Question

How were divisions of time separated when scientists created the geologic time scale?

Answer 1

The largest defined unit of time is the supereon, composed of eons. Eons are divided into eras, which are in turn divided into periods, epochs and ages. The terms eonothem, erathem, system, series, and stage are used to refer to the layers of rock that correspond to these periods of geologic time in earth's history.

http://en.wikipedia.org/wiki/Geologic_time_scale

hope that answers that for you

Answer 2

Thanks!