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10. Briefly explain how and where folded mountains form and how 3. What are the significant similarities and differences between
fault block mountains form. elastic deformation and plastic deformation?
11. The magnitude of an earthquake is measured on the Richter 4. Explain the combination of variables that results in solid rock
scale. What does each higher number mean about an layers folding rather than faulting.
earthquake?
12. Identify three areas of probable volcanic activity today in the
United States. Explain your reasoning for selecting these three INVITATION TO INQUIRY
areas.
13. Discuss the basic source of energy that produces the earthquakes Earthquake Patterns?
in southern California. Click on http://earthquake.usgs.gov/eqcenter/index.php for a list of
14. Describe any possible relationships between volcanic activity and magnitude-1 earthquakes cataloged in the last week for the United
changes in the weather. States. Earthquakes magnitude 3 and greater are in a separate list. The
15. What is the source of magma that forms volcanoes? Explain how most recent earthquakes are at the top of each list. Click on the column
the magma is generated. header for information about that column. Click on the word map to
16. Describe how the nature of the lava produced results in the three see a map displaying the location. Click on an event’s date or depth
major classification types of volcanoes. for additional information about the earthquake. Explore the loca-
17. What are mountains? Why do they tend to form in long, thin tion and magnitude of earthquakes until you can answer the following
belts? questions:
1. Do earthquakes appear to occur anywhere or mostly in specific
FOR FURTHER ANALYSIS regions?
2. Is there a recognizable pattern to where earthquakes seem to occur?
3. Is there any relationship between the earthquake locations and a
1. Evaluate the statement “the present is the key to the past” as it
represents the principle of uniformity. What evidence supports map showing tectonic plates?
this principle? 4. Examine a map that shows the types of tectonic plate boundaries
(convergent, divergent, transform). Do the deep earthquakes
2. Does the theory of plate tectonics support or not support the
principle of uniformity? Provide evidence to support your seem to correlate to any particular type of plate boundary?
answer. 5. Can you explain any patterns or correlations that you found?

PARALLEL EXERCISES

The exercises in groups A and B cover the same concepts. Solutions to group A exercises are located in appendix E.

Group A Group B
1. The rocks in an anticline have been folded into a semicircular 1. The rocks in a syncline have been folded into a semicircular
arch with a radius of curvature of 10 m. How much has the trough with a radius of curvature of 7.5 m. How much has the
folding shortened the rock layer? folding shortened the rock layer?
2. Sedimentary rocks have been folded into two semicircular 2. Sedimentary rocks have been folded into two semicircular
anticlines and a semicircular syncline. The folds have a radius of synclines and a semicircular anticline. The folds have a radius of
curvature of 54 m. How much has the folding shortened the curvature of 28 m. How much has the folding shortened the
rock layer? rock layer?
3. A horst is bounded on the east and west by two normal faults. 3. A horst is bounded on the east and west by two normal faults.
The fault plane of the west fault has a slope of 2.1 m/m to the The fault plane of the west fault has a slope of 0.89 m/m to the
west. The plane of the eastern fault slopes 2.9 m/m to the west. west. The plane of the east fault slopes 0.78 m/m to the west.
The sedimentary layers cut by the faults have been displaced The sedimentary layers cut by the faults have been displaced
105 meters. How much extension has occurred? 64 meters. How much extension has occurred?
4. The hanging wall of a fault has been displaced downward by 4. The hanging wall of a fault has been displaced upward by 154 cm
20 cm relative to the footwall, and there has been a total relative to the footwall, and there has been a total horizontal
horizontal displacement of 32 cm. What is the slope of the fault displacement of 190 cm. What is the slope of the fault and what
and what type of fault is it? type of fault is it?
5. A thrust fault with a slope of 0.176 m/m has a horizontal 5. A thrust fault with a slope of 0.0087 m/m has a horizontal
displacement of 105 m. How much vertical displacement displacement of 11.5 km. How much vertical displacement
occurred? occurred?
6. A fence was built across a strike-slip fault that is creeping at a 6. A walkway built in 1945 over a strike-slip fault had 0.85 m offset
rate of 50 mm/yr. How much will the fence be offset in 25 years? by 1992. What is the creep rate of the fault in mm/yr?

498 CHAPTER 19 Building Earth’s Surface 19-22