Who explained that the geological process seen happening on the earth now have shaped earth's geological features over long periods of time?
How did the statement in Lyell's principles of geology that geological features could be changed over long periods of time influence Darwin's own concept of evolution?
The longest periods of the geological time scale are eons. Each eon is divided into eras and each era is made up of periods, which are further divided into epochs. Each division ended when a significant geological event occurred, such as a major ice age ending or a meteor impact resulting in a mass extinction of animal life, etc.