Radiocarbon dating, right? How does that work, and how can we ensure its accuracy?
In: Planetary Science
Radiocarbon dating is calibrated using tree rings, oddly enough. Dendrochronology uses tree rings to count backwards from when the tree was cut, to its first ring. Trees outside tropical regions grow in the summer and stop in the winter, leaving an annual record. The growth rings vary in thickness depending on how good the growing season was (temperature, rainfall, etc).
Fortunately for dendrochronologists, trees can live a long time. So if you find a recently felled 100 year old tree, you have a pattern of tree rings unique to that time period and region. Now, suppose you have a 50 year old structure that has a large beam that itself was made from a 100 old tree. You can match up the overlapping years with the first tree and know not only what year the tree was felled, but now you have a record going back 150 years. Repeat that a number of times and you can date any piece of the same type wood in the region.
Now, radiocarbon date all those pieces of wood. Since you know very accurately the real date, you can build a chart of radiocarbon content to actual years and correct the radiocarbon date The C14 content of the atmosphere varies based on solar activity, so this is a really important technique. Also, C14 in the atmosphere is homogeneous, so if you’re dendrochronology is based on European oak and pine (which is the most complete dataset), the correction still works for finds in, say, Australia.
Latest Answers