Archaeological Dating

Significant progress has been made in this field of study since the discovery of radioactivity and its properties. One application is carbon-14 dating. Recalling that all biologic organisms contain a given concentration of carbon-14, we can use this information to help solve questions about when the organism died. It works like this..when an organism dies it has a specific ratio by mass of carbon-14 to carbon-12 incorporated in the cells of it's body. (The same ratio as in the atmosphere.) At the moment of death, no new carbon-14 containing molecules are metabolized, therefore the ratio is at a maximum. After death, the carbon-14 to carbon-12 ratio begins to decrease because carbon-14 is decaying away at a constant and predictable rate. Remembering that the half-life of carbon-14 is 5700 years, then after 5700 years half as much carbon-14 remains within the organism.

CHEM WINDOW - Half-life

Example : If an organism such as a tree contained 1 gram of carbon-14 while it was living, then after 5700 years it would contain half that amount, or 0.5 grams of carbon-14.

This method of dating using carbon-14 is only good for organisms or artifacts that are biological by nature and on the order of tens of thousands or years old.

What isotope would be increasing due to the decay of carbon-14?

Could this method of dating be used to estimate the age of petroleum deposits?

What human activities could alter the carbon-14/carbon-12 ratio?