The geologic time scale is a record of the major events and diversity of life forms present in Earth's history. The geologic time scale began when Earth was formed and goes on until the present. It divides Earth's long history into units of time.
Using clever detective skills, geologists created a calendar of geologic time. They call it the Geologic Time Scale. It divides Earth’s entire 4.6 billion years into 2 major eons. Unlike months in a year, geologic time periods aren’t equally long. That’s because Earth’s timeline of natural change is episodic. That means changes happen in spurts, rather than at some slow and steady pace like a clock.
Units of Geologic Time
Geologists divide the time between Precambrian and the present into three long units called eras (Paleozoic, Mesozoic, Cenozoic).
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Topic Tips
- Eons > Eras > Periods > Epochs