Potassium dating fossils
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.
Additionally, elements may exist in different isotopes, with each isotope of an element differing in the number of neutrons in the nucleus.
For instance, carbon-14 has a half-life of 5,730 years.
After an organism has been dead for 60,000 years, so little carbon-14 is left that accurate dating cannot be established.
Among the best-known techniques are radiocarbon dating, potassium–argon dating and uranium–lead dating.
At a certain temperature, the crystal structure has formed sufficiently to prevent diffusion of isotopes.The procedures used to isolate and analyze the parent and daughter nuclides must be precise and accurate.This normally involves isotope-ratio mass spectrometry. The precision of a dating method depends in part on the half-life of the radioactive isotope involved.Finally, correlation between different isotopic dating methods may be required to confirm the age of a sample.
For example, the age of the Amitsoq gneisses from western Greenland was determined to be Accurate radiometric dating generally requires that the parent has a long enough half-life that it will be present in significant amounts at the time of measurement (except as described below under "Dating with short-lived extinct radionuclides"), the half-life of the parent is accurately known, and enough of the daughter product is produced to be accurately measured and distinguished from the initial amount of the daughter present in the material.This predictability allows the relative abundances of related nuclides to be used as a clock to measure the time from the incorporation of the original nuclides into a material to the present.