In its most conventional form, dendrochronology works like this. They have no bias, and they have no political agenda; they just stand at locations all over the world," says Charlotte Pearson, an assistant professor of dendrochronology at the UA, studies samples under a microscope.A contemporary tree—that is, a tree that was either just cut down or still living—can tell you not just how many years it has lived, but which years in which it lived. Credit: credit: Mari Cleven But what if the wood is older?What we need is a way to account for the ‘relatedness’ of sets of radiocarbon dates. But, using the extra, archaeological information that the dates all come from a particular site that was used for a certain period (and that the site started before it ended!), our model can assess how much of the scatter on the radiocarbon dates comes from statistics and how much is real, historical duration. ‘Relatedness’ is only one of many things which archaeologists know about their material before radiocarbon dating.This lesson can be used as an introduction to radioactivity.Students should have familiarity with the scientific notation and the units milli, micro, and nano.Dating an artifact found on a dig or evaluating the age of a rock requires special kinds of calculations and assessment.
The method has been revolutionary and remains one of the most commonly used dating methods to study the past. Pearson, an assistant professor of dendrochronology at the University of Arizona, studies the past lives of trees to better understand the history of civilizations.
When we calibrate a radiocarbon measurement, we assume that the calendar date of the sample is equally likely to fall at any point on the calibration curve.
For one sample, this is a reasonable assumption; but as soon as we wish to calibrate a second measurement from a site, this assumption is no longer valid (if our first sample is of Iron Age date, then it is much more likely that subsequent samples from the same site will also be Iron Age). The radiocarbon dates on this graph have in reality been simulated from known points on the calendar scale.
Our radiocarbon measurements are from the same site – they are related. Consider these radiocarbon dates – when did Site A (upper) start and end? So, we know that Site A was in use from 2000 to 1800 BC (for 200 years), and that Site B was in use from 1925 to 1885 BC (for 40 years).
Visual inspection, ‘eye-balling’, of graphs of calibrated radiocarbon dates can be really misleading! It starts, it continues in use relatively constantly for some period of time, and it then ends.