Relative age refers to the age of a rock, fossil, or mineral compared to other surrounding material. It is an approximate age determination made by comparing whether the material is younger or older than other surrounding material. Relative age can be estimated according to stratigraphic and structural relationships, such as superposition, and by fossil content, since the relative ages and successions of fossils have been established by paleontologists. The Law of Superposition is a principle used to determine relative age, which states that newer rock layers form on top of already existing layers, so the older rock layers end up at the bottom and the newer ones toward the top.
Relative age is different from absolute age, which is the numeric age of a layer of rocks or fossils and can be determined by using radiometric dating. The measurement of the decay of radioactive isotopes, especially uranium, rubidium, argon, and carbon, has allowed geologists to more precisely determine the absolute age in years of rock formations.
In summary, relative age is an approximate age determination made by comparing whether the material is younger or older than other surrounding material, while absolute age is the numeric age of a layer of rocks or fossils.
