1. Edward J. Tarbuck & Frederick K. Lutgens
Earth Science, 10e
Edward J. Tarbuck & Frederick K. Lutgens

2. Earth’s History: A Brief Summary Chapter 11
Earth Science, 10e
Stan Hatfield and Ken Pinzke
Southwestern Illinois College

3. Precambrian era 4.5 billion to 540 million years ago
88% of Earth's history
Only sketchy knowledge
Most Precambrian rocks are devoid of fossils

4. Precambrian era Precambrian rocks Most are buried from view
Each continent has a "core area" of Precambrian rocks called a shield
Extensive iron ore deposits
Absent are fossil fuels

5. Precambrian shields

6. Precambrian era Earth's atmosphere
Primitive atmosphere formed from volcanic gases
A process called outgassing
Water vapor, carbon dioxide, nitrogen, and several trace gases
Very little free oxygen
Water vapor condenses and forms primitive oceans as Earth cools

7. Precambrian era Earth's atmosphere Bacteria evolve
Plants evolve and photosynthesis produces oxygen
Oxygen content in the atmosphere increases
By about 4 billion years after Earth formed, abundant ocean-dwelling organisms that require oxygen existed

8. Precambrian era Precambrian fossils Most common are stromatolites
Material deposited by algae
Common about 2 billion years ago
Microfossils of bacteria and algae have been found in chert
Southern Africa (3.1 billion years of age)
Lake Superior area (1.7 billion years of age)

9. Precambrian era Precambrian fossils
Plant fossils date from the middle Precambrian
Animal fossils date from the late Precambrian
Diverse and multicelled organisms exist by the close of the Precambrian

10. The geologic time scale

11. Paleozoic era 540 million years ago to about 248 million years ago
First life forms with hard parts
Abundant Paleozoic fossils
Early Paleozoic history
Southern continent of Gondwanaland exists

12. Paleozoic era Early Paleozoic history North America A barren lowland
Seas move inland and recede several times and shallow marine basins evaporate leaving rock salt and gypsum deposits
Taconic orogeny, a mountain building event, affects eastern North America

13. Reconstruction of Earth in early Paleozoic time

14. Paleozoic era Early Paleozoic life Restricted to seas
Vertebrates had not yet evolved
Life consisted of several invertebrate groups
Trilobites
Brachiopods
Cephalopods
First organisms with hard parts, such as shells – perhaps for protection

15. Natural cast of a trilobite

16. Appearance and relative abundance of major groups of organisms

17. Paleozoic era Late Paleozoic history Supercontinent of Pangaea forms
Several mountain belts formed during the movements of the continents
World's climate becomes very seasonal, causing the dramatic extinction of many species

18. Formation of Pangaea in late Paleozoic time

19. Paleozoic era Late Paleozoic life Organisms diversified dramatically
Land plants
Fishes evolve into two groups of bony fish
Lung fish
Lobe-finned fish which become the amphibians
Insects invade the land
Amphibians diversify rapidly
Extensive coal swamps develop

20. Mesozoic era 248 million years ago to about 65 million years ago
Often called the “age of dinosaurs”
Mesozoic history
Begins with much of the world's land above sea level
Seas invade western North America
Breakup of Pangaea begins forming the Atlantic Ocean

21. Mesozoic era Mesozoic history Mesozoic life
North American plate began to override the Pacific plate
Mountains of western North America began forming
Mesozoic life
Survivors of the great Paleozoic extinction
Gymnosperms become the dominant trees

22. Reconstruction of Earth in the late Jurassic period

23. Mesozoic era Mesozoic life
Reptiles (first true terrestrial animals) readily adapt to the dry Mesozoic climate
Reptiles have shell-covered eggs that can be laid on the land
Dinosaurs dominate
One group of reptiles led to the birds
Many reptile groups, along with many other animal groups, become extinct at the close of the Mesozoic

24. Major reptile groups in the Mesozoic era

25. Mesozoic era Mesozoic life
Many reptile groups, along with many other animal groups, become extinct at the close of the Mesozoic
One hypothesis is that a large asteroid or comet struck Earth
Another possibility is extensive volcanism

26. Cenozoic era 65 million years ago to the present
Often called the “age of mammals”
Smaller fraction of geologic time than either the Paleozoic or the Mesozoic
North America
Most of the continent was above sea level throughout the Cenozoic era

27. Cenozoic era North America
Many events of mountain building, volcanism, and earthquakes in the West
Eastern North America
Stable with abundant marine sedimentation
Eroded Appalachians were raised by isostatic adjustments

28. Cenozoic era North America Western North America
Building of the Rocky Mountains was coming to an end
Large region is uplifted
Basin and Range Province formed
Re-elevates the Rockies
Rivers erode and form gorges (e.g., Grand Canyon and Black Canyon)

29. Cenozoic era North America Western North America
Volcanic activity is common
Fissure eruptions form the Columbia Plateau
Volcanoes form from northern California to the Canadian border
Coast Ranges form
Sierra Nevada become fault block mountains

30. Cenozoic era Cenozoic life
Mammals replace reptiles as the dominant land animals
Angiosperms (flowering plants with covered seeds) dominate the plant world
Strongly influenced the evolution of both birds and mammals
Food source for both birds and mammals

31. Cenozoic era Cenozoic life
Two groups of mammals evolve after the reptilian extinctions at the close of the Mesozoic
Marsupials
Placentals

32. Cenozoic era Cenozoic life
Mammals diversify quite rapidly and some groups become very large
e.g., Hornless rhinoceros, which stood nearly 16 feet high
Many large animals became extinct
Humans evolve

33. End of Chapter 11