Radiometric dating (often called radioactive dating) is a technique used to date materials such as rocks or carbon, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates.The use of radiometric dating was first published in 1907 by Bertram Boltwood and is now the principal source of information about the absolute age of rocks and other geological features, including the age of the Earth itself, and can be used to date a wide range of natural and man-made materials.Decay curve of a radioactive element with a half-life equal to one time unit.
At any moment, the ratio between them is a measure of the time elapsed, as long as the system remains closed.
As magma cools, radioactive parent isotopes are separated from previously formed daughter isotopes by the crystallization process.
Ideally, the mineral crystals in igneous rocks form a closed system--nothing leaves or enters the crystal once it is formed.
As radioactive Parent atoms decay to stable daughter atoms (as uranium decays to lead) each disintegration results in one more atom of the daughter than was initially present and one less atom of the parent.
The probability of a parent atom decaying in a fixed period of time is always the same for all atoms of that type regardless of temperature, pressure, or chemical conditions. The time required for one-half of any original number of parent atoms to decay is the half-life, which is related to the decay constant by a simple mathematical formula.