Ask an archaeologist how old the site they’re excavating is, and they may not have an answer. Though they may have a hunch, a site can only be accurately dated after it’s been discovered and excavated.

Determining a site’s archaeological age isn’t always easy, but researchers have a variety of relative techniques—methods that provide a rough chronology—and absolute ones—more accurate ways to prove an object’s age—at their disposal.

Relative techniques were developed earlier in the history of archaeology as a profession and are considered less trustworthy than absolute ones. There are several different methods.

In stratigraphy, archaeologists assume that sites undergo stratification over time, leaving older layers beneath newer ones. Like a layer cake or slice of lasagna, a site’s lower