The oldest known rock

  • Exhibition Text

    • By dating the zircons embedded within the Acasta gneiss, geologists have determined its age to be 3.96 billion years. This rock’s composition establishes it as part of a continent, indicating that continents existed nearly four billion years ago.

      Donated by Royal Ontario Museum, Toronto, Canada

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  • For Educators

    • Topic: Earth Science

      Subtopic: Geologic Time

      Keywords: Gneiss, Geology, Earth (Planet)--Origin, Zircon, Earth (Planet)--Age

      Audience: General