They use absolute dating methods, sometimes called numerical dating, to give rocks an actual date, or date range, in numbers of years. This is different to relative dating, which only puts geological events in time order.

What is absolute age rock dating?

Absolute dating methods determine how much time has passed since rocks formed by measuring the radioactive decay of isotopes or the effects of radiation on the crystal structure of minerals. Paleomagnetism measures the ancient orientation of the Earths magnetic field to help determine the age of rocks.