Radiocarbon dating calibration curve
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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.
Direct reading of tree ring chronologies is a learned science, for several reasons.
A new layer of wood is added in each growing season, thickening the stem, existing branches and roots, to form a growth ring.
Growth rings, also referred to as tree rings or annual rings, can be seen in a horizontal cross section cut through the trunk of a tree.
A tree's growth rate changes in a predictable pattern throughout the year in response to seasonal climate changes, resulting in visible growth rings.
Each ring marks a complete cycle of seasons, or one year, in the tree's life.
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.The inner portion of a growth ring is formed early in the growing season, when growth is comparatively rapid (hence the wood is less dense) and is known as "early wood" (or "spring wood", or "late-spring wood" Many trees in temperate zones make one growth ring each year, with the newest adjacent to the bark.Hence, for the entire period of a tree's life, a year-by-year record or ring pattern is formed that reflects the age of the tree and the climatic conditions in which the tree grew.It is also used in radiocarbon dating to calibrate radiocarbon ages.New growth in trees occurs in a layer of cells near the bark.These patterns can be compared and matched ring for ring with trees growing at the same time in the same geographical zone (and therefore under similar climatic conditions).