One of the most widely used is potassium-argon dating (K-Ar dating).
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.
This is a radiometric technique since it is based on radioactive decay.
Cosmic radiation entering the earth’s atmosphere produces carbon-14, and plants take in carbon-14 as they fix carbon dioxide.
For example, techniques based on isotopes with half lives in the thousands of years, such as Carbon-14, cannot be used to date materials that have ages on the order of billions of years, as the detectable amounts of the radioactive atoms and their decayed daughter isotopes will be too small to measure within the uncertainty of the instruments.
One of the most widely used and well-known absolute dating techniques is carbon-14 (or radiocarbon) dating, which is used to date organic remains.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.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.An additional problem with carbon-14 dates from archeological sites is known as the "old wood" problem.