Download Living Physical Geography Instructor`s Manual CHAPTER 14

Living Physical Geography
Instructor’s Manual
CHAPTER 14
Geohazards: Volcanoes and Earthquakes
CHAPTER SUMMARY
This chapter covers volcanoes and earthquakes, both in terms of why they occur and as major
hazards for people. There are three types of volcanoes: shield volcanoes, stratovolcanoes, and
cinder cones. Shield volcanoes are the largest volcano type and cinder cones are the smallest.
Shield volcanoes do not produce explosive eruptions and they have runny lava that flows
downslope in thin sheets. Stratovolcanoes, on the other hand, can be explosive and violent and
can produce thick, blocky lava.
Volcanoes produce lava, pyroclasts, and gases. They strongly modify Earth’s surface where
they are active. Lava thickness or viscosity depends largely on the amount of silica in the lava.
Mafic lava has a low silica content, is thin, and flows readily downslope in thin sheets.
Intermediate lava has a silica content between 50% and 70% and is thick, with a blocky texture.
Felsic lava has a silica content higher than 70% and has high viscosity.
Pyroclasts are airborne materials ejected from a volcano in an eruption. They include lapilli
and pumice, block and bombs, and ash. During an eruption, gases in the magma may rapidly
expand, creating an explosive eruption that generates pyroclasts.
Volcanic landforms include areas with columnar jointing, large igneous provinces, and
calderas. Columnar jointing is an unusual pattern of joints in rocks that forms as lava slowly
cools. Large igneous provinces are the most geographically extensive volcanic landform on
Earth. They are formed from major episodes of volcanism in which flood basalts are deposited
in layers, often over time periods of many millions of years. Calderas form as a volcano’s
magma chamber empties and collapses, forming a crater-like depression.
Volcanic eruptions are ranked using the volcanic explosivity index (VEI). Major volcanic
eruptions are VEI 6 or greater and emit 10 km3 (2.4 mi3) to 100 km3 (24 mi3) of material. Lahars
and pyroclastic flows are the two greatest threats volcanoes bring. Lahars are torrents of mud
that result as snow and ice are suddenly melted and flow downslope in stream channels.
Pyroclastic flows are searing hot gases that travel quickly down the flanks of the volcano. Both
lahars and pyroclastic flows are very dangerous to people. The greatest concentration of
dangerous stratovolcanoes occurs in the Pacific Ring of Fire.
Earthquakes are also a significant hazard to people. Earthquakes occur as the crust breaks
along a fault and releases seismic waves that travel through the crust and shake the surface.
The earthquake focus occurs where the crust breaks. Movement of the mantle below the
lithosphere generates the force that moves the lithosphere. Most earthquakes occur along
seismic belts, areas that appear along plate boundaries.
The modified Mercalli intensity scale is used to rank earth shaking based on damage done
to human-built structures. Areas closer to the earthquake focus experience more shaking and a
higher numbered ranking compared to areas far away from the focus. Scientists use
1
seismographs to measure and record earth movement during an earthquake. The moment
magnitude scale ranks earthquakes based on the amount of ground movement measured with
a seismograph. Both ground movement and energy released during an earthquake are given
with the moment magnitude scale.
The Geographic Perspectives section at the end of the chapter outlines the great eruption
of Tambora in 1815. This volcanic eruption exemplifies the potential of volcanoes to have a
global impact on people.
TEACHING CONTEXT
This is a culminating chapter for Part III. Earlier chapters in this section developed an
understanding of the working parts of Earth’s lithosphere and how those parts interact. This
chapter takes the various concepts learned earlier and applies them to volcanoes and
earthquakes. As in all chapters in Part III, plate tectonics informs all topics.
This chapter also emphasizes people at every opportunity. One of the reasons volcanoes
and earthquakes are inherently interesting to students is because they pose a threat. Humans
are naturally interested in threats. This chapter takes every opportunity to frame the discussion
around the lives of people. The types of threats involved, historical disasters, and safety
precautions are emphasized throughout the chapter.
TEACHING TIPS
 Tsunamis make a good opening discussion for this chapter. Students are fascinated by
tsunamis, and they directly relate to earthquakes, covered later in the chapter. Emphasize
that tsunamis are a consequence of plate tectonics.
 Students should be familiar with plate tectonics, presented in Chapter 12. Once the plate
tectonics model is understood, it is quick and easy to teach why volcanoes and earthquakes
occur and why they occur where they do.
 Emphasize the fact that volcanoes and earthquakes are geohazards for people. This is an
important distinction between geology and geography. Geography emphasizes people.
 If time is short, restrict the chapter coverage to a bare-bones minimum: Provide a
comparison between shield volcanoes and stratovolcanoes, and familiarize students with
earthquake genesis and ranking scales.
CHAPTER LEARNING GOALS
After reading the chapter and working through the study guide, students should understand
the following learning objectives for the chapter:
14.1 Describe three main types of volcanoes and major landforms associated with each.
14.2 Explain the hazards volcanoes pose and which geographic areas are most at risk.
14.3 Explain what causes earthquakes.
14.4 Describe the types of seismic waves produced by earthquakes, how earthquakes are
ranked, and what can be done to reduce our vulnerability to earthquakes.
14.5 Assess the potential links between large volcanic eruptions, Earth’s physical systems,
and people.
2
______________________________________________________________________
CHAPTER FEATURES ANSWER KEY
Crunch the Numbers
Calculating Ground Shaking and Energy Released during an Earthquake
Compared with a magnitude 2 earthquake,
1. How much more ground shaking occurs during a magnitude 5 earthquake?
Answer: 103 = 1,000 times more ground shaking.
2. How much more energy is released during a magnitude 5 earthquake?
Answer: 323 = 32,768 times more energy.
3. How much more ground shaking occurs during a magnitude 7 earthquake?
Answer: 105 = 100,000 times more ground shaking.
4. How much more energy is released during a magnitude 7 earthquake?
Answer: 325 = 33,554,432 times more energy.
Picture This: Which is the Caldera?
Consider This
1. If you found a large crater-like landform in volcanic rock, could you be 100% certain
that it is a caldera? Explain. You could not be sure that it is a caldera. Volcanic rocks
could occur near an impact crater. If shatter cone rocks are present, then it is certainly
an impact crater.
2. Note the geographic settings (see locator maps) for each landform. Based on your
reading in this chapter and in Section 12.4, is there geographic information that could
help you decide which landform is the caldera? Students may not know whether
northwestern Australia is volcanically active or not, but they should know that Hawaii is,
given the readings in the book up to this point. Therefore, it’s possible to make an
educated guess that the image on the right is the volcanic caldera.
Picture This: The Pompeii Disaster
Consider This
1. When did Mount Vesuvius last erupt? How do you think the number of people living
around the volcano then compares with the local population today? Mount Vesuvius
last erupted in 79 CE. There are millions more people today around the volcano than in
79 CE.
3
2. If given the opportunity, would you live in the red zone of Vesuvius or another risky
zone? Explain. Answers will vary. Many might say yes because it would be fun to live in
Italy and Vesuvius probably won’t erupt. This is an opportunity to get the students to
think about natural hazards and how much risk we are willing to expose ourselves to.
Picture This: Faulting Scientists
Consider This
1. Do you agree that the scientists should have been held accountable for this disaster
and prosecuted? Explain. Answers will vary. Some students will probably think the
scientists are at fault for diminishing the seriousness of the situation. Another tack
would be to say that earthquakes cannot be predicted, and we can’t hold the scientists
accountable.
2. What other natural hazards might present a similar situation and similar liability for
scientists? Hurricanes, tornadoes, tsunamis, and so on could all create liability for
scientists.
3. If scientists were held legally liable for bad predictions of natural disasters, how might
the future of their scientific fields be affected? They might be reluctant to enter the
field of hazard prediction.
Exploring with Google Earth
To complete these problems, first read the chapter. When you are finished, go to Launchpad
and open the Google Earth file for this chapter. Click on the “Workbook Problems” folder to
“fly” to each of the problems listed below and answer the questions. Be sure to keep your
“Borders and Labels” layer activated. Refer to Appendix 4 if you need help using Google Earth.
Problem 14.1
This placemark lands on Volcán de Colima in Mexico. Pan around and carefully examine the
summit crater.
1. What kind of volcano is this?
a. Stratovolcano
b. Shield volcano
c. Cinder cone
d. Plug dome
(answer: A)
2. Zoom in. What landform is visible in Colima’s summit crater?
a. A plug dome
b. A lahar
c. A cinder cone
d. A shield volcano
(answer: A)
4
Problem 14.2
This placemark highlights a volcanic landform.
1. What is the name of this volcanic landform?
a. A plug dome
b. A lahar
c. A cinder cone
d. A caldera
(answer: C)
2. Is it active?
a. Yes
b. No
(answer: B)
3. What kind of volcano can make such a landform?
a. A stratovolcano
b. A shield volcano
c. Both a stratovolcano and a shield volcano
(answer: C)
4. Zoom out. Where is this?
a. Iran
b. Turkey
c. Greece
d. Italy
(answer: B)
Problem 14.3
This placemark is on a coastal location. Note that the historical imagery feature is activated in
the upper portion of your screen. It shows an aerial photo for 07/22/2010. (If it is not activated,
be sure to activate it.)
1. Which of the following best describes the condition of the surface on 07/22/2010?
a. There is nothing unusual about the surface.
b. The surface has been slightly disturbed by some natural event.
c. The surface has been destroyed by some natural event.
(answer: A)
2. Now move the historical imagery slider to the right and stop when the date reads
03/31/2011. Wait while the aerial photo for this date loads. Which of the following best
describes the situation on the ground on this date?
a. There is nothing unusual about the surface.
b. The surface has been slightly disturbed by some natural event.
c. The surface has been destroyed by some natural event.
(answer: C)
3. Zoom out. Where is this location?
a. Russia
5
b. North Korea
c. Japan
d. China
(answer: C)
4. What natural disaster most likely occurred here, given this geographic setting, the pattern
of damage, and what you have read in this chapter?
a. A volcanic explosion
b. A tsunami
c. An earthquake
d. A fire
(answer: B)
5. Move the slider all the way to the right for the most recent photo. Has this area been
rebuilt?
a. Yes
b. No
(answer: B)
Problem 14.4
This placemark highlights a large circular lake.
1. Given the subject of this chapter, what process formed this lake?
a. A caldera formed after a magma chamber collapsed. Later, it filled with water.
b. An asteroid created this crater, which filled with water.
c. A large igneous province was eroded into a bowl, then filled with water.
d. A cinder cone crater filled with water.
(answer: A)
2. Zoom in to the island in the lake. What is the name of the island landform found inside the
lake?
a. A shield volcano
b. A stratovolcano
c. A cinder cone
d. A plug dome
(answer: C)
3. Zoom out. Where is this lake?
a. Oregon
b. Washington
c. California
d. Idaho
(answer: A)
Problem 14.5
This placemark lands on a large volcano in Mexico.
1. What is the name of this volcano? (Make sure your Borders and Labels layer is activated.)
a. Popocatépetl
6
b. Iztaccihuatl
c. Mount Tlaloc
d. La Malinche
(answer: A)
2. What kind of volcano is this?
a. Shield volcano
b. Stratovolcano
c. Cinder cone
d. Plug dome
(answer: B)
3. Can this volcano produce explosive eruptions?
a. Yes
b. No
(answer: A)
4. There is a large city to the northwest. What city is it?
a. Veracruz
b. Puebla
c. Zacatlán
d. Mexico City
(answer: D)
5. How many kilometers away is this city?
a. 70 km
b. 90 km
c. 120 km
d. 200 km
(answer: A)
Problem 14.6
This placemark lands on a volcano in Iceland. Zoom out, tilt, and pan around to get a sense of
this volcano’s shape and dimensions.
1. What kind of volcano is this?
a. Shield volcano
b. Stratovolcano
c. Cinder cone
d. Plug dome
(answer: A)
2. Is this volcano likely to produce explosive eruptions?
a. Yes
b. No
(answer: B)
Problem 14.7
Activate the ShakeMap overlay in this folder. This problem features the 2010 Haiti earthquake.
7
1. The placemark points to the epicenter. How strong was the shaking at the epicenter?
a. Weak
b. Moderate
c. Very strong
d. Violent
(answer: D)
2. What was the potential damage at the epicenter?
a. Light
b. Moderate
c. Heavy
(answer: C)
3. Find Port-au-Prince to the east. How far in kilometers was Port-au-Prince from the
epicenter?
a. 20 km
b. 27 km
c. 38 km
d. 48 km
(answer: B)
4. How strong was the shaking in Port-au-Prince?
a. Light
b. Moderate
c. Very strong
d. Extreme
(answer: C)
5. What was the potential damage level?
a. Light
b. Moderate
c. Heavy
(answer: B)
Problem 14.8
This placemark highlights a volcano that produced a VEI 6 eruption in 1991.
1. Approximately how much material did this volcano eject during that eruption?
a. 1 km3
b. 10 km3
c. 100 km3
d. 1,000 km3
(answer: B)
2. What is the name of this volcano?
a. Pinatubo
b. Hekla
c. Tambora
d. Krakatau
8
(answer: A)
3. Which of the following best describes this volcano’s activity level?
a. Active
b. Dormant
c. Extinct
(answer: A)
4. Double-click Marker 1 in this problem's folder. What is this marker highlighting?
a. Lapilli
b. A lahar
c. Liquefaction
d. Ash
(answer: B)
Problem 14.9
Activate the ShakeMap overlay in this folder if it is not already activated. This problem features
the 2011 Tōhoku earthquake in Japan.
1. What earthquake ranking scale is provided in this overlay?
a. The moment magnitude scale
b. The Richter scale
c. The Mercalli intensity scale
(answer: C)
2. The placemark points to the epicenter of the earthquake. How far was the epicenter from
Tokyo, the world's most populous city?
a. 100 km
b. 175 km
c. 375 km
d. 450 km
(answer: C)
3. What was the approximate level of ground shaking in Tokyo?
a. Strong
b. Very strong
c. Severe
d. Violent
(answer: B)
4. What kind of damage was potentially sustained in Tokyo?
a. Light
b. Moderate
c. Heavy
(answer: B)
Problem 14.10
Deactivate any open overlays. This placemark lands on Wallace Creek in California. The
placemark points to the San Andreas Fault, running mostly east-west in this view. The stream
9
runs roughly north to south on the screen. Note the change of direction of the stream where it
crosses the San Andreas Fault.
1. What kind of fault caused the stream to change direction?
a. Normal fault
b. Reverse fault
c. Strike-slip fault
(answer: C)
2. What pattern of deformation is seen in this stream?
a. Offset
b. S wave
c. Liquefaction
d. Stick-slip
(answer: A)
3. Which of the following best describes this specific fault type?
a. Right-lateral fault
b. Left-lateral fault
c. Fault block
(answer: A)
Concept Review
The Human Sphere: Deadly Ocean Waves
1. What is a tsunami? How are tsunamis generated? Why are they geohazards? Tsunamis are
large ocean waves that are mostly generated by earthquakes. They present a serious danger to
low-lying coastal populations, making them geohazards.
14.1 About Volcanoes
2. What are the three kinds of volcanoes? Which is the smallest volcano type and which is the
largest? Describe how each is built up. Stratovolcano, shield volcano, and cinder cone are the
three types of volcanoes. Shield volcanoes are the largest, and cinder cones are the smallest.
Shield volcanoes build up by accruing lava flows. Stratovolcanoes build by accruing layers of
lava and layers of ash and pyroclastic debris. Cinder cones build piles of pyroclastics that were
formed usually during a single eruption.
3. What are the three types of lava? Explain how each behaves and what causes it to behave
that way. Mafic lava has a high temperature of about 1,000°C to 1,200°C (1,800°F to 2,200°F),
has a low silica content of 50% or less, has low viscosity, and flows easily. Middle-temperature
intermediate lava is about 800°C to 1,000°C (1,500°F to 1,800°F) and has a medium viscosity.
Andesitic lava, for example, is often called blocky lava because of its blocky texture as it moves
downslope. Felsic lava has the coolest temperature, at about 650°C to 800°C (1,200°F to
1,500°F). Felsic lava has a high silica content of 70% or greater. Its resulting high viscosity
restricts its ability to flow.
10
4. Give examples of the types of materials volcanoes produce. Briefly describe each.
Volcanoes produce materials such as pyroclasts and gases. These materials and gases are blown
out of volcanoes. These materials include the smallest particles to the largest: lapilli, pumice,
blocks, and bombs.
5. What is a joint? What is columnar jointing? In which kind of lava can it be found? Joints are
cracks and weak planes in the rocks. Columnar jointing is a geometric jointing pattern.
Columnar jointing sometimes forms as basalt (mafic lava) cools.
6. What is a large igneous province? Give three examples of where they can be found. Large
igneous provinces (LIPs) are accumulations of flood basalt lava that cover extensive geographic
areas. Three examples are the Columbia Plateau in the Pacific Northwest, the Siberian Traps in
Russia, and the Deccan Traps in India.
7. What is a caldera and how does it form? Calderas are large, circular depressions that form as
a volcano’s magma chamber is emptied and collapses on itself.
14.2 Pele’s Power: Volcanic Hazards
8. What are the two types of volcanic eruptions, and what controls which type of eruption
will occur? Gentle effusive eruptions and violent explosive eruptions. Silica content and gas
content of the magma and lava types are the most important factors determining the explosive
potential of a volcano.
9. What is the VEI? The volcanic explosivity index is a system used to rank the strength of a
volcanic eruption based on the amount of material that has been ejected from the volcano.
10. What are the two most deadly products of volcanic eruptions? Explain why each is so
hazardous. Lahars and pyroclastic flows. A lahar is a thick slurry of mud, ash, water, and other
debris that flows rapidly down a volcano. It moves quickly and rapidly buries populations in its
path. Pyroclastic flows are hot clouds of gas and dust. They also move quickly and bury and
incinerate populations caught in them.
11. Can scientists predict volcanic eruptions? Explain. Scientists can sometimes predict an
eruption within weeks or months if a volcano gives warning signs. Early warning signs include
earthquake activity, movement of the crust on the volcano, and gas emissions from the vent.
12. What is the Pacific Ring of Fire? Explain the kind of volcanoes found there and why they
are deadly. The Pacific Ocean is bordered by subducting plates in most regions. As a result,
there are many active stratovolcanoes that have long histories of violent eruptions.
14.3 Tectonic Hazards: Faults and Earthquakes
13. Describe the three types of faults. What is the direction of force and the type of
movement associated with each? A normal fault is a result of tensional force (extension) as two
fault blocks move apart, resulting in one fault block slipping down in relation to the other fault
block. A reverse fault (under certain circumstances also called a thrust fault) results from
compressional force, resulting in one block moving up in relation to another block. A strike-slip
fault occurs where one block moves horizontally in relation to another block.
14. Explain how an earthquake forms using the terms stress and friction. What is elasticrebound theory in this context? What is the stick-slip process? Geologic stress tends to move
the plates of the lithosphere. Friction tends to keep the plates in place. When stress exceeds
11
friction, the plates move and an earthquake results. Elastic-rebound theory describes how the
blocks bend, break, and rebound back to their original shapes as they move in relation to one
another. The stick-slip process refers to how the blocks may become stuck again from friction,
then slip again.
15. Define and briefly explain the following terms: focus, epicenter, and seismic waves. The
focus is the region where the rocks break. It can be a single point or a fracture zone kilometers
in length. The epicenter is directly above the focus and receives the most energy from the
earthquake. Stored stress energy is suddenly released as seismic waves that shake the ground.
How much seismic energy is released during an earthquake depends on how much energy has
accumulated.
16. What is a foreshock? What is an aftershock? What causes them? Foreshocks are
earthquakes that come before a main earthquake event and are relatively small. Aftershocks
are smaller earthquakes that follow a main earthquake event. Foreshocks may be caused by
smaller cracks developing as the deformed and stressed crust is about to fail. Aftershocks occur
because the blocks are settling into their new positions after they have been moved.
17. Describe the geographic pattern of earthquakes worldwide. Where do most earthquakes
occur? Geographically most earthquakes occur along coastal regions where there is subduction,
inland where collision is occurring, and within ocean basins where seafloor spreading is active.
Most earthquakes occur on plate boundaries in seismic belts.
14.4 Unstable Crust: Seismic Waves
18. Compare a body wave to a surface wave. Where does each travel? Body waves pass
through the “body” of Earth. Surface waves travel through the surface of the crust.
19. Compare a compressional wave with a shear wave. What kind of movement does each
produce? Compressional waves produce motion that goes back and forth in a direction parallel
to the direction of the travelling waves. Shear waves move back and forth perpendicular to the
direction the waves are traveling.
20. What scientific instrumentation is used to measure ground shaking? A seismograph, or
seismometer.
21. Compare P waves, S waves, L waves, and R waves in terms of the sequence of their arrival
after an earthquake and the strength of the ground shaking they cause. P waves are fasttraveling seismic waves that are compressional and move through the body of Earth. They are
always the first to arrive. They are soon followed by S waves. S waves move perpendicularly to
the direction they travel and also move through the body of Earth. L waves and R waves arrive
last and produce the greatest shaking.
22. What does the Mercalli scale indicate about an earthquake? What evidence does it use to
rank earthquakes? The Mercalli scale ranks earthquakes based on how much damage they do
to human-built structures. The earthquake ranking varies depending on distance from the
epicenter.
23. What information about an earthquake does the moment magnitude scale provide? The
moment magnitude scale ranks earthquakes based on the amount of ground movement
produced as measured with a seismometer. This system provides a single magnitude ranking
based on the amount of energy released from the earthquake. It provides how much ground
12
shaking occurs—each whole number increase indicates 10X more ground shaking. It also
provides the amount of energy released—each whole number indicates that 32X more energy
was released.
24. What is liquefaction? On what kind of ground does it occur? Liquefaction is the
transformation of solid sediments into an unstable slurry during ground shaking in an
earthquake. Loose sediments are vulnerable to liquefaction.
25. Can scientists predict earthquakes? Scientists cannot predict earthquakes. They can
determine the probability that an earthquake will strike, but they cannot determine exactly
when any given earthquake will occur.
26. In what ways can people reduce their vulnerability to earthquakes? Retrofit old buildings,
apply rigorous standards to new buildings, and create alert systems that provide lead time to
take cover. At home, people can secure heavy items to walls, learn how to shut the gas off, and
keep a survival kit.
14.5 Geographic Perspectives: The World’s Deadliest Volcano
27. What kind of volcano is Tambora? In the context of plate tectonics, explain how Tambora
was formed. It’s a stratovolcano. It is on a volcanic island arc that was formed by subduction.
28. Given the VEI ranking of Tambora’s 1815 eruption, how much pyroclastic material did it
eject into the atmosphere? It was a VEI 7. It put over 100 cubic kilometers of material into the
atmosphere.
29. When was the “Year without a Summer,” and how does the term volcanic winter relate to
it? The Year without a Summer was in 1816. It was caused by the veiling effect of Tambora’s
ash and sulfur dioxide in the stratosphere. The term volcanic winter refers to the fact that large
volcanic eruptions that eject dust and gas into the stratosphere can cause cooling of the lower
atmosphere for one to two years following the eruption.
30. Outline the negative effects the Tambora eruption set in motion for various parts of the
world. North America, Europe, Argentina, South Africa, India, and China all experienced
unusually cold summers in 1816. There was snow in New England in every month of the year in
1816. There was crop failure in North America and Europe. There was a typhus outbreak in
Europe. The Indian monsoon caused widespread crop failure and famine resulted. Cholera
broke out in India because people were weakened by famine. This cholera spread to Europe,
China, and Russia.
Critical Thinking Questions
1. Are you vulnerable to volcanic hazards where you live? If you are unsure, how would you
find out? Answers will vary. Mostly in the United States, the Pacific Northwest is vulnerable to
volcanoes. A student could use the maps in this chapter to determine his or her vulnerability to
volcanoes.
2. Is there a risk of an earthquake occurring where you live? If you do not know, what kinds of
questions could you ask to find out? Answers will vary. Students can use the maps provided in
13
this chapter to determine their vulnerability to earthquakes. Students in the west are far more
likely to experience earthquakes than those east of the Rockies.
3. If a VEI 6 or greater eruption occurred today, what effects do you think it would have
locally (where you live) and globally? Answers will vary. Generally, students should understand
what volcanic winter is and how that affects global food supply and climate.
4. Do you think scientists will ever be able to predict accurately when a given region will be
hit by an earthquake? Answers will vary. Students might take the position that technology will
eventually enable scientists to do this. Another angle is that earthquakes will always be
impossible to predict because they occur randomly in time.
5. In Sri Lanka, many elephants ran to high ground minutes before the 2004 tsunami struck,
even though their unknowing riders ordered them to stop. Similarly, there are many
eyewitness accounts of animals such as horses and dogs acting strangely or panicking minutes
before an earthquake strikes. What do you think animals may be sensing that humans and
scientific instruments are not sensing? Do you think scientists should pursue further research
into this area, or would it be a waste of money? These animals are clearly sensing something,
but nobody knows what it is. Students may or may not think it’s a waste of money. Answers will
vary. If animals could be used to reliably predict earthquakes then the investment in research
would be worth it.
Test Yourself
Take this quiz to test your chapter knowledge.
1. True or false? Shield volcanoes produce effusive eruptions. (answer: true)
2. True or false? Lava viscosity is in large part the result of the silica content of the lava.
(answer: true)
3. True or false? Lava is one of the most deadly hazards of volcanoes. (answer: false)
4. True or false? S waves travel fastest and are the first to arrive after an earthquake. (answer:
false)
5. Multiple choice: Which of the following is not associated with explosive volcanic eruptions?
a. Stratovolcano
b. Felsic magma
c. Caldera formation
d. Large igneous province
(answer: D)
6. Multiple choice: Which of the following types of seismic waves produces a rolling movement
on the surface of Earth’s crust?
a. P waves
b. S waves
c. L waves
d. R waves
(answer: D)
14
7. Multiple choice: About how much more ground shaking does a magnitude 8 earthquake
create than a magnitude 5 earthquake?
a. 100 times more
b. 1,000 times more
c. 10,000 times more
d. 100,000 times more
(answer: B)
8. Multiple choice: Which of the following is not a type of pyroclast?
a. Bombs
b. Ash
c. Lapilli
d. Lava flows
(answer: D)
9. Fill in the blank: A __________ is a slurry of mud created when a snow-capped volcano
erupts. (answer: lahar)
10. Fill in the blank: The __________ is the point directly over an earthquake’s focus. (answer:
epicenter)
Normal or reverse fault
Strike-slip fault
Normal or reverse fault
Living Physical Geography Questions
15
1. What is a tsunami? A tsunami is a giant ocean wave triggered by a natural event, usually
an earthquake. When these waves reach shallow coastal waters, they can grow to great heights
and devastate coastal areas.
2. Why do some volcanoes explode violently? Volcanoes explode violently when gas in
magma expands rapidly as the magma migrates upward toward the crust and experiences less
pressure.
3. What causes earthquakes? When crust under stress suddenly breaks and moves, ripples
of energy travel outward and shake the ground.
4. What was the “Year without a Summer”? The year 1816 was named the “Year without a
Summer” in eastern North America because of the cooling effects of aerosols from the
Tambora eruption in the stratosphere.
16