Site map . Science books Looking at history through a gnarled pine By Randy Ringen, FutureWatch . 09.27.99 S cientists determine the age of trees by counting their thousands of rings, one for each year of their lives. About the column . The bristlecone pine is an often gnarled tree that grows in the Western United States.
Some varieties live several thousand years.
Also, scientists match core samples of living bristlecone pines with those nearby that have been long dead. By finding where similar patterns of different ring sizes overlap and match, they can create a continuous tree ring record that extends back more than ten thousand years. Each tree ring is also a record of the dust in the atmosphere for each year of the tree's life. Airborne debris, whether from volcanic eruptions, pollution, or atomic fallout, are absorbed by the tree and find their way into the particular ring growing at the time. After a tree dies, the process of absorption stops.