Dendrochronological dating websites
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and which give the result in calendar years before the present, or B. Most of these techniques produce results with a techniques do not.
, in which figures in solar years (often with some necessary margin of error) can be applied to a particular event.
technique for measuring time intervals and dating events and environmental changes by reading and dating the pattern (number and condition) of annual rings formed in the trunks of trees.
The results are compared to an established tree-ring sequence for a particular region with consideration to annual fluctuations in rainfall which result in variations in the size of the rings laid down by trees on the outside of their trunks.
These variations, given favorable conditions, form a consistent pattern; and sections or cores taken from beams in ruins have been matched to provide a long chronology over large areas.
The method is based on the principle that trees add a growth ring for each year of their lives, and that variations in climatic conditions will affect the width of these rings on suitable trees.
In a very dry year growth will be restricted, and the ring narrow, while a wet and humid year will produce luxuriant growth and a thick ring.
By comparing a complete series of rings from a tree of known date (for example, one still alive) with a series from an earlier, dead tree overlapping in age, ring patterns from the central layers of the recent tree and the outer of the old may show a correlation which allows the dating, in calendar years, of the older tree.
The central rings of this older tree may then be compared with the outer rings or a yet older tree, and so on until the dates reach back into prehistory.
Problems that arise are when climatic variation and suitable trees (sensitive trees react to climatic changes, complacent trees do not) are not be present to produce any significant and recognizable pattern of variation in the rings.
Another problem is that there may be gaps in the sequences of available timber, so that the chronology 'floats', or is not tied in to a calendrical date or living trees: it can only be used for .
Also, the tree-ring key can only go back a certain distance into the past, since the availability of sufficient amounts of timber to construct a sequence obviously decreases.
Only in a few areas of the world are there species of trees so long-lived that long chronologies can be built up.