Dendrochronology

is the science that deals with the dating and studying of annual growth layers in wood.

The Value of Dendrochronology

It is the most accurate dating technique that we use today. It provides annual and even seasonal resolution throughout the entire record. Other records such as varved lake sediments, some ice cores, and coral records can provide annual resolution but it is not as consistently reliable as dendrochronology. Another factor that makes dendrochronology a useful tool is that trees are ubiquitous on the landscape. Most terrestrial-temperate regions of the globe have trees present that can be useful to the techniques of dendrochronology.

Time Frame of Dendrochronology

The time frame of dendrochronology covers anywhere from the present back 10,000 years. But most chronologies are only a few hundred years long. There are some 1,000 year long chronologies scattered around the globe, but they are rare.

Short History and Scope of Dendrochronology

Dendrochronology was developed by A.E. Douglass, founder of the first laboratory entirely devoted to tree-ring research. Douglass' initial interest was the impact of solar cycles on the Earth’s climate. While working in Flagstaff, Arizona in A.D. 1904, he noticed a distinct annual ring pattern in the stems of many ponderosa pine trees, a repeated signature of narrow and wide rings. This now famous pattern, which Douglass subsequently found in trees throughout the region, became known as the Flagstaff signature. Ring-width patterns enable dendrochronologists to precisely and accurately date every individual tree ring in a chronology.
When all trees on a site are limited by a common factor, such as inter-annual variability in climate, the size of their annual growth rings is affected in a similar manner, and a common ring-width pattern emerges across the site or region. Crossdating, i.e., matching the ring patterns in tree-ring samples across a site, can provide an accurate chronological record of the natural history of the stand.

Among other applications, dendrochronology has been used to date:
           - Archeological ruins
           - Climate change
           - Fire history
           - Insect outbreaks
           - Volcanic eruptions
           - Glacier movement