Essential Questions

1. Three major geological events that took place on Planet Earth were the mass extinction of dinosaurs, when Pangea split, and the first time homo-sapiens appeared.

2. There are three Eras, and four Eons in Earth's history.

3. An eon is the largest unit of the geological time scale as oppose to an era which is the second largest unit of the geological time scale.

4. Scientists created eras and eons in the first place in order to have a type of measuring unit for them to be able to measure time in terms of the Earth.