GEOLOGY

Detailed explanation-1: -Index fossils are used to determine the age of a rock stratum of sedimentary rock. They are useful in this way because the index fossil species only lived for a short period of geological time, which still may be several million years.

Detailed explanation-2: -If the same index fossil is found in different areas, the strata in each area were likely deposited at the same time. Thus, the principle of faunal succession makes it possible to determine the relative age of unknown fossils and correlate fossil sites across large discontinuous areas.

Detailed explanation-3: -The law of superposition is one of the principles of geology scientists use to determine the relative ages of rock strata, or layers. This principle states that layers of rock are superimposed, or laid down one on top of another. The oldest rock strata will be on the bottom and the youngest at the top.

Detailed explanation-4: -The age of rocks is determined by radiometric dating, which looks at the proportion of two different isotopes in a sample. Radioactive isotopes break down in a predictable amount of time, enabling geologists to determine the age of a sample using equipment like this thermal ionization mass spectrometer.

Detailed explanation-5: -Index fossils are used to define geological periods. These fossils can be defined as “commonly found, widely distributed fossils that are limited in time span.” If one finds an index fossil in a given layer, then one has bounds on the age of the layer. Using index fossils, the geological periods are defined.