Douglass believed that solar flares affected climate, and hence the amount of growth a tree might gain in a given year.His research culminated in proving that tree ring width varies with annual rainfall.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.Using local pine trees, Douglass built a 450 year record of the tree ring variability.Clark Wissler, an anthropologist researching Native American groups in the Southwest, recognized the potential for such dating, and brought Douglass subfossil wood from puebloan ruins.
First used, and likely invented by archaeologist Sir William Flinders-Petrie in 1899, seriation (or sequence dating) is based on the idea that artifacts change over time.
The scholar most associated with the rules of stratigraphy (or law of superposition) is probably the geologist Charles Lyell.
The basis for stratigraphy seems quite intuitive today, but its applications were no less than earth-shattering to archaeological theory.
Like tail fins on a Cadillac, artifact styles and characteristics change over time, coming into fashion, then fading in popularity. The standard graphical result of seriation is a series of "battleship curves," which are horizontal bars representing percentages plotted on a vertical axis.
Plotting several curves can allow the archaeologist to develop a relative chronology for an entire site or group of sites.