Some species of trees can live for thousands
of years. Because the widths of a tree's rings
reflect yearly precipitation patterns, the rings
can be analyzed to reconstruct a record of past
Tree rings also record the occurrence of forest
fires. New layers of wood added around the exterior
of tree trunks are vulnerable to damage by fire.
If a fire damages a tree's bark and exterior,
but does not kill the tree, a new layer of wood
can grow over the scarred layer the next year,
preserving the scar as a record of the fire.