The abundances of parent and daughter isotopes in a sample can be measured and used to determine their age.
Over time, the radioactive isotope of potassium decays slowly into stable argon, which accumulates in the mineral.
What Is Cave Popcorn?
Evolutionary Anthropology 6:
Description: As these changes have occurred, organisms have evolved, and remnants of some have been preserved as fossils. The principles of stratigraphy help us understand the relative age of rock layers.