Most absolute dates for rocks are obtained with radiometric methods. These use radioactive minerals in rocks as geological clocks. The atoms of some chemical elements have different forms, called isotopes. Each original isotope, called the parent, gradually decays to form a new isotope, called the daughter.

What is a geological method of absolute dating?

Absolute dating is the process of determining an age on a specified chronology in archaeology and geology. Some scientists prefer the terms chronometric or calendar dating, as use of the word absolute implies an unwarranted certainty of accuracy.