In 2014, researchers published a study in the journal Nature Geoscience showing that parts of Australia's Jack Hills were a jaw-dropping 4.4 billion years old. To come to this discovery, the team shaved away tiny zircon crystals—we're talking no larger than a dust mite—from rocks they found in the Jack Hills. They contained radioactive atoms of lead dating back from when the crystals solidified from lava. The atoms started out as radioactive uranium, but over billions of years they shed nuclear particles to become lead. By dating the lead atoms directly, the researchers found that the crystals were probably around 4.4 billion years old.
Where's the oldest place on Earth? Because plate tectonics constantly recycles our planet's crust, that's a difficult question to answer. Even so, scientists think they've done it: crystals discovered in the Jack Hills of western Australia appear to put them on the oldest continental crust on Earth.
How Old Is That?
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Key Facts In This Video
Earth's outermost layer is constantly renewing itself, making the planet appear "younger." 00:21
The mineral zircon is durable, like quartz, but contains small traces of radioactive uranium. 01:31
Uranium-lead dating of zircon tells us that the Earth is at least 4.4 billion years old. 02:33