Remnants of the planet’s original crust have been unearthed in Quebec, according to a study in Science. The remnants date back about 4.3 billion years and were found embedded in younger granite near Hudson Bay, reports Live Science. While the granite itself is only 2.7 billion years old, the researchers analyzed it for chemical signals of a "parent rock" that had previously melted and been recycled into another form. Popular Mechanics reports that the team used a new and rarely used scientific technique that tracks the decay of a specific isotope, and were thrilled by what they found.
"I think that it's a piece of the original crust," says lead researcher Jonathan O'Neil of the University of Ottawa. "It was cooked, but I think it's still very close to what it used to be." The larger granite formation is part of Earth’s second crust, but the geologists believe the parent rock is basalt, or oceanic crust. According to O’Neil, modern oceanic crust usually stays above the surface for 200 million years. It is then forced back into the mantle, where it melts partially. The parent rock the team found in Hudson Bay’s granite, on the other hand, remained at the surface for more than a billion years before being recycled. Atlas Obscura calls it "the most direct evidence ever found of how the crust on this planet was composed when it first formed." (Scientists say they've found an eighth continent.)
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