Wood is preserved that was used in works of art, cultural artifacts, or for construction of buildings, offering a potential record of hundreds to thousands of years.Subfossil trunks that are buried in peat bogs or river sediments have been preserved for many millennia and can take us even farther into the past.Petrified wood exists that grew millions of years ago and was mineralized, but the rings are still evident.This unique biological archive is the subject of study for dendrochronologists.
The ring widths are measured for tree-ring dating, and wood anatomical features are noted.Cross-dating is used with raw measurements or detrended data sets to establish the sequences' placement in time.The principle of cross-dating is straightforward: trees of the same species growing in the same time in the same geographical region have similar tree-ring patterns.They are the result of cell formation outwards from the pith (the oldest part of the tree).One ring is produced each year (except in some tropical, subtropical, or other difficult areas), within the growing season.