Briefing Sheet Session 2: The age of the Earth
Scientists have used many different methods to calculate the age of the Earth. They use layers in trees and ice cores back to over 10,000 years and 200,000 years. Changes in the Earth's magnetic field are recorded in rocks, and can be used to date them over several million years, while radiometric dating using decaying isotopes can be used to establish that the age of the earth is about 4.5 billion years old.