Why did geologists develop the geologic time scale?

Answer 1

The geological time scale is the geologic history of the planet from formation to the present. It starts with large divisions of time called eons and is subdivided into successively smaller units of time based on dominant lifeforms, extinction events, even climate. The development of the geologic time scale was initially based on the observation and reasoning that deeper layers of rock are generally older than less deep layers in what is called the "Law of Superposition".

Paleontologists look for index fossils in fossil bearing sedimentary rock. Index fossils are organisms that were widespread, rapidly evolving, and only existed for a short period of time as evidenced by their appearance in the fossil record of specific rock strata. The appearance of a fossil alongside an index fossil gives a rough approximation of the age of the fossil in relative terms as it would appear on the geologic time scale. The appearance of the same fossil alongside index fossils of different geologic ages means that the fossil organism spanned multiple geologic time periods. Associations of specific strata alongside radiographically datable igneous and metamorphic rock determines the absolute age of a fossil.

A period of around 4,600,000,000 years, the largest groupings of geologic time are eons, followed in descending order by era, period, epoch, and age.

The geologic time scale is very important, especially in fields involving the exploration and retrieval of fossil fuels, which are geologically date range specific.

Answer 2

to find out how long the fossil has been hear

Answer 3

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