Bone dating techniques
An additional problem with carbon-14 dates from archeological sites is known as the "old wood" problem.It is possible, particularly in dry, desert climates, for organic materials such as from dead trees to remain in their natural state for hundreds of years before people use them as firewood or building materials, after which they become part of the archaeological record.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.Techniques include tree rings in timbers, radiocarbon dating of wood or bones, and trapped-charge dating methods such as thermoluminescence dating of glazed ceramics.Coins found in excavations may have their production date written on them, or there may be written records describing the coin and when it was used, allowing the site to be associated with a particular calendar year.In historical geology, the primary methods of absolute dating involve using the radioactive decay of elements trapped in rocks or minerals, including isotope systems from very young (radiocarbon dating with Radiometric dating is based on the known and constant rate of decay of radioactive isotopes into their radiogenic daughter isotopes.
Potassium is common in rocks and minerals, allowing many samples of geochronological or archeological interest to be dated.
It cannot be used to accurately date a site on its own.
However, it can be used to confirm the antiquity of an item.
The development of accelerator mass spectrometry (AMS) dating, which allows a date to be obtained from a very small sample, has been very useful in this regard.
Other radiometric dating techniques are available for earlier periods.
The relatively short half-life of carbon-14, 5,730 years, makes dating reliable only up to about 50,000 years.