Carbon 14 radiometric dating

Growth rings are the result of new growth in the vascular cambium, a layer of cells near the bark that is classified as a lateral meristem; this growth in diameter is known as secondary growth.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.

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Cross-dating was originally done by visual inspection; more recently, computers have been harnessed to do the task, applying statistical techniques to assess the matching.For instance, the bristlecone pine is exceptionally long-lived and slow growing, and has been used extensively for chronologies; still-living and dead specimens of this species provide tree-ring patterns going back thousands of years, in some regions more than 10,000 years. P., the radiocarbon dates are calibrated against dendrochronological dates.Currently, the maximum span for fully anchored chronology is a little over 11,000 years B. In 2004 a new radiocarbon calibration curve, INTCAL04, was internationally ratified to provide calibrated dates back to 26,000 B. Dendrochronology practice faces many obstacles, including the existence of species of ants that inhabit trees and extend their galleries into the wood, thus destroying ring structure.To eliminate individual variations in tree-ring growth, dendrochronologists take the smoothed average of the tree-ring widths of multiple tree samples to build up a ring history, a process termed replication.A tree-ring history whose beginning and end dates are not known is called a floating chronology.