Scientists could have finally found the explanation for a mysterious, crystal-forming layer that surrounds Earth’s core — “leaking water” that trickles down from Earth’s surface and reacts with our planet’s metallic heart.
Within the Nineties, geologists discovered a skinny layer surrounding Earth’s outer core — a swirling ocean of liquid metal that surrounds the solid inner core. The layer, dubbed the E-prime layer, or E’ layer, is greater than 60 miles (100 kilometers) thick — relatively slim compared with other sections of Earth’s interior — and sits around 1,800 miles (2,900 km) beneath Earth’s surface.
Scientists previously theorized that the E’ layer was left behind by ancient iron-rich magma. Other theories posited that it leaked out of the inner core or formed during Earth’s collision with a protoplanet that birthed the moon and left chunks of the infant world inside Earth. But none of those ideas have been widely accepted.
In a brand new study, published Nov. 13 within the journal Nature Geoscience, researchers discovered that the E’ layer was likely created by water that leaks down from Earth’s surface via subducting, or sinking, tectonic plates, then reacts with the outer core’s metallic surface.
If the brand new finding is correct, it means the E’ layer has produced large quantities of silica crystals as a byproduct of this response, which have been fed into the mantle — the huge layer of magma that sits between the outer core and Earth’s outer crust.
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Within the study, researchers conducted a series of laboratory experiments to duplicate how water could react with the outer core under intense pressure. This revealed that the hydrogen from the water replaces the silica inside the liquid metal, which forces the silica out of the metal in the shape of crystals. The E’ layer is due to this fact likely a hydrogen-rich and silica-depleted layer of the outer core, which works against previous assumptions about its composition.
The researchers consider it probably took greater than 1 billion years for the E’ layer to achieve its current thickness, meaning it could possibly be older than the inner core, which solidified around 1 billion years ago.
The brand new finding is one other sign that our current understanding of how the outer core and mantle interact with each other could also be incomplete.
In September 2022, the identical research team discovered that leaking water could possibly be reacting with large reservoirs of carbon within the outer core to create gigantic diamond factories near the core-mantle boundary.
“For years, it has been believed that material exchange between Earth’s core and mantle is small,” study co-author Dan Shim, a geoscientist at Arizona State University, said in a statement. But these discoveries “point to a much more dynamic core-mantle interaction, suggesting substantial material exchange.”