The rock cycle explains that geologic processes on Earth continually form and re-form rock layers. This causes rocks on Earth to have ages varying from days to billions of years old. It is these same rocks that provide special clues to Earth’s history. While it is possible to find the precise age of a rock in a laboratory, most scientists use a method called relative dating to get an estimated age. Relative dating enables geologists to assign ages to rock layers without using numbers, and it unlocks secrets to Earth’s prehistoric past.
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