Station: [138] Dating Methods

Dendrochronology comes from Greek: Dendron means tree, chronos, time and logos, the teaching. The age of a tree can be calculated from the growth rings in a horizontal cross-section of it. You can see some examples of horizontal cross sections in the tree on the left-hand side of the showcase. 

If you look closely you’ll see that the rings differ in width. This is caused by climate. The pattern created is similar to a fingerprint. The ring succession can be measured and portrayed in the form of curves. Regional chronological curves can be calculated and compiled from the overlapping ring patterns in wood that has been used in buildings, such as timber-framed houses for example. The curves of non-dated woods can also be compared with these and their age calculated from the results. Woods such as oak, fir and pine are well suited to dendrochronological examination.

Can you see the tree on the right hand side of the showcase? We have installed a touch screen on it so that you can have a go at the curve game! 

Radiocarbon dating is another way of calculating the age of something. This is based on the rate of decay of unstable carbon isotopes, C14 atoms that are created in the earth’s atmosphere by cosmic radiation. Alongside stable C12 atoms living organisms also absorb C14 atoms. When an organism dies, the C14 atoms begin to decay. After 5730 years only half of them remain, while the amount of C12 atoms remains the same. The ratio of C14 to C12 atoms allows researchers to calculate how many years have passed since the organism died.

But radio carbon dating isn’t 100% accurate because the C14 content in the atmosphere is too variable, so radiocarbon dating is compared to tree growth rings that have already been dated exactly using dendrochronology.