our understanding of Earth’s internal processes, indicating a more extensive global water cycle than previously recognized. The altered “film” of the core holds profound implications for the geochemical cycles connecting the surface-water cycle with the deep metallic core.
Conducted by an international team of geoscientists, the study utilized advanced experimental techniques at the Advanced Photon Source of Argonne National Lab and PETRA III of Deutsches Elektronen-Synchrotron in Germany to replicate the extreme conditions at the core-mantle boundary. This research marks a crucial step forward in unraveling the secrets hidden within Earth’s depths.