Carbon dating methods archaeology
The Bristlecone pine trees in the Sierra Nevada mountains made this possible and today there are international tree ring databases and agreed-upon calibration curves.
Another problem derives from the “reservoir effect” in which old material, limestone or graphite, has contaminated the samples.
Every living thing on earth contains the element carbon.
When an organism dies, be it a plant or an animal, the carbon acquired during its lifetime begins to decay at a steady, predictable rate, releasing carbon-14, a radioactive isotope with a half-life of 5,730 years.
It was originally believed that the amount of C14 in nature was constant, i.e.
that the decrease of C14 by radioactive decay was replaced by the same amount of new C14 created in the atmosphere.
These artefact types may again be linked with other artefacts types, e.g. By studying how such artefact types appear together, it is possible to build up large artefacts chronologies.When a living organism dies, the amount of C14 decreases without being replaced by new C14. Thus, if a fragment of wood is measured to contain only half of the known proportion of C14 to C12, then the wood was believed to be c. This principle also applies to the dating of artefacts of organic materials.The method has been further refined and developed since Libby invented it.The basis for this dating technique is that there are different carbon isotopes present in nature.C12 and C13 are stable carbon isotopes, while C14 (radiocarbon) is a radioactive isotope. In the atmosphere, C14 combines with oxygen to make CO2, which is then incorporated in plants by photosynthesis, and subsequently in animals eating the plants, eventually reaching the entire biosphere.
One very important advancement was that it was discovered that the amount of C14 in nature is not constant.