1. Geologic Time Scale
Spring 2015
8th Grade

2. Geologic Time Scale
The geologic time scale is a record of the major events and diversity of life forms present in Earth’s history.
The geologic time scale began when Earth was formed and goes on until the present.
At the end of each era a mass extinction occurred, many kinds of organisms died out, although there were other extinctions going on during each period of geologic time.
Using the fossil record, paleontologists have created an idea of the different types of common organisms in each geologic period.

3. Divisions of Geologic Time
Eras are subdivided into periods...periods are subdivided into epochs.
Era
Period
Epoch
E + P = EP

4. Divisions of Geologic Time
Various models, diagrams, and pictures can be used to illustrate the vastness of time involved in and to show the diversity of life evident across geologic time.

5. Cretaceous- Flowering Plants, Major extinction of Dinosaurs
Jurassic- Early birds & Mammals, abundant dinosaurs
Triassic- Lots of Conifers, 1st Dinos, 1st Mammals
Mesozoic Era

6. Paleozoic Permian- Mass Extinction of marine animals like trilobites
Devonian – Early trees
Silurian- Early land plants
Ordovician- Early Fish
Paleozoic

7. Precambrian Proterozic- Single→Multicellular
Organisms.
Archean– Oldest fossils, bacteria & sinlge celled organisms
Precambrian

8. Precambrian Era 88% of the History of Earth
4.6 Billion Years Ago – 450 Million Years Ago
(Color in 27 wedges)

9. Precambrian Era Earth's first era of time.
5 major events occurred during this era:
(1) the formation of the Sun and light
(2) the creation of the Earth
(3) the creation of the atmosphere through volcanic out-gassing
(4) the creation of the oceans
(5) the creation of life

10. Precambrian Era
Began with simple life forms such as bacteria and simple algae.
There was a rise of simple organisms such as jellyfish and sea worms by the end of the era.
Few fossils because the life forms were soft-bodied and had no hard skeleton.

11. Precambrian Era Geological Events: Earth Began Biological Events:
Bacteria Appear
Soft-Bodied Multi-Cellular Organisms Appear

12. Paleozoic Era 544 Million Years Ago – 244 Million Years Ago
Ancient Life
544 Million Years Ago – 244 Million Years Ago
(Color in 3 wedges)

13. Paleozoic Era Animal Life:
Began with the early invertebrates, such as trilobites and brachiopods.
Continued to develop early vertebrate fish, arachnids and insects.
Later came the first amphibians and near the era’s end the reptiles became dominant.

14. Paleozoic Era Plant Life:
Early land plants included simple mosses, ferns, and then cone-bearing plants.
By the end of the era, seed plants were common.
The mass extinction that ended the era caused most marine invertebrates as well as amphibians to disappear.

15. Paleozoic Era Geological Events: Biological Events:
Shallow seas cover much of the land
Coral reefs develop
Pangaea forms
Appalachian Mountains form
Biological Events: 
Great explosion of invertebrates in the sea (Trilobites appear)
Land plants appear
Insects and spiders appear
Age of fish begins
First reptiles appear
Trilobites become extinct

16. Mesozoic Era 245 Million Years Ago – 65 Million Years Ago Middle Life
(Color in 1 ½ wedges)

17. Mesozoic Era
Reptiles were the dominant animals of this era, including the various dinosaurs.
Small mammals and birds also appeared.
Toward the end of the era, flowering plants appeared and the kinds of mammals increased.
The mass extinction that ended the era caused the dinosaurs to become extinct.

18. Mesozoic Era Geological Events: Hot, dry conditions dominate Pangaea
Pangaea splits
Widespread volcanic activity
Biological Events:
Dinosaurs appear
Largest dinosaurs thrive
Dinosaurs become extinct
Mammals, birds and flowering plants appear

19. Cenozoic Era 65 million years ago - Today Recent Life
(Color in a ½ wedge)

20. Cenozoic Era Many mountain ranges formed
New mammals appeared while others became extinct.
Mammals had to evolve to adapt to different environments.
The diversity of life forms increased.
Flowering plants became most common.
Humans are also part of the most recent period of this era.
Many mountain ranges formed
ex. Alps in Europe, Himalayas in India & Rocky Mountains in the USA

21. Cenozoic Era Geological Events: Rocky Mountains and Himalayas form
Continental glaciers cover Antarctica
Ice age ends
Biological Events:
First grasses appear
Mammals, flowering plants, and insects dominate the land
Humans appear