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Geochemists solve mystery of Earth’s vanishing crust

Scientists examined hundreds of samples taken along the global ridges that contain recycled ancient oceanic crust in variable amounts. “Depleted” segments of the ridge received lower than “normal” amounts of recycled crust, while “enriched” segments contain a larger proportion of recycled crust. Credit: Caroline McNiel/National MagLab Thank goodness for the Earth’s crust: It is, after all, that solid, outermost layer of our planet that supports everything above it.

But much of what happens below that layer remains a mystery, including the fate of sections of crust that vanish back into the Earth. Now, a team of geochemists based at the Florida State University-headquartered National High Magnetic Field Laboratory has uncovered key clues about where those rocks have been hiding.

The researchers provided fresh evidence that, while most of the Earth’s crust is relatively new, a small percentage is actually made up of ancient chunks that had sunk long ago back into the mantle then later resurfaced. They also found, based on the amount of that “recycled” crust, that the planet has been churning out crust consistently since its formation 4.5 billion years ago—a picture that contradicts prevailing theories.

Their research is published in the journal Science Advances .

“Like salmon returning to their […]

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