Today let’s explore another scientific method in archaeology – this time, a bit more of a natural one! Dendrochronology is a fascinating study, and often very important to Archaeology. The word Dendrochronology is made up of three Greek words, which refer to the study of data using tree rings.
And how does it work? Well, if you ever counted the rings on a tree trunk slice, you may know that each ring was grown in one year. So if you count the rings, you can work out how old the tree is.
In many old houses, at least parts of the building are made of wood. Once the wood is dated, you will know how long the house has stood for after the wood was cut. The wood itself may be dated using other means, such as Carbon 14 dating, and the date that the wood was cut will be found. Using this age, the time AFTER the age of the wood is added up, giving the oldest possible age of the house.
Dendrochronology also can help us learn about the climate in the past. This is because the growth of the tree rings is affected by the climate – in a good year of plenty of water, the rings will grow thick, but in a drought, they will be very thin, even nonexistence. See in the photo above, the ring size varies.
But whilst archaeologists can date the wood to when it was felled, it may be harder to date the building or structure that the wood was used for, as the wood may be older that the actual structure. For instance, the wood may have been reused from an older structure, it may have been felled, then left for many years before it was used, or it may have been used to replace a damaged piece of wood.
On top of this, when wood is used in buildings, it will most often be cut selectively into the shape of pieces needed. This means that some of the wood (and tree rings) are lost, meaning that it cannot be effectively dated. However, there are some structures that are able to be dated perfectly, if the correct criteria are in place. For instance, there are a number of prehistoric forms of buildings (like hillforts and such) that use whole posts, cut from tree trunks. These are often used stacked together, forced upright in the earth to form a barrier to prevent unwanted entrance to the fort. This is fantastic for archaeologists!
Though the posts may not have survived, there would be traces of the holes where they stood. These can be measured, thus giving an estimate size for the post that once would have stood there.
There’s plenty more to learn about Dendrochronology, so you may wish to look further into this fascinating study! Until next time,