Earth’s History

1. Earth’s History

2. The Origins of Life • Evidence suggests that all life originated in the oceans. • The first self-sustaining molecules may have formed deep below the layers of ice near hydrothermal vents.

3. The Origins of Life 1953 – Stanley Miller

4. The Origins of Life • Recent research now suggests that simple organic compounds were brought to Earth on comets, meteors, and asteroids which crashed into the Earth during its birth.

5. Origins of life – 3 Easy Steps! • Make organic molecules (see Miller) • Replicate self • Metabolism Minerals from Black Smokers; bacteria chemosynthesize minerals; tube worms eat bacteria

6. The geologic time scale

7. 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

8. 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

9. Precambrian shields

10. Precambrian era • Earth's atmosphere • Primitive atmosphere formed from volcanic gases • Water vapor condenses and forms primitive oceans as Earth cools

12. What caused the change in the composition of our atmosphere? 1. “Locking” up of CO2 into rocks (such as limestones) 2. Development of the first “plants”

13. 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

14. Precambrian era • Achaean Era • Chemical signs of life • Prokaryotes – single celled organisms with no membrane around the “nucleus”

15. Precambrian era • Oldest fossils are cyanobacteria from NW Australia and are 3.4 – 3.5 b.y.o • Stromatolites are colonial structures formed by photosynthesizing cyanobacteria and other microbes

16. Modern stromatolites, Shark’s Bay Australia, and a 2.2 billion year old fossil stromatolite from Michigan

17. Precambrian era • Proterozoic Era • Eukaryotes – cells with a nucleus and organelles • Developed after the development of free O2 in the atmosphere

18. 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

19. The geologic time scale

20. 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

21. 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

22. Reconstruction of Earth in early Paleozoic time

23. Paleozoic era • Early Paleozoic life • Restricted to seas • Vertebrates had not yet evolved • First organisms with hard parts, such as shells – perhaps for protection

24. Paleozoic era • Life consisted of several invertebrate groups • Trilobites • Brachiopods • Cephalopods tribobite Waptia fidensis, soft-bodied arthropod

25. Appearance and relative abundance of major groups of organisms

26. 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

27. Formation of Pangaea in late Paleozoic time

28. 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

29. 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

30. Mesozoic era • Mesozoic history • North American plate began to override the Pacific plate • Mountains of western North America began forming

31. Reconstruction of Earth in the late Jurassic period

32. Mesozoic era • Mesozoic life • Survivors of the great Paleozoic extinction • Gymnosperms become the dominant trees

33. 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

34. Mesozoic era • Mesozoic life • One group of reptiles led to the birds

35. Mesozoic era • Mesozoic life • Many animal groups become extinct at the close of the Mesozoic

36. The Chicxulub impact event

37. 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

38. Cenozoic era • North America • Most of the continent was above sea level throughout the Cenozoic era • 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

39. 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)

40. 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 • Development of the San Andreas Fault (35 mya)

41. Formation of the San Andreas Fault Zone

42. Cenozoic era • Cenozoic life • 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

43. Cenozoic era • Cenozoic life • Mammals replace reptiles as the dominant land animals • Two groups of mammals evolve after the reptilian extinctions at the close of the Mesozoic • Marsupials • Placentals

44. 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