Radiocarbon dating samples
There are two main methods used for calculating age ranges from the calibration curve: The first method to be employed was called the `intercept method' because it can be done by drawing intercepts on a graph.This method will tell you the years in which the radiocarbon concentration of tree rings is within two standard deviations of your measurement (e.g.This plot shows how the radiocarbon measurement 3000 -30BP would be calibrated.The left-hand axis shows radiocarbon concentration expressed in years `before present' and the bottom axis shows calendar years (derived from the tree ring data).It is calculated on the assumption that the atmospheric radiocarbon concentration has always been the same as it was in 1950 and that the half-life of radiocarbon is 5568 years.For this purpose `present' refers to 1950 so you do not have to know the year in which the measurement was made.The wood in these rings once laid down remains unchanged during the life of the tree.
The second is directly derived from this on the assumption that the half-life of radiocarbon is 5568 years and the amount of radiocarbon in the atmosphere has been constant.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.The results of calibration are often given as an age range.In this case, we might say that we could be 95% sure that the sample comes from between 1375 cal BC and 1129 cal BC.
Search for radiocarbon dating samples:
between 2940BP and 3060BP for the measurement 3000 -30BP).