Age of Earth’s crust confirmed

zircon from Jack Hills, Australia

Scientists have confirmed a contentious date of the Earth’s crust by tracking how decaying isotopes travel through zircon (shown), the Earth’s oldest mineral.

John Valley/Univ. of Wisconsin

Guest post by Beth Mole

By spying how atoms flow through zircon — the planet’s oldest mineral — researchers have backed one of the oldest dates recorded for Earth’s crust, between 4.368 and 4.380 billion years old.

Scientists date the crust using the proportion of uranium isotopes that have decayed to lead isotopes in zircon. But lead isotopes can move through tiny faults in the mineral’s structure, which some scientists have suggested could throw off the ratios and yield fallacious ages.

By tracking individual atoms in zircon, researchers report February 23 in Nature Geoscience that such lead relocations were mere nanometer distances, not far enough to influence micrometer-scale dating techniques.

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