Resources
Geologic Timescale

GSA Geologic Time Scale

Version 6.0
Updated October 2022

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The Geological Society of America Geologic Time Scale shows color-coded time divisions based on the rock record of Earth. Cenozoic, Mesozoic, Paleozoic, and Precambrian eons are subdivided into Periods, which are then subdivided into Epochs and Ages.

Read about the changes to v. 4.0 (2012):

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