Moreover, the Quaternary is sometimes divided into Pleistocene and Holocene. Good overview as relates to the Grand Canyon: References available on the department's web page.
Dinosaurs disappeared about 65 million years ago. Geologic time is often dicussed in two forms:. These subdivisions are given names, most of which can be recognized globally, usually on the basis of fossils. Earth Science Week Editor's Note: These can not be included in the diagram for practical reasons, but can be found in Harland et al.