Submitted by Anonymous on Sat, 08/09/2008 - 10:15
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Kuril Islands Biocomplexity 08

How does charcoal help you guys tell the time period of the settlement?

Grady Thomas 

Wed, 08/13/2008 - 10:32

KBP Team

Without delving too deeply into the chemistry behind it, we use charcoal to obtain a radiocarbon date, which is sometimes called a carbon-14 (C14) date. Basically the way it works is this: every living thing is made up of carbon, and a very small amount of the carbon in those living things is C14. After that living thing dies, theamount of C14 slowly reduces at a predictable rate through a process called radioactive decay. Don't worry-the amount of radiation coming out of C14 decay is really really tiny and won't hurt you. Anyway, if we
1. know how much C14 is in the living thing, like a tree or a stick or a bird bone,
2. and then we measure how much C14 is in the old piece of charcoal or bone that we find in an archaeological site,
3. and we know what the decay rate is,
then we can calculate how long ago that thing died.
But there is a very important thing about C14 dating to remember, and that is that what we are dating (called the "sample date") is the death of that organism. But in archaeology, we usually want to know the answer to "when were people here?" That's called the "target date." Ideally, the sample date and the target date happened at about the same time. So we can't just date any old piece of charcoal-we first make sure that it came from an archaeological site.
-- Dr. E.