To establish the age of a rock or a fossil, researchers use some type of clock to determine the date it was formed. Geologists commonly use radiometric dating methods, based on the natural radioactive decay of certain elements such as potassium and carbon, as reliable clocks to date ancient events.

Why do geologists use radioactive dating?

Geologists use radiometric dating to estimate how long ago rocks formed, and to infer the ages of fossils contained within those rocks. The universe is full of naturally occurring radioactive elements. Radioactive atoms are inherently unstable; over time, radioactive parent atoms decay into stable daughter atoms.

How is radioactivity used in geology?

The radioac- tivity of rocks, minerals, water, and organic mat- ter is widely used in dating geological and ar- cheological materials as well as groundwater. Energy liberated during radioactive decay is now considered to be one of the main sources of heat within the Earth.