However, as with all searches for truth in science, facts should be supported by multiple lines of evidence.
Thus, determining the age of the Earth with alternative techniques could serve to strengthen the conclusions that have been reached with radioisotope dating methods.
Older literature divides the Tertiary into epochs (from oldest to newest): Paleocene, Eocene, Oligocence, Miocene, and Pliocene.
Moreover, the Quaternary is sometimes divided into Pleistocene and Holocene.
This geological time scale is based upon Harland , 1990, but with the Precambrian/Cambrian boundary modified according to the most recently-published radiometric dates on that interval, revising the boundary from 570 -15 million years to 543 -1 million years ago (Grotzinger , 1995).
Other changes have been proposed since 1990 (e.g., revision of the Cretaceous by Obradovich, 1993), but are not incorporated because they are relatively small.
The time scale is depicted in its traditional form with oldest at the bottom and youngest at the top -- the present day is at the zero mark.
Geologic time is finely subdivided through most of the Phanerozoic (see Harland , 1990 for details), but most of the finer subdivisions (e.g., epochs) are commonly referred to by non-specialists only in the Tertiary.
These studies may involve both qualitative and quantitative observations.
Qualitative (topological) treatments of geological time are ultimately connected to quantitative (metric) treatments.
Because of continual refinement, none of the values depicted in this diagram should be considered definitive, even though some have not changed significantly in a long time and are very well constrained (e.g., the Cretaceous/Tertiary boundary has been at 65 -1 Ma for decades, and has been tested innumerable times, with almost all dates somewhere between 64 and 66 million years).