Telling Time
Imagine trying to tell a story without being able to place events in order from beginning to end. In order to trace changes through time, archaeologists must first determine the ages of different sites. The archaeologists involved in this research focused on pottery to date sites, studying thousands of whole pots and potsherds (fragments of pottery vessels) in existing museum collections. The pottery had been recovered from dozens of sites throughout the southern Southwest. The researchers’ findings allowed them to date sites with much greater precision, providing a clearer perspective on how Hohokam culture changed after A.D. 1300.
In the Southwest, most dates assigned to pottery rely on tree-ring dating or dendrochronology. Trees usually add yearly growth rings. For conifers (pines, firs, and spruces), a wide ring indicates a wet year, and a narrow one marks a dry year. Because archaeologists have traced the history of wet and dry years over a period of centuries, they can match the pattern of narrow and wide rings in wooden construction beams found in archaeological sites.
Archaeologists have observed that certain kinds of pottery were associated with certain date ranges. Specimens of a kind of pottery found in sites without tree-ring dates are assumed to be the same age as specimens of the same kind of pottery found at sites with tree-ring dates. Often, pottery in the desert (where pines, firs, and spruces are usually absent) has been dated as a result of being found with tree-ring dated pottery made in the mountains or on the Colorado Plateau.
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Key Points:
Archaeologists can date sites using pottery. Archaeologists can determine the age of a pottery type using tree-ring dating. Changes through time in painted decoration and bowl shapes have helped archaeologists define a number of new pottery types. These new pottery types can be used to more precisely determine how long different sites were occupied, helping archaeologists track changes in population. |
This online exhibit was created in partnership with Pueblo Grande Museum, and is made possible by grants from the National Science Foundation.
