Radiogeology

Radiogeology, branch of geology in which scientists measure radioactive elements in rocks, fossils, and other geological specimens to determine their age. The measurement that enables this determination is called half-life—the time it takes one-half of the atoms of a radioactive isotope to decompose and form a different isotope. Radioactivity, found in all living things, is caused by uranium and thorium and their decay products: radioactive potassium, samarium and rubidium, and raciocarbon.