Unit 4: Rock Cycle and Plate Tectonics Text Questions
Assignment 1:
Read Chapter 3, Rocks: Materials of the Solid Earth, p. 52-54. Pay particular attention to the rock cycle
picture on p. 54.
1. Give a scenario where a rock might travel along this pathway: magma  igneous  metamorphic 
sedimentary  igneous. Give a reason why it might move from one rock type to another for each change.
Skim the igneous rock section, p. 55-62. Answer the following questions:
2. What is the difference between magma and lava?
3. Define extrusive or volcanic.
4. Define intrusive or plutonic.
5. How can you tell from crystal size whether a rock is extrusive or intrusive?
6. Define felsic. What common igneous rock is felsic in composition?
7. Define mafic. What common igneous rock is mafic in composition?
Skim the sedimentary rock section, p. 62-68. Answer the following questions.
8. What two processes transform sediment into a sedimentary rock?
9. What is a detrital sedimentary rock and how do they form?
10. What is a chemical sedimentary rock and how do they form?
11. If you are looking at a rocky cliff face, what feature will most likely inform you that the cliff is made of
sedimentary rock?
Skim the metamorphic rock section, p. 70-72. Answer the following questions.
12. What does metamorphism mean?
13. Define contact or thermal metamorphism.
14. Define regional metamorphism.
15. What are the two main driving forces behind metamorphism.
Assigment 2:
Read Chapter 7: Plate Tectonics, p. 194-211. Answer the following questions.
1. What was the prevailing idea about continents prior to the 1960s?
2. What are the 4 lines of evidence used by Wegener to support the continental drift hypothesis? Give a specific
example that supports each line of evidence.
3. Why was the scientific community so skeptical of Wegener’s hypothesis? What was the primary reason why
they felt the hypothesis could not be true?
4. What 3 discoveries/observations made about the sea floor in the post WWII era led to the plate tectonics
theory?
5. Why are divergent plate boundaries also called “constructive margins”?
6. List 4 facts that characterize oceanic ridge systems.
7. What is the average rate of sea floor spreading today?
8. Briefly describe the process of continental rifting, and give an example of where it is occurring today, and an
example of where it occurred in the past.
9. Why are convergent plate boundaries also called “destructive margins”?
10. Explain why the rate of lithosphere production must roughly balance the rate of lithosphere destruction.
11. Why do oceanic plates subduct at different angles? Give a location where the subduction angle is shallow,
and another where it is steep. How does this relate to where are the deepest oceanic trenches are found?
12. Compare/contrast a continental volcanic arc with a volcanic island arc. List at least 3 similarities with how
they are formed and/or features found at these location. What is the major difference between these arcs?
13. Why do extremely large mountain chains form at continent-continent convergent boundaries? Why are
there generally no volcanoes in these mountains? Give 3 examples of mountains created this way.
14. What are transform faults? Where are most transform faults located, and what features do they typically
connect?
Assigment 3:
Read Ch 7: Plate Tectonics: A Scientific Revolution Unfolds, p. 211-221. Answer the following questions.
1. What is the age of the oldest sediments recovered by deep ocean drilling? How do the ages of these
sediments compare to the ages of the oldest continental rocks? Why is this evidence for plate tectonics?
2. What is a hot spot and what creates it?
3. What happens to the age of islands or sea mounts as you move away from the current location of volcanism,
and how are these hot spot tracks evidence for plate tectonics?
4. Why did scientists originally think that the magnetic north pole wandered over time? What was actually
happening?
5. What are magnetic reversals? How do they relate to mid-ocean ridges, and how is this evidence for the plate
tectonic theory?
6. Briefly describe how hot spot tracks can be used to determine the rate of plate motion.
7. Refer to figure 7.32 and determine the three plates that appear to exhibit the highest rates of motion.
8. Describe slab pull and ridge push. Which of these forces contributes more to plate motion?
9. What role are mantle plumes thought to play in the convective flow of the mantle?
10. Briefly describe the 2 models proposed for mantle-plate convection. What is lacking in each of these
models?