Weathering

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Assignments

Chernicoff, Chapter 5, "Weathering."

Reminders

Do the reading! Expect to spend at least an hour preparing for every class by reading the assigned texts--not counting review time and homework time. Do we need to schedule a special tutorial session to review the chemistry facts and principles explained in chapter 2? If you understand the focus questions on the Minerals DWG then your grasp of chemistry is sufficient for this course. If not, then we need to do better, but we cannot devote class time to it. A key to those focus questions will be posted in class on Monday. Let me know if you would attend a review session by email or in class on Monday. Possible times: Monday, Wednesday or Friday of next week from 4 to 5?

(I've forgotten the name of this poet... Can anyone identify him or her?)

Reading Focus Questions

Read the entire chapter. Focus your attention on the following questions. Be prepared to answer any of these questions should they occur on a quiz or on the final exam. For multiple choice questions select the single best answer. (Parenthetical notes are my remarks of related facts not found in the textbook.)

1. True or False? Mechanical weathering makes rocks more susceptible to chemical weathering.

    

2. The fastest, most effective type of mechanical weathering is __________ _____________.
   • (Note: rock rubble formed by this process on mountains is called "talus.")

    

3. Explain how Cleopatra's needle became subjected to increased weathering when transported from Egypt to New York. (Cf. question 2 of "For Further Thought" on p. 105.)

    

4. Mechanical exfoliation is a weathering process that results from:
   1. dissolution
   2. high temperatures
   3. abrasion
   4. pressure changes in rock layers
   • (Note: Quarry workmen sometimes hear a loud popping sound after stone is removed due to this process, also known as "sheeting.")

    

5. True or False? The breaking of rock by the growth of tree roots is a form of chemical weathering.

    

6. True or False? The dissolution of limestone by carbonic acid is part of a chemical weathering process.

    

7. Carbonic acid (H₂CO₃) is formed by the combination of:
   1. carbon with metal ions
   2. carbon with water
   3. hydrogen with carbon
   4. water with carbon dioxide

    

8. Iron oxides, or rusts, are:
   1. formed by dissolution in water
   2. formed by hydrolysis
   3. very stable on the Earth's surface
   4. easily dissolved in water

    

9. Kaolinite, a clay mineral used as the active ingredient in Kaopectate, forms from hydrolysis of potassium _______________.

    

10. True or False? Smectite, a clay mineral used in cat litter, is derived from micas.

     

11. True or False? The colder and drier a region, the less chemical weathering would occur.

     

12. How do earthworms contribute to weathering?

     

13. True or False? In general, our most valuable minerals, especially the metals, occur in pure form in nature.

     

14. Chemical weathering that makes angular boulders round is called:
    1. spheroidal weathering
    2. erosion
    3. abrasion
    4. tumbling
    5. mechanical exfoliation

     

15. True or False? Regolith ("rock blanket") is another term for bedrock.

     

16. True or False? Regolith may be 200 feet deep in places where extreme weathering has occurred.

     

17. True or False? If it were not for the process of weathering and erosion, the Earth would have no soil.

     

18. True or False? The rate of erosion constrains future agricultural productivity.

     

19. Sandstone produces poor soil because:
    1. quartz is weathering-resistant
    2. sandstone is rarely exposed to weathering agents
    3. weathering by oxidation typically produces poor soil
    4. weathering by dissolution typically produces poor soil

     

20. Skip from "Climate" on p. 99 to "Classifying Soils" on p. 102. Skip Table 5-1 on p. 103.

     

21. ______________ weathering does not occur on the Moon because it lacks an atmosphere.

     

22. True or False? The temperature of Venus is so high that little chemical weathering can occur.

     

23. True or False? The temperature of Mars is so cold that little chemical weathering occurs today.

     

24. Mars is the "red planet" because of past chemical weathering due to:
    1. oxidation
    2. dissolution
    3. hydrolysis
    4. flooding in stream channels

Class Agenda

• Review suggestions for journal geology reflections.

   

• Time, time, time. Moses wrote: "Teach us to numer our days aright, that we might gain a heart of wisdom." (Psalm 90.12) Under the sun nothing lasts forever, not even rocks and mountains. To reflect on the meaning of time, both geologically speaking and for human life, one could hardly do better than visit a cemetery with sufficient leisure for observation and reflection.
  • Study Figure 5-8. (Compare question 5 of "For Further Thought" on p. 105.)
  • What evidences of geological weathering would you look for in a cemetery?
  • Why would a cemetery be an especially good place to document rates of weathering?
  • What kind of stone would you choose for your own grave marker?
  • What would you write as your epitaph?