Why do the major divisions of geologic time eras periods epochs span different durations if all are expressed in years?
Geologic time is based on the history of flora, fauna, and extinction events, not specific numbers of set years.
What was used by goelogists to define the beginnings and ends of the divisions of the geologic time scale?
What information does the geologic time scale provide and what are the major divisions of geological time?
The divisions of the geologic time scale are divided into four eras. from earliest to closer to the present is the Precambrian, Paleozoic, Mesozoic, Cenozoic. During these time periods, there were several major evolutionary events. Most commonly known are the dinosaurs and humans. Hope that helped :)