Radiometric dating, often called radioactive dating, is a technique used to determine the age of materials such as rocks. It is based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates. It is the principal source of information about the absolute age of rocks and other geological features, including the age of the Earth itself, and it can be used to date a wide range of natural and man-made materials. The best-known radiometric dating techniques include radiocarbon dating, potassium-argon dating, and uranium-lead dating.
Dating techniques are procedures used by scientists to determine the age of rocks, fossils, or artifacts. Relative dating methods tell only if one sample is older or younger than another; absolute dating methods provide an approximate date in years. The latter have generally been available only since Many absolute dating techniques take advantage of radioactive decay , whereby a radioactive form of an element decays into a non-radioactive product at a regular rate. Others, such as amino acid racimization and cation-ratio dating, are based on chemical changes in the organic or inorganic composition of a sample. In recent years, a few of these methods have come under close scrutiny as scientists strive to develop the most accurate dating techniques possible. Relative dating methods determine whether one sample is older or younger than another.
Radiometric dating calculates an age in years for geologic materials by measuring the presence of a short-life radioactive element, e. The term applies to all methods of age determination based on nuclear decay of naturally occurring radioactive isotopes. Bates and Jackson To determine the ages in years of Earth materials and the timing of geologic events such as exhumation and subduction, geologists utilize the process of radiometric decay. Geologists use these dates to further define the boundaries of the geologic periods shown on the geologic time scale. Radiometric decay occurs when the nucleus of a radioactive atom spontaneously transforms into an atomic nucleus of a different, more stable isotope.