Radiocarbon dating

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Radiocarbon dating is one of the most widely used scientific dating methods in archaeology and environmental science.It can be applied to most organic materials and spans dates from a few hundred years ago right back to about 50,000 years ago - about when modern humans were first entering Europe.Common materials for radiocarbon dating are: The radiocarbon formed in the upper atmosphere is mostly in the form of carbon dioxide. Because the carbon present in a plant comes from the atmosphere in this way, the radio of radiocarbon to stable carbon in the plant is virtually the same as that in the atmosphere.Plant eating animals (herbivores and omnivores) get their carbon by eating plants.Once the organism dies, however, it ceases to absorb carbon-14, so that the amount of the radiocarbon in its tissues steadily decreases.Carbon-14 has a half-life of 5,730 ± 40 years— during the succeeding 5,730 years.The pathway from the plant to the molecule may have been indirect or lengthy, involving multiple physical, chemical, and biological processes.Levels of C can represent either mixtures of modern and dead carbon or carbon that was fixed from the atmosphere less than 50,000 years ago.

All carbon atoms have a nucleus containing six protons.

They have masses of 13 and 14 respectively and are referred to as "carbon-13" and "carbon-14." If two atoms have equal numbers of protons but differing numbers of neutrons, one is said to be an "isotope" of the other.

Carbon-13 and carbon-14 are thus isotopes of carbon-12.

Obviously there will usually be a loss of stable carbon too but the proportion of radiocarbon to stable carbon will reduce according to the exponential decay law: R = A exp(-T/8033) where R is C ratio of the living organism and T is the amount of time that has passed since the death of the organism.

By measuring the ratio, R, in a sample we can then calculate the age of the sample: T = -8033 ln(R/A) Both of these complications are dealt with by calibration of the radiocarbon dates against material of known age.

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