All our evidence for changes in the Earth comes from looking at rocks. Folds and fossils in sedimentary rocks, radioactive dating and the weathering of ancient craters show that the oldest rocks are about 4000 million years old. That means the Earth must be at least as old as this. It is from being able to understand the age of the rocks on the earth that we know how old the earth itself is. The technique of dating the age of rocks is known as radiometric dating:
https://en.wikipedia.org/wiki/Radiometric_dating.
For specifics of how the rocks are used to evaluate the age of the earth, please see this article:
For specifics of how the rocks are used to evaluate the age of the earth, please see this article:
https://en.wikipedia.org/wiki/Age_of_the_Earth, which gives much more detail on the geological calculations used in this science.
You might also be interested in this recent data from National Geographic:
which finds the Earth to be 4.4 Billion years old (4400 000 000).
Kind regards,
Victoria
Public Information Volunteer
David Suzuki Foundation
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www.davidsuzuki.org
