The oldest known rock
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
Topic: Earth Science
Subtopic: Geologic Time
Keywords: Gneiss, Geology, Earth (Planet)--Origin, Zircon, Earth (Planet)--Age