Two effects also interfere with the dating of very recent samples.The testing of thermonuclear weapons produced an increase in atmospheric C they contain is infinitesimal.After the death of the organism, processes of decay will return its carbon to the atmosphere, unless it is sequestered — for example in the form of coal.This means that when an organism is alive, its ratio of C dating, or C-C dating.
Around the world, only about 100 facilities house this equipment.
After about 60,000 years the quantity will be too small for our instruments to measure accurately, and the best we'll be able to say is that the sample is about 60,000 years old or more.
For this reason radiocarbon dating is of more interest to archaeologists than to geologists.
The carbon-14 isotope would vanish from Earth's atmosphere in less than a million years were it not for the constant influx of cosmic rays interacting with molecules of nitrogen (NFigure 1: Diagram of the formation of carbon-14 (forward), the decay of carbon-14 (reverse).
Carbon-14 is constantly be generated in the atmosphere and cycled through the carbon and nitrogen cycles.