Geologic time scale
Geissman, John W. Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico.
Palmer, Allison R. Institute for Cambrian Studies, Boulder, Colorado.
Last reviewed:November 2019
Show previous versions
- Geologic time scale, published March 2016:Download PDF Get Adobe Acrobat Reader
- Geologic time scale, published June 2014:Download PDF Get Adobe Acrobat Reader
- Relative time scale
- Faunal succession
- Absolute time scale
- Carbon-14 dating
- Estimates and refinements
- Related Primary Literature
- Additional Reading
An ordered, internally consistent, internationally recognized sequence of time intervals, each distinct in its own history and record of life on Earth, including the assignment of absolute time in years to each geologic interval. The geologic time scale (see illustration) has two essential components: a relative scale, consisting of named intervals of geologic history arranged in chronologic sequence from oldest (bottom) to youngest (top); and a numerical (or absolute) time scale, providing estimates of absolute ages for the boundaries of these intervals.
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