People from all over the world study the Mesa Verde in the South West region because these archaeological sites hold rich data. The arid climate, large number of sites, and well-preserved wood in those sites have made it possible to develop a more complete chronology of this region than anywhere else in the world.  Trees produce growth rings of different sizes every year that reveal changes in precipitation.  Scientists use tree rings to pinpoint construction dates of buildings.

Notice the tiny rings on the tree stump. Each ring represents approximately one year of growth. 

How many years did this tree live before being cut down? 

Scientists make a timeline of the Mesa Verde region by matching and overlapping cores from living piñon and juniper trees with rings from dead trees of the same species. Once a master timeline or chronology is created, scientists can use it to date the wood from archaeological sites giving them an approximate date for the site or artifact.

This structure style is common to the Southwestern United States. This photo was taken in Southern Colorado or Northern New Mexico. Note the wood beams common in ancestral Puebloan structures and common to adobe structures today.

Photograph of adobe structure with wood log beams.  This structure style is common to the Southwestern United States.  This photo was taken in Southern Colorado or Northern New Mexico.

Negative, Adobe structure photo

History Colorado

Scientists match cores from beams in ancient buildings with a master timeline. Sometimes Ancestral Pueblo people reused wood from old buildings, so researchers collect cores from several beams in a home or kiva to make sure they’re dating it accurately.

How do you think researchers know that the wood was reused? 

3 Tree Ring Cores from southwest Colorado.  Important for dendrochronology

Standards for Tree Rings Can Tell Time

College, Career, and Civic Life (C3) Framework