1. The fossil of one of the earliest birds, called archaeopteryx, shows reptile-like features. It lived during the late Jurassic period, about 105 my ago. Fig. 4-CO, p.72

2. Earth Rocks, Earth History and Mass Extinctions Earth Rocks, Earth History and Mass Extinctions James Hutton, uniformitarimism and the fossil record. James Hutton, uniformitarimism and the fossil record. Mass Extinctions (4.1)…large ones 248 and 65 million years ago. What caused them? Mass Extinctions (4.1)…large ones 248 and 65 million years ago. What caused them? We will look at three hypothesis for mass extinctions next. We will look at three hypothesis for mass extinctions next. To right: the red line shows the number of families of organisms has varied throughout time. What does leftward shift mean? To right: the red line shows the number of families of organisms has varied throughout time. What does leftward shift mean? Fig. 4-1, p.74

3. Fig. 4-1a, p.74

4. Fig. 4-1b, p.74

5. Fig. 4-1c, p.74

6. 1. Extraterrestrial Impacts: Most scientists agree the Cretaceous extinction was caused by a giant meteorite impact. Evidence is found in the Yucatan peninsula. It may have caused global cooling. Walter and Luis Alvarez (1977) found iridium-rich clay bed (rare on Earth but abundant in meteorites). Suggested meteorite 10 km in diameter hit the Earth (with energy 10x that of our global nuclear arsenal). Fig. 4-2, p.75

7. Evidence of meteor impact found in Caribbean Sea. Evidence of meteor impact found in Caribbean Sea. Fig. 4-2a, p.75

8. The impact would have pulverized the meteorite and rocks of the Earth’s crust creating a thick, dark cloud that caused the Earth’s surface to freeze. The impact would have pulverized the meteorite and rocks of the Earth’s crust creating a thick, dark cloud that caused the Earth’s surface to freeze. Fig. 4-2b, p.75

9. 2. Volcanic Eruptions: can cause global warming and cooling…how? 248 million years ago massive flood basalts erupted in Siberia (may have caused Permian extinction). 2. Volcanic Eruptions: can cause global warming and cooling…how? 248 million years ago massive flood basalts erupted in Siberia (may have caused Permian extinction). 3. Atmosphere-Ocean- Continent System Interactions: supercontinent assembled during Permian; no mixing from currents, CO2 level rose in sea, temperatures fell (less greenhouse gas in atmosphere), sea level fell, glaciers grew, oceans cooled at surface and eventually sank, releasing large amounts of CO2 into atmosphere. 3. Atmosphere-Ocean- Continent System Interactions: supercontinent assembled during Permian; no mixing from currents, CO2 level rose in sea, temperatures fell (less greenhouse gas in atmosphere), sea level fell, glaciers grew, oceans cooled at surface and eventually sank, releasing large amounts of CO2 into atmosphere. Fig. 4-3, p.76

10. Fig. 4-3a, p.76

11. Fig. 4-3b, p.76

12. Geologic Time How old is the Earth? How old is the Earth? When did our earliest ancestors arrive? When did our earliest ancestors arrive? Geologic time is deep time. Scientists measure time in two different ways: Relative (the order in which events occurred) and Absolute (the order and how much time has passed since they occurred). Geologic time is deep time. Scientists measure time in two different ways: Relative (the order in which events occurred) and Absolute (the order and how much time has passed since they occurred). Fig. 4-3c, p.76

13. Relative Time: The principle of original horizontality tells us that most sedimentary rocks are deposited in horizontal beds…. Relative Time: The principle of original horizontality tells us that most sedimentary rocks are deposited in horizontal beds…. If tilted…. If tilted…. Fig. 4-5a, p.79

14. …we infer that they were tilted after they were deposited …we infer that they were tilted after they were deposited…and… Fig. 4-5b, p.79

15. …folded after they formed, such as this limestone that formed 500 million years ago in a shallow sea. Four hundred million years later, tectonic forces uplifted and folded it in the Canadian Rockies, Alberta. Fig. 4-4, p.78

16. The principle of superposition states that in a sequence of sedimentary beds, the oldest bed (labeled 1) is at the bottom, and the youngest (labeled 5) is on top. Imagine the beds were tilted vertically; how could you tell which was youngest? Fig. 4-6, p.79

17. The principle of cross- cutting relationships is shown where this basalt dike cuts across sandstone in the walls of the Grand Canyon. Is the dike older or younger than the sandstone? The principle of cross- cutting relationships is shown where this basalt dike cuts across sandstone in the walls of the Grand Canyon. Is the dike older or younger than the sandstone? Fig. 4-7, p.79

18. Three dikes cutting across sedimentary rocks. What are the age relationships? Fig. 4-8, p.79

19. The theory of evolution states that life forms have changed throughout geologic time. Fossils are remains/traces of prehistoric life preserved in sedimentary rocks. What is the principle of faunal succession? How do fossils show ancient environments (like corals found at the summit of Mount Everest?)… Fig. 4-9, p.80

20. Gaps in the record: Unconformities and correlation…the walls of the Grand Canyon show sedimentary rocks lying on igneous/metamorphic rocks (age ranges from 2 billion to 200 million years). Fig. 4-10, p.80

21. A disconformity is created by uplift and erosion, followed by deposition of more sediment. The disconformity is a gap in the rock record. Fig. 4-11, p.81

22. Fig. 4-12, p.81

23. Angular unconformity… Angular unconformity… Fig. 4-13, p.82

24. Fig. 4-13a, p.82

25. Fig. 4-13b, p.82

26. Fig. 4-13c, p.82

27. Fig. 4-13d, p.82

28. Fig. 4-14, p.82

29. The rock record is full of gaps in any one place…so must correlate for a more complete record…correl ation includes time and lithologic. The rock record is full of gaps in any one place…so must correlate for a more complete record…correl ation includes time and lithologic. Fig. 4-15, p.83

30. For time correlation, use index fossils, fossil assemblages and key beds. Fig. 4-17, p.84

31. Fig. 4-16, p.84

32. Fig. 4-16a, p.84

33. Fig. 4-16b, p.84

34. Fig. 4-16c, p.84

35. Absolute Geologic Time: geologists have found a natural process that occurs at a constant rate and accumulates its own record (unstable or radioactive isotopes)… Fig. 4-18, p.85

36. Radioactive parent decays to daughter…t he half-life is the time required for half of the parent to decay to daughter. Radioactive parent decays to daughter…t he half-life is the time required for half of the parent to decay to daughter. Fig. 4-19, p.86

37. Table 4-1, p.87

38. The geologic time chart. The geologic time chart. Fig. 4-20, p.89

39. Fig. 4-21, p.90

40. Fig. 4-22, p.90

41. Fig. 4-23, p.91

42. p.92