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Earth System History
Oct. 2nd, 2016 11:10 pm1. What is a Precambrian shield? Where is one located in North America?
2. What reasons are there to believe that Earth was pelted by vast numbers of meteorites early in its history?
3. Why might we expect Earth to be nearly the same age as its moon and the material that forms meteorites?
4. What geologic features characterize greenstone belts, and how did greenstone belts form?
5. What types of sedimentary rocks were rare in the Archean Eon? What does this suggest about the nature of cratons during Archean time?
6. Why did magma rise from the mantle to Earth’s surface at a higher rate during Archean time than it does today?
7. What features make Earth a more hospitable place than other planets for life as we know it?
8. Why is it likely that life arose in the vicinity of midocean ridges?
9. What are stromatolites? From what we know of their formation today, why might we expect them to
have been present early in Earth’s history?
10. What evidence is there that certain kinds of bacteria and archaea were present in Archean time?
11. Why did oxygen remain at a low concentration in the atmosphere until long after photosynthesizing cyanobacteria were very abundant on Earth?
12. The composition and configuration of Earth’s crust changed more profoundly in the course of Archean time than during any later interval of Earth’s history. Using the Visual Overview on pages 250–251 and what you have learned in this chapter, describe major changes in the Archean crust and explain how they relate to one another and to changes in Earth’s deep interior.
1. How are the basic features of the Wopmay orogen typical of orogenic belts in general?
2. What kinds of geologic evidence suggest that continental glaciers spread widely more than 2 billion years ago?
3. List as many differences as you can between the Archean world and the world as it existed 1 billion years ago.
4. What arguments favor the idea that little atmospheric oxygen existed on Earth until slightly before 2 billion years ago?
5. What evidence is there that eukaryotic organisms existed 2 billion years ago?
6. How does the history of North America illustrate continental accretion?
7. Where did the Grenville orogeny occur?
8. How were the crustal elements of Gondwanaland assembled?
9. Using a world map, locate the modern positions of the various landmasses that make up the supercontinent Nuna shown in Figure 12-22.
10. What major biological events occurred near the end of Proterozoic time?
11. What is curious about the Neoproterozoic rocks known as cap carbonates? (Hint: Refer to Earth System Shift 12-2.)
12. Life underwent extraordinary changes in the course of Proterozoic time. Using the Visual Overview on pages 276–277 and what you have learned in this chapter, describe these changes and explain how some of them may have been related to changes in the chemistry of the atmosphere.
2. What reasons are there to believe that Earth was pelted by vast numbers of meteorites early in its history?
3. Why might we expect Earth to be nearly the same age as its moon and the material that forms meteorites?
4. What geologic features characterize greenstone belts, and how did greenstone belts form?
5. What types of sedimentary rocks were rare in the Archean Eon? What does this suggest about the nature of cratons during Archean time?
6. Why did magma rise from the mantle to Earth’s surface at a higher rate during Archean time than it does today?
7. What features make Earth a more hospitable place than other planets for life as we know it?
8. Why is it likely that life arose in the vicinity of midocean ridges?
9. What are stromatolites? From what we know of their formation today, why might we expect them to
have been present early in Earth’s history?
10. What evidence is there that certain kinds of bacteria and archaea were present in Archean time?
11. Why did oxygen remain at a low concentration in the atmosphere until long after photosynthesizing cyanobacteria were very abundant on Earth?
12. The composition and configuration of Earth’s crust changed more profoundly in the course of Archean time than during any later interval of Earth’s history. Using the Visual Overview on pages 250–251 and what you have learned in this chapter, describe major changes in the Archean crust and explain how they relate to one another and to changes in Earth’s deep interior.
1. How are the basic features of the Wopmay orogen typical of orogenic belts in general?
2. What kinds of geologic evidence suggest that continental glaciers spread widely more than 2 billion years ago?
3. List as many differences as you can between the Archean world and the world as it existed 1 billion years ago.
4. What arguments favor the idea that little atmospheric oxygen existed on Earth until slightly before 2 billion years ago?
5. What evidence is there that eukaryotic organisms existed 2 billion years ago?
6. How does the history of North America illustrate continental accretion?
7. Where did the Grenville orogeny occur?
8. How were the crustal elements of Gondwanaland assembled?
9. Using a world map, locate the modern positions of the various landmasses that make up the supercontinent Nuna shown in Figure 12-22.
10. What major biological events occurred near the end of Proterozoic time?
11. What is curious about the Neoproterozoic rocks known as cap carbonates? (Hint: Refer to Earth System Shift 12-2.)
12. Life underwent extraordinary changes in the course of Proterozoic time. Using the Visual Overview on pages 276–277 and what you have learned in this chapter, describe these changes and explain how some of them may have been related to changes in the chemistry of the atmosphere.
