See the context of this sign.

Tree-ring Dating

The tree in front of you is Utah juniper (Juniperus
osteosperma). Found today at elevations between 3,000
and 7,000 feet, Utah juniber was used by Tusayan's
prehistoric builders for the main beams in their dwellings.
These trees tell much about Tusayan.

The pattern of tree rings found within wooden beams
helps date the ruin. During dry years tree growth is slow
and rings are narrow. During wet years rings are broader.
Ring patterns on charred wood fragments from kiva roofs
here at Tusayan have been correlated with regional tree
growth data covering many centuries. In this way an
approximated date of A.D. 1185 was determined for the
structures here.

Don't miss the rest of our virtual tour of Tusayan Ruin in 155 images.