By matching plots of abnormally wet and dry years with plots
from samples with known dates, it is possible to build a tree-ring
chronology, or timeline. In order to compile the chronology,
you must know the date of at least one tree ring. A chronology
is constructed from skeleton plots that are flipped upside
The three skeleton plots in the graphic below represent three
different samples of wood. A fire scar in the top sample was
analyzed to deduce that the marked ring grew in the year 1100.
Your task is to match the patterns on the three samples below
to determine the ages of the undated samples.
and drag the samples back and forth to find where the tree
ring patterns match one another exactly. When all three plots are
matched with overlapping patterns, you can count back from
the known date to determine the year that any ring grew.