The activity below allows you to build a tree-ring chronology.
Each horizontal bar represents the tree-ring pattern for one
tree. By looking for matches in the patterns, you should be
able to build an overlapping sequence that stretches back in
time. You can move the chronology to the right and left using
the arrows. Afterwards, go on to the next feature (see
below).
The technique used here to create a chronology of tree-ring
patterns is similar to the one that dendrochronologists use.
Called crossdating, the process has established tree-ring
chronologies for many areas around the world.
Some of these chronologies extend back thousands of years. In
the American Southwest, using both living and dead samples
from the long-lived bristlecone pine (the oldest one has been
growing for a remarkable 4,600 years), scientists have
constructed a continuous history of tree rings that stretches
back almost 9,000 years, to about the year 6700 B.C.
Note: This activity is meant simply to illustrate the
principles involved in creating a tree-ring chronology. In
creating actual chronologies, dendrochronologists make use
of
skeleton plots, which are graphical representations of tree-ring
patterns.