Absolute dating definition
Tree ring dating offers over 1,000 years of clues in dates of artifacts from the American Southwest.
Radiocarbon dating provides additional clues necessary for absolute dating.
Absolute dating provides a numerical age or range in contrast with relative dating which places events in order without any measure of the age between events.
In archaeology, absolute dating is usually based on the physical, chemical, and life properties of the materials of artifacts, buildings, or other items that have been modified by humans and by historical associations with materials with known dates (coins and written history).
The half-life of potassium-40 is 1.3 billion years, far longer than that of carbon-14, allowing much older samples to be dated.
Coins found in excavations may have their production date written on them, or there may be written records describing the coin and when it was used, allowing the site to be associated with a particular calendar year.
An additional problem with carbon-14 dates from archeological sites is known as the "old wood" problem.
It is possible, particularly in dry, desert climates, for organic materials such as from dead trees to remain in their natural state for hundreds of years before people use them as firewood or building materials, after which they become part of the archaeological record.
With the passing of time, new strata form over them.
Thus, the date of an artifact is relative to its location in the levels.