The abundances of parent and daughter isotopes in a sample can be measured and used to determine their age. This method is known as radiometric dating. The amount of time that it takes for half of the parent isotope to decay into daughter isotopes is called the half-life of an isotope (Figure 5b).

How does radiometric dating determine absolute age?

Absolute dating is used to determine a precise age of a rock or fossil through radiometric dating methods. This uses radioactive minerals that occur in rocks and fossils almost like a geological clock. These isotopes break down at a constant rate over time through radioactive decay.