Relative dating stratigraphy
In 1929, they found a charred log near Show Low, Arizona, that connected the two patterns.
It was now possible to assign a calendar date to archaeological sites in the American southwest for over 1000 years.
His research culminated in proving that tree ring width varies with annual rainfall.
Not only that, it varies regionally, such that all trees within a specific species and region will show the same relative growth during wet years and dry years.
Archaeologists use many different techniques to determine the age of a particular artifact, site, or part of a site.
Two broad categories of dating or chronometric techniques that archaeologists use are called relative and absolute dating.
In 1901, Douglass began investigating tree ring growth as an indicator of solar cycles.
Douglass believed that solar flares affected climate, and hence the amount of growth a tree might gain in a given year.
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.Since the turn of the century, several methods to measure elapsed time have been discovered.The first and simplest method of absolute dating is using objects with dates inscribed on them, such as coins, or objects associated with historical events or documents.Plotting several curves can allow the archaeologist to develop a relative chronology for an entire site or group of sites.For detailed information about how seriation works, see Seriation: A Step by Step Description.