Explain how fossils were used to develop early geologic time scales.

Fossils refer to the remains of the past life like shells, bones, or other tough parts, and it may also comprise the proof of past life-like leaf impressions or footprints. A geologic time scale refers to the timeline, which demonstrates the past time of the Earth.  

The planet in which we live is very old, and the study of the past of the Earth needs one to think about the times, which were millions or billions of years old. The geologic time scale is used by scientists to explain how the incidents took place on Earth.  

The development of the geologic time scale was done after scientists witnessed certain modifications in the fossils that took place from the oldest to the newest sedimentary rocks. The phenomenon of relative dating was used to differentiate the past of the Earth in many parts of time when the same organism was there on Earth.