These variations, given favorable conditions, form a consistent pattern; and sections or cores taken from beams in ruins have been matched to provide a long chronology over large areas.The method is based on the principle that trees add a growth ring for each year of their lives, and that variations in climatic conditions will affect the width of these rings on suitable trees.date of organic material - but an approximate age, usually within a range of a few years either way.The other method is “Relative Dating” which gives an order of events without giving an exact age (1): typically artefact typology or the study of the sequence of the evolution of fossils.The behavioral aspect of tree-ring dating, meanwhile, allows archaeologists to understand ancient wood-use practices, trade, and other activities.Tree-ring dating may only be performed on tree species that produce one growth ring per year, and do so in response to annual variations in precipitation (and in some cases temperature).
By comparing a complete series of rings from a tree of known date (for example, one still alive) with a series from an earlier, dead tree overlapping in age, ring patterns from the central layers of the recent tree and the outer of the old may show a correlation which allows the dating, in calendar years, of the older tree.
It also has some applications in geology; its importance in dating organic materials cannot be underestimated enough.
In 1979, Desmond Clark said of the method “we would still be foundering in a sea of imprecisions sometime bred of inspired guesswork but more often of imaginative speculation” (3).
This chronometric technique is the most precise dating tool available to archaeologists who work in areas where trees are particularly responsive to annual variations in precipitation, such as the American Southwest. These cross-dated sequences, called chronologies, vary from one part of the world to the next. Douglass pioneered the science of tree rings in this 1929 article titled "The Secret of the Southwest Solved by Talkative Tree Rings." Includes numerous fascinating historic photographs.
Douglass in the 1920s, dendrochronology—or tree-ring dating—involves matching the pattern of tree rings in archaeological wood samples to the pattern of tree rings in a sequence of overlapping samples extending back thousands of years.