Archaeologists use many different techniques to determine the age of a particular artifact, site, or part of a site.
There are dendrochronological records for Europe and the Aegean, and the International Tree Ring Database has contributions from 21 different countries.
In other words, artifacts found in the upper layers of a site will have been deposited more recently than those found in the lower layers.
Cross-dating of sites, comparing geologic strata at one site with another location and extrapolating the relative ages in that manner, is still an important dating strategy used today, primarily when sites are far too old for absolute dates to have much meaning.
Unfortunately, the wood from the pueblos did not fit into Douglass's record, and over the next 12 years, they searched in vain for a connecting ring pattern, building a second prehistoric sequence of 585 years.
In 1929, they found a charred log near Show Low, Arizona, that connected the two patterns.