Cross dating in dendrochronology douglass
Critical to the science, trees from the same region tend to develop the same patterns of ring widths for a given period of chronological study.
It can be anchored by cross-matching a section against another chronology (tree-ring history) whose dates are known.
When one can match these tree-ring patterns across successive trees in the same locale, in overlapping fashion, chronologies can be built up—both for entire geographical regions and for sub-regions.
Moreover, wood from ancient structures with known chronologies can be matched to the tree-ring data (a technique called cross-dating), and the age of the wood can thereby be determined precisely.
During the first half of the twentieth century, the astronomer A. Douglass founded the Laboratory of Tree-Ring Research at the University of Arizona.
Douglass sought to better understand cycles of sunspot activity and reasoned that changes in solar activity would affect climate patterns on earth, which would subsequently be recorded by tree-ring growth patterns (i.e., sunspots → climate → tree rings).