Assignment 6: Volcanoes and other Mountains
Geology 110: Earth and Space Science
Homework (20 points)
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.
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Checkpoint 6.8, p. 153 (Optional extra credit; must complete all questions to be
considered for extra credit-Message for online classes only: submit in your
notebook)
#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?
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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
#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 (Message for online classes only: you will need to draw on
the map, so please submit you answers to this checkpoint in your notebook during
the mid-term exam)
#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.
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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.
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.
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Checkpoint 6.19, p. 169 (Message for online classes: submit in your notebook)
#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
18. Intermediate silica magma
19. Principal rock type--basalt
20. Principal rock type--andesite
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Checkpoint 6.28, p. 177 (Message for online classes: for notebook to be turned in
during the mid-term exam)
#13: Draw a concept map that illustrates how the erosion of the Himalayas resulted in a
decrease in global temperatures.
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