Dendrochronology dating method
The following article is abstracted from The Biblical Chronologist Volume 5, Number 1. The science of constructing chronologies from tree rings is called dendrochronology. Modern trees are known to produce one growth ring per year. (The idea that ancient trees grew more than one ring per year will be discussed below.) Therefore, by coring a living tree and counting rings from the present backwards, it is possible to determine the year in which each ring grew. The bristlecone pines in the White Mountains of California live to extremely old ages, some in excess of 4,000 years.
The University of Arizona dendrochronology lab sports a (no longer living) specimen which contains over 6,000 rings.
Generally, it is not possible to construct a complete sequence of tree rings back through the historical periods using only living trees.
Chronologies derived from living trees must be extended.
Also, oak trees and bristlecone pine or Douglas fir trees are very different.
The European oak chronology provided an excellent check of the American dendrochronologies. Ring-width patterns are determined by local environmental factors, such as temperature and rainfall.
But for the specimen to be useful in extending the tree-ring chronology, the absolute calendar age of its rings must be determined.