Because of their unique decay rates, different elements are used for dating different age ranges. For example, the decay of potassium-40 to argon-40 is used to date rocks older than 20,000 years, and the decay of uranium-238 to lead-206 is used for rocks older than 1 million years.

How are radioactive elements used to date rocks?

Some minerals in rocks and organic matter (e.g., wood, bones, and shells) can contain radioactive isotopes. 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.

What element is used to date old rocks?

For old rocks, a radioactive element with a very long half-life is needed. One such element is samarium, which is present in minuscule amounts in most rocks and minerals. Radio-active samarium transforms to neodymium with a half-life of 106 billion years.

What is the importance of dating in rocks?

Dynamic Earth - Dating rocks. Gaining estimates of ages of rocks is crucial for establishing not only the history of geological events but also for determining the rates of geological processes. It is possible to establish the relative order of events in some rocks.