This technique exploits the injection of radioisotopes into the atmosphere, which occurred during atmospheric nuclear testing, mainly in the late 1950s and mid 1960s.
Geochronology is the science of determining the age of rocks, fossils, and sediments using signatures inherent in the rocks themselves.
Absolute geochronology can be accomplished through radioactive isotopes, whereas relative geochronology is provided by tools such as palaeomagnetism and stable isotope ratios.
The science of geochronology is the prime tool used in the discipline of chronostratigraphy, which attempts to derive absolute age dates for all fossil assemblages and determine the geologic history of the Earth and extraterrestrial bodies.
By measuring the amount of radioactive decay of a radioactive isotope with a known half-life, geologists can establish the absolute age of the parent material.
APWPs for different continents can be used as a reference for newly obtained poles for the rocks with unknown age.