Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed. As well as dating them, this can give data for dendroclimatology, the study of climate and atmospheric conditions during different periods in history from wood.

How are tree rings used for direct dating?

Direct Dating of Wood Cross-dating determines the age of undated wood by directly matching ring patterns with trees of known age. Greatly simplified, the process samples living and dead trees in a given area. The tree-ring patterns are matched, and laid down in series, building a continuous timeline of known dates.

How do you date a tree-ring?

The most common, most accurate way to find the age of a tree is to count the number of rings visible when their trunk is cut horizontally. Each year, most trees add an extra layer of growth to their trunks. Over time, their trunks get thicker and thicker.

How do we determine the age of a tree?

The girth of a tree can be used to estimate its age, as roughly a tree will increase its girth by 2.5cm in a year. So, simply measure around the trunk of the tree (the girth) at about 1m from the ground. Make sure you measure to the nearest centimetre. Then divide the girth by 2.5 to give an age in years.