Tree ring dating and archaeology
Dendrochronology is useful for determining the precise age of samples, especially those that are too recent for radiocarbon dating, which always produces a range rather than an exact date, to be very accurate.
However, for a precise date of the death of the tree a full sample to the edge is needed, which most trimmed timber will not provide.
Critical to the science, trees from the same region tend to develop the same patterns of ring widths for a given period of chronological study.
Researchers can compare and match these patterns ring-for-ring with patterns from trees which have grown at the same time in the same geographical zone (and therefore under similar climatic conditions).
Direct reading of tree ring chronologies is a complex science, for several reasons.
First, contrary to the single-ring-per-year paradigm, alternating poor and favorable conditions, such as mid-summer droughts, can result in several rings forming in a given year.
Each ring marks a complete cycle of seasons, or one year, in the tree's life.
European chronologies derived from wooden structures initially found it difficult to bridge the gap in the fourteenth century when there was a building hiatus, which coincided with the Black Death, Given a sample of wood, the variation of the tree-ring growths provides not only a match by year, it can also match location because the climate across a continent is not consistent.
New growth in trees occurs in a layer of cells near the bark.
A tree's growth rate changes in a predictable pattern throughout the year in response to seasonal climate changes, resulting in visible growth rings.
Visible rings result from the change in growth speed through the seasons of the year; thus, critical for the title method, one ring generally marks the passage of one year in the life of the tree.
Removal of the bark of the tree in a particular area may cause deformation of the rings as the plant overgrows the scar.
Search for tree ring dating and archaeology:
Dendrochronologists originally carried out cross-dating by visual inspection; more recently, they have harnessed computers to do the task, applying statistical techniques to assess the matching.