or

Define radiocarbon dating. Explain how the age of ancient dead animals and plants can be estimated by using radiocarbon dating.

Radioactive dating can be done by analyzing the fraction of carbon in organic material that is carbon­14.

The ratio of carbon­-14 to carbon­-12 in the atmosphere has been roughly constant over thousands of years. A living plant or tree will be constantly exchanging carbon with the atmosphere and will have the same carbon ratio in its tissues.

When the plant dies, this exchange stops. Carbon-­14  has a half­-life of about 5730 years; it gradually decays away and becomes a smaller and smaller fraction of the total carbon in the plant tissue.  This fraction can be measured, and tissue age deduced.