Tree ring dating examples
At first it seemed that the dates of many paintings, accurately known from historical records, failed to match their tree-ring dates. Baillie discovered that the tree-ring sequences of western Europe are six years out of phase with the comparable sequences of oak trees that grew in the East European Baltic states.
It seems, therefore, that the Dutch masters imported their wood from Poland or Lithuania. Baillie said, ''all these techniques are based on circumstantial evidence.
So you look for dead trees naturally preserved in bogs.
We find such bogs mainly in Ireland, England and Germany.'' Dr.
By measuring this loss, a scientist can estimate the age of a bone, a piece of wood or any other carbon-based remnant. Stuiver discovered that when the true ages of wooden objects, as calculated from tree rings, are plotted on a graph against the objects' apparent ages, as determined by carbon dating, a wiggly rather than a straight line results.
However, inaccuracies are caused by the fact that the ratio of radioactive carbon to ordinary carbon in the environment varies over the years. The wiggles represent historic fluctuations in the environment that have continuously altered the ratios of carbon 14 to ordinary carbon. Hughes, these wiggles follow the same pattern in both Europe and America, and therefore provide a universal correction scale for carbon dating, at least in the temperate zone of the Northern Hemisphere.
An oak tree typically lives about 250 years and a bristlecone pine may live up to 4,500 years.
Recent studies of tree rings in Europe and the United States have given scientists astonishingly precise new gauges for reconstructing the history of volcanoes, climate and human endeavor in the last 8,500 years. Hughes, director of the dendrochronology laboratory at the University of Arizona, explained in an interview that large volcanic eruptions leave widespread permanent traces in at least two ways.
Tree rings, as distinctively patterned by fluctuations in the environment as bullets are by gun barrels, were recognized half a century ago as potentially useful historical markers. Andrew Ellicott Douglas of the University of Arizona established the science of tree-ring dating, dendrochronology, when he used the rings discernible in ancient wooden artifacts to determine the age of a prehistoric Indian site. Hammer and his colleagues in Denmark analyzed the Greenland ice. First, volcanoes eject large amounts of sulfur dioxide which, when dissolved in water, is precipitated as sulfuric acid in rain or snow.
All living things assimilate carbon from the environment, and a certain proportion is carbon 14.
But when a plant or animal dies, it no longer assimilates carbon, and the carbon 14 it contains gradually decays, losing its radioactivity.
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Similar chronologies have been developed recently in two regions of West Germany.