Fossils are formed in the following way:Usually, when the organisms die, their bodies decompose and be lost. But sometimes the body or at least some parts may be trapped in an environment that does not let it decompose completely and eventually harden and retain the impression of the body parts. All such preserved traces of living organisms form fossils.The age of the fossil can be determined:i. By determining the layer in which the fossil is found. The deeper the layer the older the fossil.\xa0ii. Other method to determine the age of Radio-carbon dating.