The most widely used radioactive cosmogenic isotope is carbon of mass 14 (14C), which provides a method of dating events that have occurred over roughly the past 60,000 years. This time spans the historic record and a significant part of the prehistoric record of humans.

What are uses of isotopic dating?

Radioactive dating is a method of dating rocks and minerals using radioactive isotopes. This method is useful for igneous and metamorphic rocks, which cannot be dated by the stratigraphic correlation method used for sedimentary rocks. Over 300 naturally-occurring isotopes are known.