Earth’s Oldest Crust Dates to 4.4 Billion Years Ago

National Geographic reports that Australia holds the oldest continental crust on Earth, hills some 4.4 billion years old. For more than a decade, geoscientists have debated whether the iron-rich Jack Hills of western Australia represent the oldest rocks on Earth. The new findings rely on atom-scale analyses of tiny crystals in rocks that solidified from lava there eons ago. (See also: “Oldest Rocks on Earth Discovered?“). “This confirms our view of how the Earth cooled and became habitable,” said study leader John Valley of the University of Wisconsin-Madison, in a statement. “This may also help us understand how other habitable planets would form.”

Earth itself is a bit more than 4.5 billion years old, and the researchers hope the new finding offers insights into the formation of the moon and the first continents. The Jack Hills rocks formed only about 160 million years after the formation of the solar system—which is surprisingly early. The zircon crystals analysed by the researchers in the Nature Geoscience journal study point to Earth’s earliest crust cooling from a planet-wide lava ocean. The lava ocean was likely born in the astronomical collision that created the moon.