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The Vikings

Tree-Ring Dating Go to Build a Tree-Ring Timeline

Shockwave required

Build a Tree-Ring Timeline
by Rick Groleau

If you're the skeptical type, you might raise an eyebrow when you hear that a particular Viking ship was built in the year 819. How could anyone determine the age of such an aged object so precisely, especially when there are absolutely no records to verify the date?

Well, tree-ring dating, or dendrochronology, can be this precise, and even more so. Dendrochronologists showed that an ancient wooden road uncovered in southwestern England not only was built in 3806 B.C., but that the trees used for the road were chopped down in the winter of that year (the winter of 3807-3806). The science can also reveal the origin of old pieces of wood. In one case, archeologists determined not only the age of a Viking ship found in Denmark, they also learned that it was built in Ireland.

Wood under light Tree rings can reveal more than just a tree's age.

The basis of dendrochronology lies in a tree's unique pattern of growth rings. The rings form a kind of fingerprint—actually, with its irregularly spaced lines, the pattern bears a remarkably close resemblance to a DNA fingerprint. (See Create a DNA Fingerprint.)

Every year a new ring of growth is added to a tree's trunk and branches, just beneath the bark. The thickness of this ring depends on how much the tree grows during the year: favorable growing conditions result in a fat ring, unfavorable conditions, in a narrow ring. And because trees in a given area generally experience the same growing conditions, those trees have similar tree-ring patterns.

By starting with a living tree and working back, using wooden objects of different ages, dendrochronologists have created continuous chains of tree rings that stretch back hundreds, sometimes even thousands, of years. They then use these tree-ring chronologies to date wooden objects, to determine a general area in which the wood grew, to find out about past climates, and more.

This Hot Science lets you assemble your own tree-ring chronology. You'll start with a tree-ring sample from a living tree and, using other samples, piece together a pattern of rings that stretches back through time.

    Build a Tree-Ring Timeline
        requires the Shockwave plug-in
    Anatomy of a Tree Ring
    Growth and Sensitivity
    Skeleton Plots

Explore a Viking Village | Who Were the Vikings?
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