Tree ring dating definition
In the tropical rain forest, relatively few species of trees, such as teak, have visible annual rings.
The difference between wet and dry seasons for most trees is too subtle to make noticeable differences in the cell size and density between wet and dry seasonal growth.
In this example, wood Sample D dates back to the year 1691.
This represents an unbroken succession of 291 annual rings, almost three centuries of time recorded in four small pieces of wood.
Since the rings are so close together, they must be counted under a dissecting microscope.
Three wood cylinders (cores) extracted from the trunk of an old Sierra juniper (Juniperus occidentalis var. Core A has 325 rings, B has 362 rings and C has 412 rings.
By counting the thin bands (annual rings) on the wood cylinder, the approximate age of the tree can be determined.A small core of the wood is removed and the rings are painstakingly counted.This remarkable tree was approximately 1400 years old, and grew on this rugged mountain ridge during the time of Mohammed.Today, scientists have painstakingly established an unbroken succession of rings extending back in time over 80 centuries (8,000 years).
Cross-dating is a valuable tool in dendrochronology and archaeology.
Problems that arise are when climatic variation and suitable trees (sensitive trees react to climatic changes, complacent trees do not) are not be present to produce any significant and recognizable pattern of variation in the rings.