Geology Reference
In-Depth Information
year by year. How is this possible? Each year, a tree produces a new ring of wood around its trunk. If
the environmental conditions are particularly good, such as when high amounts of rain fall, the ring will
be thicker than in years when conditions are not so good.
With these changes visible in the patterns of the rings, scientists called
dendrochronologists
can com-
pare the rings of multiple trees — a method called
cross-dating
— to build a bridge into the past.
Dendrochronology has been most useful in archaeological and climate studies of the American south-
west. In regions that are arid, trees live a long time and show obvious changes to their growth ring pat-
tern in years of drought or extra rainfall. By correlating these patterns with historic records of weather,
accurate calendar years can be assigned to each ring.
Hundreds of years ago, ancient societies living in the American southwest used wood beams to con-
struct their homes. These beams have been preserved, along with other remnants of their culture and
society. The beams provide a long record of tree rings for cross-dating and examining not only the his-
tory of people in the southwest but also the history of climate change (because the trees record years
of drought and changes in rainfall).
Fission-track dating
