Dendrochronology is the method of determining the age of a piece of wood by counting or comparing tree rings.
Tree rings normally form each year in the trunks of trees because trees grow more quickly in the spring and summer and more slowly in fall and winter. The cells in the wood are smaller and more densely spaced in periods of slow growth, causing a dark 'ring'. Therefore when a living tree is cut down, its age can be determined by counting the rings at the base of the trunk.
However, tree rings can also be used to date much older wooden artifacts. Since trees grow more in years with favorable climates, multi-year weather patterns leave recognizable patterns in tree rings. These patterns are used to identify specific periods of time (in specific places) just as fingerprints can be used to identify a person. Tree ring patterns in old living trees can be matched up to ring patterns in older, dead wood from the same area, to give a chronology of ring patterns that may go back much farther than the life of any one tree (this process is called crossdating). These patterns can then be used to date the wood in artifacts such as houses or tools, or to date the age of different strata in the soil.
Tree-ring dating has been used to calibrate accuracy of the radiocarbon dating process.
- Wile, Dr. Jay L. Exploring Creation With General Science. Anderson: Apologia Educational Ministries, Inc. 2000
- Matthews, Mark, Evidence for multiple ring growth per year in Bristlecone Pines Journal of Creation 20(3), pp. 95-103.