Geologic Time Scales

1] What were three major geologic events in the history of the Earth?
_ humans appearing on earth
_ dinosaurs
_volcano eruptions

2] How many Eras, Eons ( periods or epochs ) are there?
_ 4 Eras , 12 Periods , 11 Epochs.

3] What do you think are the differences between Eras / Eons?
_ Eon, Era & Epoch are 3 different geochronological unities.
_ Eon is first, Era is the second, Epoch are the fourth.
_ Between an ara and an epoch there is a Period*

4] Why did scientist create Eras and Eons in the first place?
_Scientist created Eras & Eons to describe the timing and relationships between events that have occurred throughout Earth's history.