Assignment 6: Volcanoes and other Mountains
Geology 110: Earth and Space Science
Homework
SELF-REFLECTION AND COMPREHENSION SURVEYS
Checkpoint 6.1, p. 149
#1: Place the following 4 materials--maple syrup, milk, peanut butter, frozen yogurt--in
the correct position (A, B, C, D) for their relative viscosity.
A:
B:
C:
D”
Checkpoint 6.3, p. 150
#2: How would you classify the viscosity of the magma that produced the eruption of
Nyiragongo and the violence of the eruption itself?
a. Low-viscosity magma; violent eruption b. High-viscosity magma; violent eruption
c. High-viscosity magma; mild eruption d. Low-viscosity magma; mild eruption
Checkpoint 6.5, p. 151
#3: In addition to the chocolate chip cookie analog, describe another common example or
common material or object that models the partial melting of minerals with different
silica contents.
Checkpoint 6.8, p. 153 (Optional extra credit; must complete all questions to be
considered for extra credit)
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#4: Go to www.volcano.si.edu/reports/usgs/ to obtain the Smithsonian/USGS weekly
volcanic activity report. Click on the world map link and compare the location of each
volcano with a map of plates (Fig. 4.21) to predict the type of magma generated at each
location.
a. Write a one-sentence summary for each location to describe the volcanic activity
(including magma type)
b. Is there any relationship between the type of activity at each volcano and the plate
tectonic setting?
Checkpoint 6.9, p. 154
#5: Predict the type of magma associated with Mt. St. Helens.
a. Andesitic
b. Basaltic
c. Rhyolitic
Checkpoint 6.10, p. 155
#6: Earthquakes and Mount St. Helens
Volcanic eruptions are often preceded by earthquake activity as magma rises upward
through the crust underlying the volcano. Examine the graphs of earthquake events for 1980
(graph a) and for 1981-1991 (graph b). How did earthquake activity differ for the two
intervals?
Checkpoint 6.13, p. 162
#7: Trees were knocked down up to 27 kilometers (17 miles) from Mount St. Helens by
the blast associated with the eruption. Where would a volcano in your region be if it were
27 kilometers from your home or college?
Checkpoint 6.15, p. 166
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#8: Compare and contrast the consequences of a major earthquake and a volcanic
eruption with a VEI of 5. Imagine that you were mayor of a city that was located within
30 kilometers of the epicenter or volcano and that you had evacuated the residents prior
to the earthquake or eruption. Which aftermath would you prefer deal with and why?
Checkpoint 6.16, p. 167
#9: Read the following description of the eruption history of Mount Shasta and answer
the questions that follow.
Mt. Shasta Volcanic History
Mount Shasta in northern California is a stratovolcano consisting of overlapping cones centered
at four main vents. Eruptions produced andesite lava and pyroclastic flows. During the last
millennium, Mount Shasta has erupted on the average at least once every 250 years. The most
recent eruption occurred in 1786 A.D.
Lava flows issued from vents near the summit and from vents on the slopes of the volcano.
Individual lava flows are up to 13 kilometers (8 miles) long. No lava flows extended for more
than 20 kilometers (12 miles) from the summit.
Pyroclastic flows from the summit and the Shastina vent (see map) have traveled distances of
more than 20 kilometers. Other vents produced flows that extended up to 10 kilometers.
Eruptions from the summit crater produced lahars that reached more than 20 kilometers and
spread out around the base of the volcano. The largest lahars entered the McCloud and
Sacramento Rivers.
Tephra deposits cover the ground within about 25 kilometers (16 miles) of the summit. A massive
debris avalanche occurred around 300,000 years ago. The debris avalanche flowed more than 64
kilometers (40 miles) through the Shasta valley and covered more than 675 square kilometers
(260 square miles).
After reviewing the volcanic history of Mount
Shasta and examining the map of the vicinity,
identify potential volcanic hazards for the area
surrounding Mount Shasta. Remember that the
eruption styles and products of future events will
be similar to those of historical eruptions.
1. Show the possible extent of selected hazards on
the map of Mount Shasta and vicinity.
2.
Evaluate whether the cities of Weed, Mount
Shasta City, McCloud, and Dunsmuir will face
the same types of hazards from a future eruption
of Mount Shasta. Which city is most at risk?
Explain your choice.
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Checkpoint 6.17, p. 169
#10: What type of volcano is Mt. St. Helens?
a. Shield volcano
b. Stratovolcano
c. Cinder cone
Checkpoint 6.18, p. 169: Decade Volcanoes, Part II
#11: Answer the following questions using the volcanoes illustrated on the map in
Checkpoint 6.7 (page 153). It may be useful to review a map of plate boundaries in
Chapter 4 (see Chapter 4 Snapshot) before attempting to answer the questions.
1. Most of the volcanoes on this map are:
a) shield volcanoes b) stratovolcanoes
c) cinder cone volcanoes
2. Name a stratovolcano not associated
with the subduction of the Pacific Plate.
3. Name a shield volcano.
Checkpoint 6.19, p. 169
#12: Venn Diagram (not provided; see page 169 for Venn Diagram): Shield Volcanoes,
Stratovolcanoes, and Cinder Cones
Compare and contrast the three principal types of volcanoes.
1. Associated with subduction zones
2. Have a triangular shape in profile
3. Example: Mount Hood, Oregon
4. Mild eruptions
5. High-silica magma
6. Smallest volcanoes
7. Largest volcanoes
8. Explosive eruptions
9. Composition mainly tephra
10. Form chains of volcanic islands
11. Pose greatest hazards
12. Vent gases
13. Example: Mauna Loa
14. Found in continental U.S. and Alaska
15. Found in Hawaii
16. Main product--lava
17. Low silica magma
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18. Intermediate silica magma
19. Principal rock type--basalt
20. Principal rock type--andesite
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Checkpoint 6.28, p. 177
#13: Draw a concept map that illustrates how the erosion of the Himalayas resulted in a
decrease in global temperatures.
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