One of the most widely used is potassium–argon dating (K–Ar dating).
Potassium-40 is a radioactive isotope of potassium that decays into argon-40.
The relatively short half-life of carbon-14, 5,730 years, makes the reliable only up to about 50,000 years.
The technique often cannot pinpoint the date of an archeological site better than historic records, but is highly effective for precise dates when calibrated with other dating techniques such as tree-ring dating.
Absolute dating is the process of determining an age on a specified chronology in archaeology and geology.
Some scientists prefer the terms chronometric or calendar dating, as use of the word "absolute" implies an unwarranted certainty of accuracy.
Thus dating that particular tree does not necessarily indicate when the fire burned or the structure was built.
For this reason, many archaeologists prefer to use samples from short-lived plants for radiocarbon dating.
Potassium is common in rocks and minerals, allowing many samples of geochronological or archeological interest to be dated.This technique is based on the principle that all objects absorb radiation from the environment.This process frees electrons within minerals that remain caught within the item.Carbon-14 moves up the food chain as animals eat plants and as predators eat other animals. It takes 5,730 years for half the carbon-14 to change to nitrogen; this is the half-life of carbon-14.After another 5,730 years only one-quarter of the original carbon-14 will remain.Argon, a noble gas, is not commonly incorporated into such samples except when produced in situ through radioactive decay.