Chapter 2 - Early Geologic Time: The Precambrian Era 1. Why is earth unique among the planets? Give three reasons… A) B) C) 2. Summarize your idea of the origin of the earth. Why do scientists still have several theories about this? 3. What is the present theory about how the moon formed? Describe. 4. Impact craters on earth show evidence of meteorites – some rather large and destructive. List the two largest craters and their locations: A) B) What is the age of the oldest craters known? Could there be a reason that there is no evidence beyond this? Explain. What element is associated with meteoric impacts? What country is the best place to look for these? Why might this be the best place? 5. Describe the connection between plate tectonics and diamond development. 6. Describe the early atmosphere relative to present day. What was the key reason that the atmosphere changed its carbon dioxide content? 7. Why is uranium useful in radiometric age dating for older rocks, while carbon is useful for fossils? Explain. 8. You’ve just been asked to describe the significance of stromatolites and their role in the early processes of photosynthesis. Since you’ve already read page 23, what would you say? 9. Everyone knows that the dinosaurs represent a major extinction event. How many have occurred so far, and how has this affected the diversity of species on present day earth? 10. Global climate change…if you haven’t seen An Inconvenient Truth yet – go see it!!! Aside from that, give three geological reasons or theories as to why there is change in global climatic patterns.