Chapter 5 Volcanoes and Other Igneous Activity
Earth: An Introduction to Physical Geology, 9e (Tarbuck/Lutgens)
5.1 Multiple-Choice Questions
1) In 1980, ________ was the first Cascade Range volcano to erupt since Mt. Lassen, California,
in 1915-16.
A) Mt. Rainier
B) Mt. Shasta
C) Kilauea
D) Mt. St. Helens
Answer: D
Diff: 1
2) Which type of basaltic lava flow has a fairly smooth, unfragmented, ropy surface?
A) aa
B) pegmatitic
C) pahoehoe
D) scoria
Answer: C
Diff: 1
3) ________ is a major dissolved volatile constituent in both magmas and volcanic gases?
A) Water
B) Carbon monoxide
C) Hydrogen chloride
D) Methane
Answer: A
Diff: 1
4) Volcanic bombs originate ________.
A) as laser-guided, granite blocks launched from a supersonic jet
B) as blocks of volcanic rock ejected from an erupting volcanic crater
C) as erupted magma blobs that partly congeal before falling to the ground
D) as ash particles that join together in the eruptive plume and fall as cobble-sized objects
Answer: C
Diff: 1
5) Which natural phenomenon occurs for many years after major explosive volcanic eruptions
such as Tambora and Pinatubo?
A) heavy falls of volcanic ash within 100 km of the volcano
B) unusually warm weather in the tropics and subtropics
C) a worldwide rise in sea level of one to three centimeters
D) brilliantly colored sunrises and sunsets
Answer: D
Diff: 1
1
6) What fate befell the 'Lost City of Atlantis' mentioned in Plato's writings?
A) It washed away in a giant sea wave about 79 A.D.
B) It was obliterated by dust storms from North Africa in the fifth century A.D.
C) It was buried by thick ash deposits from Mt. Vesuvius in 79 B.C.
D) It disappeared as part of caldera collapse following a major, explosive, volcanic
eruption.
Answer: D
Diff: 1
7) ________ magma is the most abundant type of erupted at oceanic spreading centers.
A) Basaltic
B) Granitic
C) Andesitic
D) Pegmatitic
Answer: A
Diff: 1
8) The 1991 Pinatubo eruption in the Philippines caused brilliantly colored sunrises and
sunsets to be seen for the next few years. What caused this phenomenon?
A) The eruption added large amounts of carbon dioxide to the atmosphere.
B) The eruptive cloud destroyed parts of the Earth's protective ozone layer.
C) Radioactive atoms blown into the atmosphere glowed red as they decayed.
D) Sulfur dioxide and other erupted gases formed aerosols in the stratosphere.
Answer: D
Diff: 1
9) The ________ ocean basin is rimmed by the most subduction zones.
A) Atlantic
B) Indian
C) Pacific
D) Arctic
Answer: C
Diff: 1
10) Which was the most powerful, explosive volcanic eruption of historic time?
A) Mt. Pele, Martinique, 1902
B) Vesuvius, Italy, 79 A.D.
C) Tambora, Indonesia, 1815
D) Nevado del Ruiz, Columbia, 1985
Answer: C
Diff: 1
11) Which of the following is associated with deep mantle hot spots?
A) Vesuvius and the other volcanoes of Italy
B) the volcanoes of Hawaii and the Quaternary activity in Yellowstone National Park
C) the very young cinder cones scattered across the southwestern United States
D) Mt. St. Helens and other volcanoes of the Cascade Mountains
Answer: B
Diff: 1
2
12) Why would a plume of solid silicate rock rising slowly from deep in the mantle begin
melting as it neared the base of the lithosphere?
A) The rock heats up and expands at lower pressures, causing it to liquefy.
B) Temperatures remain high as lowered pressures decrease melting temperatures.
C) The lowered pressures cause rapid heat loss accompanied by melting.
D) none of the above
Answer: B
Diff: 1
13) Which of the following best describes seamounts and islands of the deep ocean basins?
A) huge granite batholiths intruded beneath the ocean floor
B) piles of basaltic lava flows built up from the ocean floor by multiple, summit and flank
eruptions
C) andesitic pyroclastic rocks submerged when the mountains sank below sea level
D) domed gabbro intrusions and massive, submarine, rhyolitic, pyroclastic cones
Answer: B
Diff: 1
14) Pockets of magmas can be formed by the melting of deep continental crust heated by the
intrusion of other magmas. Which of the following correctly describes this process?
A) Intrusion of basaltic magma causes deep crustal rocks to melt, producing andesitic or
rhyolitic magmas.
B) Intruded rhyolite magma causes basalt magma to form by melting of granite.
C) Intrusion of diorite magma causes basalt magma to melt from peridotite.
D) All of the above correctly describe the process.
Answer: A
Diff: 2
15) Which of the following phenomena accompanied the year without a summer (1816) in parts
of North America and northern Europe?
A) ice jams on major rivers, such as the Nile and lower Mississippi during July
B) snow falls and frosts in New England during July and August
C) crop failures and vastly reduced crop yields
D) shortened periods of daylight, such as normally occur only during winter months
Answer: B
Diff: 1
16) ________ are usually the most abundant gases emitted during basaltic volcanism.
A) Chlorine and sodium
B) Neon and ammonia
C) Oxygen and nitrogen
D) Water and carbon dioxide
Answer: D
Diff: 1
3
For the following items, please choose from one of the following answers.
A. shield volcanoes
B. composite/stratovolcanoes
C. cinder cones
17) ________ massive, gently sloping volcanoes built of successive, basaltic lava flows
Answer: A
Diff: 1
18) ________ large, fairly steep-sided cones composed of lavas and pyroclastic layers
Answer: B
Diff: 1
19) ________ small basaltic cones built during one, short, eruptive episode
Answer: C
Diff: 1
20) ________ the volcanoes of southwestern Alaska and the Aleutian Islands
Answer: B
Diff: 1
21) ________ the big volcanoes of Hawaii
Answer: A
Diff: 1
22) Which statement about the May, 1980, eruption of Mount St. Helens is false?
A) During the eruptive period, the mountain peak was substantially built up by new lava
flows and pyroclastic debris.
B) Plumes of ash rose high into the atmosphere during the major eruptive events.
C) Mudflows accompanied the major eruptive events.
D) The most powerful explosive event was preceded by a massive landslide.
Answer: A
Diff: 1
23) ________ tend to increase the explosive potential of a magma body beneath a volcano.
A) High viscosity and dissolved gas
B) High viscosity; low dissolved gas content
C) Low silica content, low viscosity
D) Low viscosity; low dissolved gas content
Answer: A
Diff: 1
24) Which type of basaltic lava flow has its surface covered with sharp-edged, angular blocks
and rubble?
A) scoria
B) pahoehoe
C) pillow lava
D) aa
Answer: D
Diff: 1
4
25) Which one of the following statements concerning volcanic blocks and bombs is true?
A) blocks are broken fragments of solid rocks; bombs have smaller sizes than lapilli
B) bombs are guided to Earth by laser beams; blocks fall anywhere
C) bombs are ejected as magma lumps; blocks are ejected as solid fragments
D) bombs and blocks are both smaller than lapilli and cinders
Answer: C
Diff: 1
26) ________ destroyed the city of St. Pierre, Martinique in 1902.
A) Mudflows
B) Basaltic lava flows
C) Heavy ashfall
D) A nueé ardente
Answer: D
Diff: 1
27) Which one of the following statements concerning cinder cones is false?
A) They are small volcanoes with fairly steep sides.
B) They are built mostly or entirely during one eruptive cycle.
C) The cinders and other pyroclastic particles are consolidated into welded tuff.
D) The cinders most commonly are basaltic.
Answer: C
Diff: 1
28) The Columbia Plateau in Washington and Oregon is ________.
A) a flood basalt plateau
B) a thick stack of welded-tuff layers
C) a caldera filled with rhyolite lava flow.
D) a field of large stratovolcanoes
Answer: A
Diff: 1
29) Which kind of eruptive activity is most likely to be highly explosive?
A) Lava flows from a large shield volcano on an oceanic island.
B) Fissure eruptions feeding lava to flood basalt accumulations.
C) Eruptions of big, continental margin, composite cones or stratovolcanoes.
D) Lava flows from a large cinder cone complex.
Answer: C
Diff: 1
30) Which one of the following statements is not true?
A) Melting temperatures of silicate rocks increase with increased pressure.
B) Melting temperatures of silicate rocks are lowered by small amounts of water.
C) Basalt magmas in general have higher temperatures than rhyolite magmas.
D) When magma reaches the surface, its dissolved gas content increases.
Answer: D
Diff: 2
5
31) Which kind of volcanism is typical of mid-oceanic ridge systems?
A) explosive; composite cones
B) submarine; basaltic lava flows
C) fissure eruptions; flood basalts fields
D) explosive; rhyolitic, pyroclastic flows
Answer: B
Diff: 1
32) Kilauea and Mauna Loa are ________.
A) explosive, rhyolitic volcanoes
B) andesitic stratovolcanoes
C) basaltic shield volcanoes
D) small, basaltic cinder cones
Answer: C
Diff: 1
33) Mount St. Helens is ________.
A) a basaltic cinder cone
B) an explosive stratovolcano
C) a basaltic shield volcano
D) a small, welded tuff cone
Answer: B
Diff: 1
34) The 1943 eruption of Paricutin in Mexico was characterized by ________.
A) mudflows and explosive ash eruptions
B) welded-tuff deposition and caldera formation
C) cinder cone building and basaltic lava
D) pyroclastic eruptions and nueé ardente flows
Answer: C
Diff: 1
35) The average composition of rocks comprising a large composite cone or stratovolcano is
similar to a (an) ________ magma.
A) basaltic
B) ultramafic
C) andesitic
D) rhyolitic
Answer: C
Diff: 1
36) A ________ volcano is a very large, gently sloping mound composed mainly of basaltic lava
flows.
A) composite
B) stratospheric
C) cinder cone
D) shield
Answer: D
Diff: 1
6
37) Which of the following best describes Shiprock, a famous volcanic feature in New Mexico?
A) a very recently active, basaltic cinder cone
B) an extinct, highly symmetrical, composite volcanic cone
C) the eroded remains of a volcanic pipe and radiating dikes
D) an extinct, massive, rhyolitic shield volcano
Answer: C
Diff: 1
38) Which region has the greatest concentration of currently active volcanoes?
A) the coastal plain of western Africa
B) European Russia and Siberia
C) the area surrounding the Red Sea
D) the circum-Pacific area
Answer: D
Diff: 1
39) The recent (geologically) volcanic activity in Yellowstone National Park is ________.
A) related to plate subduction
B) related to a divergent plate boundary
C) related to a transform plate boundary
D) related to intraplate, hot spot volcanism
Answer: D
Diff: 1
40) The Icelandic volcanoes are related to plate tectonics because ________.
A) they lie on a spreading center where two plates are converging
B) they lie on a subduction zone where two plates are converging
C) they lie on a spreading center where two plates are moving apart
D) they lie along a subduction zone where two plates are diverging
Answer: C
Diff: 1
41) Which one of the following best describes volcanism in the Cascade Range, northwestern
United States?
A) related to a mantle hot spot
B) related to plate subduction
C) related to a mid-oceanic ridge system
D) related to deep, transform faults
Answer: B
Diff: 1
42) Which of the following statements best describes the big Hawaiian volcanoes?
A) lie directly above a transform plate boundary that cuts deeply into the mantle
B) lie directly above an active subduction zone where the Pacific plate is sinking into the
mantle
C) lie along the crest of the East Pacific Rise, a mid-ocean ridge or spreading center
D) are situated in the interior of a large, Pacific plate above a hot spot deep in the mantle
Answer: D
Diff: 1
7
43) At low pressures and in the absence of water, rhyolites and granites begin to melt at about
________.
A) 300°C
B) 500°F
C) 800°C
D) 6000°F
Answer: C
Diff: 1
44) What volcanic events formed Crater Lake, OR? When did they take place?
A) A powerful explosion blew away the top of a stratovolcano; 10 million years ago.
B) The crater of a large, extinct cinder cone filled with water; 5 million years ago.
C) Landslides and volcanic mudflows dammed the Mazama River; 500 years ago.
D) Caldera collapse followed major ash and pyroclastic-flow eruptions; 6000 years ago.
Answer: D
Diff: 1
45) Which one of the following shows the correct order (left to right) of decreasing magma
viscosity?
A) rhyolite, andesite, basalt
B) andesite, rhyolite, basalt
C) basalt, rhyolite, andesite
D) basalt, andesite, rhyolite
Answer: A
Diff: 1
46) Why do magmas rise toward Earth's surface?
A) Magmas are more viscous than solid rocks in the crust and upper mantle.
B) Most magmas are richer in silica than most crustal and upper mantle rocks.
C) Magmas are mainly liquid and contain dissolved fluids such as water; most are less
dense than the adjacent solid rock.
D) all of the above
Answer: C
Diff: 1
47) What is the largest, known volcano in the Solar System?
A) Mauna Loa, Hawaii, Earth
B) Mount Olympus, Greece, Earth
C) Mauna Kea, southern hemisphere, Mars
D) Olympus Mons, Mars
Answer: D
Diff: 1
8
48) A ________ is the largest, discordant body of intrusive, igneous rock.
A) lopolith
B) laccolith
C) pluton
D) batholith
Answer: D
Diff: 1
49) A ________ is an intrusive, igneous rock body that is tabular and concordant.
A) laccolith
B) dike
C) pluton
D) sill
Answer: D
Diff: 1
50) A ________ is a near surface, intrusive, igneous rock body that results from local inflation of
a horizontal sill.
A) batholith
B) dike
C) laccolith
D) volcanic neck
Answer: C
Diff: 1
51) Which of the following best describes the bedrock in the Sierra Nevada Mountains in
California?
A) basalt; dikes
B) gabbro; plutoliths
C) andesite; laccoliths
D) granite; batholiths
Answer: C
Diff: 1
52) Xenoliths are associated most closely with which magmatic process and igneous rock body?
A) columnar jointing; lava flow
B) vesiculation; pumice lump
C) magmatic differentiation; gabbro sill
D) intrusion; granitic batholith
Answer: D
Diff: 1
9
5.2 Word Analysis Questions
Examine the words and/or phrases for each question below and determine the relationship among the
majority of words/phrases. Choose the option which does not fit the pattern.
1) A) silica content
B) temperature
C) dissolved gases
D) pressure
Answer: pressure
Diff: 1
2) A) pahoehoe
B) aa
Answer: volcanic bomb
C) volcanic bomb
D) pillow lava
B) crystals
C) lapilli
D) blocks
B) pipe
C) crater
D) fumarole
B) Mt. Mazama
C) Mount Pelée
D) Kilauea
B) batholith
C) dike
D) laccolith
Diff: 1
3) A) ash
Answer: crystals
Diff: 1
4) A) caldera
Answer: caldera
Diff: 2
5) A) Mt. Vesuvius
Answer: Kilauea
Diff: 1
6) A) sill
Answer: batholith
Diff: 1
5.3 True/False Questions
1) Dissolved gases may comprise up to a few percent by weight of a magma.
Answer: TRUE
Diff: 1
2) Ash and lapilli are different sized pyroclastic particles.
Answer: TRUE
Diff: 1
3) The viscosities of magmas increase with increasing percentages of silica.
Answer: TRUE
Diff: 1
4) The eruptions of the Hawaiian volcanoes may be described as explosive in comparison to
the 1980 Mount St. Helens eruption.
Answer: FALSE
Diff: 1
10
5) Powerful, explosive, volcanic eruptions can result in climatic cooling for millions of years
following the eruption.
Answer: FALSE
Diff: 1
6) Magma generation at depth almost always involves partial melting, not complete melting of
the source rock.
Answer: TRUE
Diff: 1
7) The active Hawaiian volcanoes are situated directly above a major boundary between two of
the Earth's largest tectonic plates.
Answer: FALSE
Diff: 1
8) Most basaltic magmas are believed to form by partial melting of granite in the lower crust
and upper mantle.
Answer: FALSE
Diff: 1
9) Basaltic lavas are generally hotter and more viscous than andesite lavas.
Answer: FALSE
Diff: 1
10) Small amounts of water can lower partial melting temperatures in silicate rocks.
Answer: TRUE
Diff: 1
11) Repeated eruptions of relatively fluid lava from fissures can eventually cause an area to be
covered by flood basalts.
Answer: TRUE
Diff: 1
12) In general, cinder cones are much larger than shield volcanoes.
Answer: FALSE
Diff: 1
13) Crater Lake in Oregon actually occupies a caldera, not a crater.
Answer: TRUE
Diff: 2
14) Vents that emit only heated, volcanic gases and water are called fumaroles.
Answer: TRUE
Diff: 1
15) Aa flows are generally thinner and have smoother surfaces than pahoehoe flows.
Answer: FALSE
Diff: 1
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16) Basalt is the most common magma erupted along oceanic rift systems.
Answer: TRUE
Diff: 1
5.4 Short Answer Questions
1) Composite volcanic cones are also known as ________.
Answer: stratovolcanoes
Diff: 1
2) ________ is the most abundant gaseous component dissolved in most magmas.
Answer: H2O
Diff: 1
3) Vents that emit only hot gases and vapors are called ________.
Answer: fumaroles
Diff: 1
4) Large, volcanic depressions formed by subsidence and collapse are known as ________.
Answer: calderas
Diff: 1
5) Which basaltic lava flow has a relatively smooth surface?
Answer: pahoehoe
Diff: 1
6) What term describes fragmental volcanic material?
Answer: pyroclastic
Diff: 1
7) ________ denotes a basaltic lava flow covered with angular, congealed lava rubble.
Answer: aa
Diff: 1
8) ________ is a dangerous, fast moving, hot, turbulent cloud of volcanic gases and fine-sized,
pyroclastic particles.
Answer: nueé ardente
Diff: 1
9) A relatively small, summit depression on a volcano, marking a former eruptive vent, is a
________.
Answer: crater
Diff: 1
10) Pyroclastic fragments intermediate in size between ash and bombs are known as ________.
Answer: lapilli
Diff: 1
12
11) What kind of volcanoes are Kilauea and the other big Hawaiian volcanoes?
Answer: shield
Diff: 1
12) Another term for a volcanic mudflow is a ________.
Answer: lahar
Diff: 1
13) Which kind of volcano is closely associated with convergent plate boundaries and
subduction zones?
Answer: composite or stratovolcano
Diff: 1
14) Which tabular, discordant igneous rock body intrudes along a crack or fissure?
Answer: dike
Diff: 1
15) A very large, discordant pluton, commonly of composed of granite is a ________.
Answer: granite
Diff: 1
16) A small, igneous rock body emplaced at shallow depths by uplift and arching of the
overlying, older strata is a ________.
Answer: laccolith
Diff: 1
5.5 Critical Thinking Questions
Use complete sentences, correct spelling, and the information presented in Chapter 5 to answer the
questions below
1) Most volcanic features are readily recognized on Earth's surface today. How might you
identify ancient volcanic terrains in the rock record? Also, which features are more likely to
be preserved and identifiable after tens or hundreds of millions of years?
Diff: 3
2) Consider the differences in shape and size of shield volcanoes, cinder cones, and composite
volcanoes. How does the relative size and shape of each reflect variations in eruptive
characteristics (duration, types of materials, composition of lava, etc.)? Which eruptive
characteristics are common to all volcanoes and which ones are unique to each?
Diff: 3
3) Obviously large volumes of lava and pyroclastic debris pose serious hazards to humans.
What are some of the more indirect hazards associated with volcanic eruptions? Which of
these indirect hazards are more likely to be overlooked when planning for potential
eruptions in a given area? Why?
Diff: 3
13
5.6 Visualization Questions
1) What type of volcano is shown in the diagram below?
Answer: composite
Diff: 1
2) What type of volcano is shown in the diagram below?
Answer: shield
Diff: 1
14
3) What type of volcano is shown in the diagram below?
Answer: cinder cone
Diff: 1
4) What volcanic feature is shown in the diagram below?
Answer: lava dome
Diff: 1
15
5) On the blanks provided, write the name of the feature labeled. On the same blank, indicate
with capital letters whether the feature is concordant (C) or discordant (D) and whether the
feature is tabular (T) or massive (M).
16
6) What is the name of the chain of volcanoes above that forms at an oceanic to oceanic plate
boundary?
Answer: volcanic island arc
Diff: 1
7) What is the name of the chain of volcanoes below that forms at an oceanic to continental
plate boundary?
Answer: continental volcanic arc
Diff: 1
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