Sci. 3-5

Times Marches On

Pages 73-77

A.The history of the Earth is recorded in rock layers

1) Earth is about 4.6 billion years old.

B.The geologic time scale- a scale that divides Earth’s 4.6 billion year history into distinct intervals of time.

C. Eons- largest division of time

1) Hadean Eon

2) Archean Eon

3) Proterozoic Eon

4) Phanerozoic Eon

D.Eras- the eons are divided into eras.

1)Phanerozoic Eon has 3 eras.

a) Paleozoic- no land animals at the beginning, mostly water animals, toward the end- some land animals and amphibians and insects.

b) Mesozoic- Age of the Reptiles- Dinosaurs, some small mammals and birds

c) Cenozoic- recent life- Age of mammals, humans show up here.

E. Periods- Eras are divided into Periods.

1)Paleozoic has 7 Periods.

2) Mesozoic has 3 Periods.

3) Cenozoic has 2 Periods.

F. Epochs- Cenozoic has the periods divided into epochs because we have some much information about this Era.