1. Geologic Time

4. TIME
Current geologic evidence holds that the age of Earth is about 4570 million years old (4.570 billion years)
Geologic Time Scale = classification of events in the Earth’s formation
Divisions are based on events in Earth’s history such as extinction of major organisms, major climate changes, or arrival of new organisms

5. Divisions Eon- largest division of time
Eras- divide eons of time- 2nd largest time division
Periods- divide eras of time- 3rd largest time division
Epoch- divide periods of time- smallest time division

6. largest
2nd largest
3rd largest
smallest

7. EON Examples- Proterozoic and Phanerozoic
Very large divisions of time- contains hundreds or thousands of millions of years

8. ERA
Examples- *Precambrian- (refers to everything before Cambrian explosion), Paleozoic, Mesozoic and Cenozoic
2nd largest division of time
Precambrian – longest era -simplest life (bacteria and algae)
Paleozoic- simple life (invertebrates, fishes, reptiles)
Mesozoic- time of the dinosaurs, evergreens, and flowering plants
Cenozoic- mammals, humans

9. Period Examples- Tertiary and Quaternary
Both are divisions of the Cenozoic Era
3rd largest division of time
Tertiary- primates and Chesapeake Bay formed
Quaternary- period of last ice age

10. Epoch
Examples- Holocene, Pleistocene, Pliocene, etc.. (all are divisions of the Quaternary period)
Smallest division of time
Equus from Pleistocene