Radiocarbon dating dendrochronology
If we have a tree that is 500 years old we can measure the radiocarbon in the 500 rings and see what radiocarbon concentration corresponds to each calendar year.Using very old trees (such as the Bristlecone Pines in the western U. A.), it is possible to make measurements back to a few thousand years ago.After the death of the organism, processes of decay will return its carbon to the atmosphere, unless it is sequestered — for example in the form of coal.This means that when an organism is alive, its ratio of C dating, or C-C dating.After about 60,000 years the quantity will be too small for our instruments to measure accurately, and the best we'll be able to say is that the sample is about 60,000 years old or more.For this reason radiocarbon dating is of more interest to archaeologists than to geologists.One of the nice things about this method is that we don't have to worry about carbon being lost from the sample.
Method A scientific date is either absolute (specific to one point in time) or relative (younger or older than something else).
Radiocarbon measurements are always reported in terms of years `before present' (BP).
This figure is directly based on the proportion of radiocarbon found in the sample.
About 21 pounds of Nitrogen is converted each year making about 1/trillion atmospheric carbon atoms radioactive C.
Then an age can be obtained for the organic material.
Greatly simplified, the process samples living and dead trees in a given area.