3. Determination of age of fossils

So far, we have discussed what fossils, the different types of fossilization are. But how can we know the age of a fossil?

Relative dating and absolute dating are the two main methods for determining the age of a fossil. By comparing a fossil to similar rocks and fossils of known ages, relative dating can estimate its age.

It is a method that provides the age estimates of living organisms that consume carbon. It was discovered by W.F. Libby \((1956)\). It is based on the fact that cosmic rays interact with atmospheric nitrogen to produce radiocarbon$C^{14}$ in the Earth's atmosphere on a continuous basis. The resulting $C^{14}$ reacts with atmospheric oxygen to generate radioactive carbon dioxide, which is absorbed by plants through photosynthesis and consumed by acquired by animals while consuming them.

 

When these plants and animals die, they stop exchanging carbon with their environment, and after that, the amount of $C^{14}$ present in them begin to decrease as the $C^{14}$ undergoes radioactive decay. The time passed since death of a plant or animal can be calculated by measuring the amount of $C^{14}$ present in their body. The amount of $C^{14}$ in a sample from a dead plant or animal, such as a piece of wood or a fragment of bone, can be used to compute when the animal or plant died.