Geologists Reveal That Surface Water Is Transforming Earth's Outer Core

The chemistry at the center of our planet has eluded scientists for centuries. But new research from Arizona State University has shone a light on these mysterious internal processes, suggesting the Earth's outer core may be more dynamic than we once thought.

Our planet consists of four distinct layers: the inner and outer core, the mantle and, on the surface, the crust. The thickest layer—the mantle—begins at about 18.6 miles beneath the surface and stretches out for 1,865 miles, making up 84 percent of the Earth's volume, according to National Geographic. It is mostly made of silicates—a range of rocks that contain silicon and oxygen within their structure.

Between the mantle and the outer core, nearly 1,900 miles deep, exists a thin layer known as the E prime layer, which marks the boundary between the silicate rocks of the mantle and the molten metal in the Earth's core.

"For years, it has been believed that material exchange between Earth's core and mantle is small," Dan Shim, an Earth sciences professor at Arizona State University, said in a statement. "Yet, our recent high-pressure experiments reveal a different story."

Together with colleagues from Yonsei University in South Korea, the Advanced Photon Source at the Argonne National Laboratory in Illinois and the Deutsches Elektronen-Synchrotron in Germany, Shim and his team studied the behavior of two key components of the mantle and outer core under extreme temperature and pressure to mimic the conditions of the core-mantle boundary.

The results were published in the journal Nature Geoscience on November 13.

"We found that when water reaches the core-mantle boundary, it reacts with silicon in the core, forming silica," Shim said. "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."

These findings represent an important advance in our understanding of Earth's internal processes and suggest that the global water cycle goes much deeper than was once thought.

The results come just months after physicists at the University of Texas at Austin found what they described as the "holy grail" of geophysics, recreating a miniature model of the dynamics of the iron atoms in Earth's inner core.

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