1. Geologic Eons, Eras, and Periods
Eons are divided into eras, which are in turn divided into periods.

2. A Brief History of Earth

4. Eons Precambrian and Phanerozoic
Eon goes back to the Greek aiōn, "age." An age is not easy to measure, and neither is an eon. Both are just really long periods of time, but in science an eon is about a billion years.

5. Eras
Eons are subdivided into 7 Eras: Hadean, Archean, Cambrian, Proterozoic, Paleozoic, Mesozoic, and Cenzoic
Historical eras are defined by certain historical events or a distinctive period of time based upon the geologic and fossil record.

6. Periods
Eras are again subdivided further based upon the geologic and fossil record into periods (about 20 or s0).

7. Hadean Era

8. Hadean Era Cont.
The nature of the Hadean period of the earth's history has generally been believed to be a turbulent time of extreme heat and volatile gravitational collapse. In fact, it got its name from the images we generally hold of Hades, the mythological underground.
Heavier particles drew together through gravitational force until nuclear fusion set it ablaze in light and heat. This, of course, was the birth of our sun and solar system etc.

9. Archaean Era
Sorry no drawings could be found….no one wants to guess what the earth looked like during this era….
Probably just some sort of primordial soup of weird bacteria with a lot of destructive geologic activity this was the best I could do !

10. Archaean Era cont.
The Archaean Era was a time of continent building and the first stages of early life. About 70% of our continental land masses were formed during this Era.
The atmosphere had no oxygen (O2). Instead it would have been filled with:
Hydrogen (H2)
Methane (CH4)
Ammonia (NH3)
One type of bacteria present would have been Cyanobacteria or blue-green algaes or autotrophs (get their energy from the sun).

11. Proterozoic Era

12. Proterozoic Era Cont.
In the Proterozoic Era, the fiery formation processes of the Hadean and the continent building of the Archaen are now replaced with plate tectonics.
A single super continent is formed called Rodinia.
The atmosphere now contained oxygen (O2) and some autotrophs developed into a new type of cell called a eukaryote.

13. Proterozoic Era Cont. Eukaryotes are cells that contain a nucleus.
Living organisms were able to join together in groups to begin to form the first multi-cellular organisms.

14. Paleozoic Era

15. Paleozoic Era Cont.
The Paleozoic Era is the beginning of an explosion of new life forms in the ancient land and seas.
These new life forms included Trilobites, Brachiopods, Mollusks, Giant Insects, Tetrapods, and the first reptiles just to name a few.

16. Paleozoic Era Cont.
Near the end of the Paleozoic Era was an event called the Permian mass extinction.
At this time about 95% of all living things became extinct.
The exact cause of the extinction is debatable but it is believed to have happened over a long period of time.

17. Mesozoic Era

18. Mesozoic Era cont.
Life recovered from the Permian Extinction and took most of the first and second (Triassic and Jurassic) periods for species to evolve and recover.
The Mesozoic Era is often referred to as the ‘age of dinosaurs’.
It is estimated that there were around species of dinosaurs.

19. Mesozoic Era cont.
The warmer and drier conditions of the Mesozoic required plants to evolve and further develop with the first flowering plants appearing in the Cretaceous period.
When paleontologists discover a dinosaur leg bone, they can usually estimate how large the animal was. But when scientists uncover a fossilized leaf, it's difficult to know the size of the whole plant. To re-create ancient plants, researchers typically turn to modern plants for clues on size and appearance.

20. Mesozoic Era cont.
And then ……

21. Cenzoic Era The Cenozoic Era is known as the "Age of Mammals."
In the Paleogene Period, rodents, small horses were common and rhinoceroses and elephants first appeared.
The Neogene Period gave rise to early primates, which included early humans

22. Cenzoic Era cont.
The Cenozoic is also known as the ’Age of Mammals’, because of the large mammals that dominated. The extinction of  dinosaurs  allowed the mammals and birds to greatly diversify and become predominant.

23. Cenzoic Era cont. Today Earth's atmosphere is made of: 78% nitrogen,
21% oxygen,
0.9% argon,
0.03% carbon dioxide

24. And The Cenzoic Era is Still Continuing!

26. Clock of Eras
Using the linear time line of Geologic Time, construct a pie chart (or Clock of Eras).
Some items are already filled in for you.
You will need to write the Era’s on both the table and label them on the Clock.
Estimate the Clock time as close as you can.
From the lecture and the linear time line, can you provide a reason for a change in the historical event (in can be geologic, an extinction, or an increase or change in major species etc.)?
Clock of Eras