The relatively short half-life of carbon-14, 5,730 years, makes dating reliable only up to about 50,000 years.

potassium argon dating simplified-61

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.

The method works best if neither the parent nuclide nor the daughter product enters or leaves the material after its formation.

Anything which changes the relative amounts of the two isotopes (original and daughter) must be noted, and avoided if possible.

All ordinary matter is made up of combinations of chemical elements, each with its own atomic number, indicating the number of protons in the atomic nucleus.

Elements exist in different isotopes, with each isotope of an element differing in the number of neutrons in the nucleus.Different dating methods may be needed to confirm the age of a sample.For example, a study of the Amitsoq gneisses from western Greenland used five different radiometric dating methods to examine twelve samples and got agreement to within 30 million years on an age of 3,640my.It may be used to date a wide range of natural and man-made materials.Fossils may be dated by taking samples of rocks from above and below the fossil's original position.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.