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Chapter 7 Volcanoes and Other Igneous Activity
1) Which type of basaltic lava flow has a fairly smooth, unfragmented, ropy surface?
A) aa
B) pahoehoe
C) pumice
D) scoria
Answer: B
Diff: 1
LO/Section: 7.3
Bloom's Taxonomy: Knowledge
2) ________ lava is the most abundant type erupted at oceanic spreading centers.
A) Rhyolitic
B) Andesitic
C) Basaltic
D) Granititc
Answer: C
Diff: 1
LO/Section: 7.11
Bloom's Taxonomy: Comprehension
3) Which of the following factors help determine whether a volcanic eruption will be violent or relatively quiescent?
A) temperature
B) composition of the lava
C) amount of dissolved gases in the lava
D) all of the above
Answer: D
Diff: 1
LO/Section: 7.2
Bloom's Taxonomy: Comprehension
4) The most violent volcanic activity is associated with ________.
A) the Mid-Atlantic Ridge
B) composite volcanoes
C) cinder cones
D) shield volcanoes
Answer: B
Diff: 3
LO/Section: 7.2, 7.7
Bloom's Taxonomy: Synthesis
5) The Columbia Plateau in the northwestern United States is an excellent example of ________.
A) an eroded shield volcano
B) a caldera
C) pyroclastic flow deposits
D) flood basalts
Answer: D
Diff: 1
LO/Section: 7.9
Bloom's Taxonomy: Knowledge
6) Mauna Loa, a volcano in Hawaii, is an excellent example of a ________.
A) shield volcano
B) cinder cone
C) composite volcano
D) volcanic neck
Answer: A
Diff: 1
LO/Section: 7.5
Bloom's Taxonomy: Knowledge
Parícutin is an example of a ________.
A) shield volcano
B) cinder cone
C) composite volcano
D) volcanic neck
Answer: B
Diff: 1
LO/Section: 7.6
Bloom's Taxonomy: Knowledge
8) Three of the following statements about the May, 1980 eruption of Mount St. Helens are true. Which one is FALSE?
A) During the eruptive period, the mountain peak was substantially enlarged by new lava flows and pyroclastic debris.
B) Plumes of ash rose high into the atmosphere during the major eruptive events.
C) Mudflows called lahars accompanied the major eruptive events.
D) The most powerful explosive event was preceded by a massive landslide.
Answer: A
Diff: 2
LO/Section: 7.1, 7.8
Bloom's Taxonomy: Analysis
9) ________ tend to increase the explosive potential of a magma body beneath a volcano by the greatest amount.
A) High viscosity and lots of dissolved gas
B) High viscosity and very low levels of dissolved gas
C) Low viscosity and lots of dissolved gas
D) Low viscosity and very low levels of dissolved gas
Answer: A
Diff: 1
LO/Section: 7.2
Bloom's Taxonomy: Comprehension
10) ________ destroyed the city of St. Pierre, Martinique in 1902.
A) Lahars (volcanic mudflows)
B) A pyroclastic flow
C) Lava flows
D) Heavy ash fall
Answer: B
Diff: 1
LO/Section: 7.8
Bloom's Taxonomy: Knowledge
11) Magma tends to rise toward Earth's surface principally because ________.
A) water is an abundant constituent of magma
B) silica increases the viscosity of the magma
C) rocks become less dense when they melt
D) of convection in the mantle
Answer: C
Diff: 1
LO/Section: 7.2
Bloom's Taxonomy: Comprehension
A) shield volcano
B) cinder cone
C) composite volcano
D) volcanic neck
Answer: C
Diff: 2
LO/Section: 7.7
Bloom's Taxonomy: Analysis
What caused the many small holes that are seen in this sample of scoria?
A) impacts by volcanic bombs
B) dissolving away of minerals
C) degassing of volatiles
D) raindrops
Answer: C
Diff: 1
LO/Section: 7.3
Bloom's Taxonomy: Knowledge
14) A long-lived magma source located in the mantle is called a ________.
A) magma welt
B) plume
C) hot spot
D) basalt spout
Answer: C
Diff: 1
LO/Section: 7.12
Bloom's Taxonomy: Knowledge
15) If you want to melt a rock, even partially, there are three methods you can employ. Which of the following is NOT a way that melting is triggered in rocks in the Earth?
A) adding heat
B) releasing pressure
C) adding water
D) removing water
Answer: D
Diff: 1
LO/Section: 7.11
Bloom's Taxonomy: Comprehension
16) Which one of the following shows the correct order (from left to right) of decreasing magma viscosity? (remember that viscosity is resistance to flow, so you should pick the answer that has the most viscous lava type on the left, and the least viscous (most runny) on the right.
A) rhyolite, andesite, basalt
B) andesite, rhyolite, basalt
C) basalt, andesite, rhyolite
D) andesite, basalt, rhyolite
Answer: A
Diff: 2
LO/Section: 7.2
Bloom's Taxonomy: Analysis
17) A volcanic island arc is the result of ________.
A) subduction of continental crust underneath oceanic crust
B) subduction of oceanic crust underneath oceanic crust
C) subduction of continental crust underneath continental crust
D) subduction of oceanic crust underneath continental crust
Answer: B
Diff: 1
LO/Section: 7.12
Bloom's Taxonomy: Comprehension
18) Which of the following best describes Shiprock, a famous volcanic feature in New Mexico?
A) a very recently active, basaltic cinder cone
B) the eroded remains of a volcanic neck and radiating dikes
C) an extinct, massive, rhyolitic shield volcano
D) an extinct, highly symmetrical, composite volcanic cone
Answer: B
Diff: 1
LO/Section: 7.10
Bloom's Taxonomy: Knowledge
19) The recent volcanic activity in Yellowstone National Park is caused by ________.
A) subduction
B) a divergent plate boundary
C) intraplate volcanism
D) a transform plate boundary
Answer: C
Diff: 1
LO/Section: 7.9
Bloom's Taxonomy: Knowledge
20) How are Iceland's volcanoes related to plate tectonics?
A) They lie on an oceanic spreading center where two plates are diverging.
B) They lie on a continental rift where two plates are diverging.
C) They lie on a subduction zone where two plates are converging.
D) They lie on a continent with a hot spot below it.
Answer: A
Diff: 2
LO/Section: 7.12
Bloom's Taxonomy: Application
21) Multiple plutons can coalesce (merge) to form a(n) ________.
A) batholith
B) sill
C) neck
D) dike
Answer: A
Diff: 1
LO/Section: 7.10
Bloom's Taxonomy: Knowledge
22) Which of the following best describes the bedrock in the Sierra Nevada Mountains in California?
A) laccolith made of basalt
B) batholith made of granite
C) dike made of andesite
D) cinder cone
Answer: B
Diff: 1
LO/Section: 7.10
Bloom's Taxonomy: Knowledge
Examine the figure and consider a rock under the conditions shown by the black dot labeled "Start here." What would you have to do to that rock in order to cause it to begin melting?
A) increase its temperature
B) decrease its pressure
C) add water
D) Any of these could help the rock to melt.
Answer: D
Diff: 2
LO/Section: 7.11
Bloom's Taxonomy: Analysis
24) How do calderas form?
A) collapse of a partially emptied magma chamber
B) explosive eruption carving out a big hole in the ground
C) impact of a meteorite
D) erosion by lava flows
Answer: A
Diff: 1
LO/Section: 7.9
Bloom's Taxonomy: Knowledge
7.2 True-False
1) Lava flows are the greatest volcanic hazard.
Answer: FALSE
Diff: 2
LO/Section: 7.8
Bloom's Taxonomy: Analysis
2) Ash and lapilli are different sized pyroclastic particles.
Answer: TRUE
Diff: 1
LO/Section: 7.3
Bloom's Taxonomy: Knowledge
3) In magma, dissolved gases make up less than 10% of its weight.
Answer: TRUE
Diff: 1
LO/Section: 7.2, 7.3
Bloom's Taxonomy: Knowledge
4) The viscosity of magma increases with an increasing percentage of silica.
Answer: TRUE
Diff: 1
LO/Section: 7.2
Bloom's Taxonomy: Comprehension
5) A high viscosity means that a lava is very fluid or runny.
Answer: FALSE
Diff: 1
LO/Section: 7.2
Bloom's Taxonomy: Comprehension
6) Generally speaking, Hawaiian volcanoes are more explosive than the volcanoes of the Cascade Range.
Answer: FALSE
Diff: 2
LO/Section: 7.1, 7.12
Bloom's Taxonomy: Analysis
7) Magma generation almost always involves partial melting, not complete melting of the source rock.
Answer: TRUE
Diff: 1
LO/Section: 7.11
Bloom's Taxonomy: Comprehension
8) Hawaii is located on a plate boundary.
Answer: FALSE
Diff: 1
LO/Section: 7.12
Bloom's Taxonomy: Knowledge
9) The Andes are an example of a continental volcanic arc forming at convergent plate boundary.
Answer: TRUE
Diff: 1
LO/Section: 7.12
Bloom's Taxonomy: Knowledge
10) Repeated eruptions of relatively fluid lava from fissures can eventually cause an area to be covered by flood basalts.
Answer: TRUE
Diff: 1
LO/Section: 7.9
Bloom's Taxonomy: Comprehension
11) In general, cinder cones are much larger than shield volcanoes.
Answer: FALSE
Diff: 1
LO/Section: 7.5, 7.6
Bloom's Taxonomy: Knowledge
12) Crater Lake in Oregon actually occupies a caldera, not a crater.
Answer: TRUE
Diff: 1
LO/Section: 7.9
Bloom's Taxonomy: Knowledge
13) Water vapor is the most abundant gaseous component dissolved in most magmas.
Answer: TRUE
Diff: 1
LO/Section: 7.3
Bloom's Taxonomy: Knowledge
14) Eruption columns would be more likely to occur at a shield volcano like Kilauea than at a composite volcano like Mount St. Helens.
Answer: FALSE
Diff: 2
LO/Section: 7.2
Bloom's Taxonomy: Analysis
15) Lava tubes would be more likely to be form at a shield volcano like Kilauea than at a composite volcano like Mount St. Helens.
Answer: TRUE
Diff: 3
LO/Section: 7.1, 7.3
Bloom's Taxonomy: Synthesis
1) Gases like water vapor or carbon dioxide that get released from lava or magma are referred to as ________.
Answer: volatiles
Diff: 1
LO/Section: 7.3
Bloom's Taxonomy: Knowledge
2) ________ is type of basaltic lava flow has its surface covered with sharp-edged, angular blocks and rubble.
Answer: Aa
Diff: 1
LO/Section: 7.3
Bloom's Taxonomy: Knowledge
3) A(n) ________ is a dangerous, fast moving, hot, turbulent cloud of volcanic gases and solid particles.
Answer: pyroclastic flow (or nuée ardente)
Diff: 1
LO/Section: 7.8
Bloom's Taxonomy: Knowledge
4) A small, igneous rock body emplaced at shallow depths by uplift and arching of the overlying, older strata is a(n) ________.
Answer: laccolith
Diff: 1
LO/Section: 7.10
Bloom's Taxonomy: Knowledge
5) ________ volcanoes are closely associated with convergent plate boundaries and subduction zones.
Answer: Composite (or strato-)
Diff: 1
LO/Section: 7.7
Bloom's Taxonomy: Comprehension
6) When magma intrudes other rocks, it may ________ before reaching the surface, producing intrusions called plutons.
Answer: cool, crystallize, solidify, or congeal
Diff: 1
LO/Section: 7.10
Bloom's Taxonomy: Comprehension
7)
Shiprock, New Mexico, is a classic example of ________.
Answer: a volcanic neck
Diff: 1
LO/Section: 7.9
Bloom's Taxonomy: Comprehension
8) Shield volcanoes consist of many successive layers of ________ and lack significant amounts of pyroclastic debris.
Answer: lava
Diff: 1
LO/Section: 7.5
Bloom's Taxonomy: Knowledge
9)
What kind of volcano is pictured here?
Answer: cinder cone
Diff: 2
LO/Section: 7.6
Bloom's Taxonomy: Analysis
10) ________ are pyroclastic materials that are larger than ash, but smaller than blocks or bombs.
Answer: Lapilli
Diff: 1
LO/Section: 7.3
Bloom's Taxonomy: Knowledge
What igneous feature is shown in this photograph? ________
Answer: columnar jointing
Diff: 2
LO/Section: 7.10
Bloom's Taxonomy: Analysis
12) When mantle peridotite partially melts beneath an oceanic ridge, ________ magma is produced.
Answer: basaltic or mafic
Diff: 2
LO/Section: 7.11
Bloom's Taxonomy: Application
13) The Year Without A Summer (1816) was triggered by ________.
Answer: the eruption of Tambora in 1815, and that volcano's explosive injection of sulfate particles into the stratosphere, screening out incoming sunlight
Diff: 3
LO/Section: 7.8
Bloom's Taxonomy: Synthesis
14) The difference between lava and magma is lava is found ________ Earth's surface; whereas magma is ________ the surface.
Answer: at or near; below
Diff: 1
LO/Section: 7.3
Bloom's Taxonomy: Comprehension
15) ________ are pyroclastic materials ejected from volcanoes as liquid droplets; they cool and form a solid crust before they land.
Answer: Bombs
Diff: 1
LO/Section: 7.3
Bloom's Taxonomy: Knowledge
Copyright © 2014 Pearson Education, Inc.
Match the descriptions and locations with one of the three principle kinds of volcanoes.
A) composite/stratovolcanoes
B) shield volcanoes
C) cinder cones
1) large, fairly steep-sided cones composed of alternating layers of lava flows and pyroclastic material
Diff: 1
LO/Section: 7.7
Bloom's Taxonomy: Comprehension
2) small basaltic cones built during one, short, eruptive episode; dominated by pyroclastic material
Diff: 1
LO/Section: 7.5
Bloom's Taxonomy: Comprehension
3) volcanoes of southwestern Alaska and the Aleutian Islands
Diff: 1
LO/Section: 7.6
Bloom's Taxonomy: Comprehension
4) big volcanoes of Hawaii
Diff: 1
LO/Section: 7.6
Bloom's Taxonomy: Comprehension
5) volcano Parícutin in Mexico
Diff: 1
LO/Section: 7.6
Bloom's Taxonomy: Comprehension
1) Label each of the features of the volcano in the boxes provided.
Answer:
Diff: 1
LO/Section: 7.4
Bloom's Taxonomy: Knowledge
Answer the questions in complete sentences. Be complete but concise.
1) Imagine that you have a friend moving to a new area on the North American continent where there is a subduction zone offshore. What sorts of volcanoes would be most likely in this setting? Which volcanic hazards should you warn your friend to be alert for?
Answer: This is the setting for a continental volcanic arc. The volcanoes are most likely to be composite volcanoes, with andesitic compositions that are typically very explosive. Pyroclastic flows, ash falls, and lahars would be at the top of the risk list, though lava flows may also occur.
Diff: 3
LO/Section: All
Bloom's Taxonomy: Synthesis
Examine the map of the Cascadia subduction zone and explain why an eruption of Mount Rainier would be considerably more destructive than the similar eruption of Mount Mazama, which formed Crater Lake during a massive eruption 7,700 years ago.
Answer: Rainier is a lot closer to really big population centers lining Puget Sound, and upslope of them (i.e. lahar risk).
Diff: 2
LO/Section: 7.12, 7.8
Bloom's Taxonomy: Application
3) Volcanoes are generally not preserved in the geologic rock record as they are eroded away. However, the various materials erupted from volcanoes are often found preserved in the rock record. How could you infer what type of volcano erupted in a given area based on the type of volcanic deposits now found as layers of rock? Give specific examples and briefly discuss if some materials may be linked to different types of volcanoes.
Answer: Volcanic ash, sometimes deposited thousands of miles away from the erupting volcano, is frequently preserved in the rock record. These ash deposits accurately reflect the chemistry of the source volcano, which must be fairly explosive to produce the eruption column in the first place. Composite volcanoes are most likely to be preserved in terms of their ash deposits.
Diff: 2
LO/Section: 7.3, 7.7
Bloom's Taxonomy: Analysis
4) Discuss the six different tectonic settings in which volcanism can occur, and why magma is produced at each location.
Answer: Volcanoes can be triggered by the subduction that occurs at convergent boundaries, either (1) at an oceanic lithosphere-oceanic lithosphere subduction zone, or (2) a subduction zone where oceanic lithosphere is subducting under continental lithosphere. Magma is produced when subducted slabs give off water, which lowers the melting temperature of the neighboring/overlying mantle. Volcanoes may also occur at divergent boundaries, either at (3) continental rifts, or (4) oceanic ridges. Decompression melting of the underlying mantle is typically the cause here. Lastly, rising mantle plumes and hotspots can cause volcanism, far from any plate boundary. This intraplate volcanism may occur either beneath (5) oceanic lithosphere, e.g. Hawaii, or (6) continental lithosphere, e.g. Yellowstone. Addition of heat from Earth's deep interior and the decompression of rising warm rock (due to convection) both play a role here.
Diff: 1
LO/Section: 7.12
Bloom's Taxonomy: Comprehension
Copyright © 2014 Pearson Education, Inc.
1) You are a field geologist, dropped off in a new area. You examine the rocks of this area and find rhyolite, welded tuff, and scattered pumice. All are very young. You begin mapping the area, and soon have a rough sense of the distribution of rock units, as shown here:
Note that the welded tuff varies systematically in its thickness, and that a lake is present near the center of your mapping area. How do you interpret this pattern?
Answer: This looks like an explosive volcanic center, with a caldera in the middle, a spot where the rhyolite flows emerged. The pyroclastic flows that deposited the tuff emerged there, too, as evidenced by their thickening closer to the source. Apparently, these pyroclastic flows flowed out in all directions, but in particular to the west, as the oval shape of the tuff deposits extend furthest from the vent in that direction. Because these features appear to be relatively undisturbed, the area is potentially at risk of another eruption. Seismic and gas monitoring should be started immediately.
Diff: 3
LO/Section: 7.8, 7.9
Bloom's Taxonomy: Synthesis
Olympus Mons is an enormous volcano on Mars. It is the largest volcano in the Solar System. Compositionally and structurally, Olympus Mons is most like a shield volcano on Earth, but it is many times larger. Why should Mars produce such a monstrous shield volcano, while Earth isn't capable of producing one that large?
Answer: Earth has plate tectonics. Mars does not. Shield volcanoes erupted due to hot spot activity on Earth get carried away from their hot spot magma source due to the motion of the plate on which they are erupted. On Mars, no such lateral motion exists, and so the lava keeps piling up for the duration of the hot spot's activity.
Diff: 2
LO/Section: 7.5
Bloom's Taxonomy: Analysis
3) Pick three of the following volcanic regions and assign it to one of the three types of volcanism (convergent plate boundaries, divergent plate boundaries, or intraplate volcanism):
a. Crater Lake
b. Hawaii's Kilauea
c. Mount St. Helens
d. East African Rift
e. Yellowstone
f. Vesuvius
g. Deccan Plateau
h. Iceland
Give a brief explanation of how the volcanoes formed at each of the three locations you select.
Answer: Answers will vary, and will no doubt reflect emphasis on specific areas made by the instructor, but may look something like this:
a. Crater Lake composite volcano due to subduction of the Juan de Fuca plate beneath western North America.
b. Hawaii's Kilauea shield volcano due to hot spot under Pacific Plate
c. Mount St. Helens composite volcano due to subduction of the Juan de Fuca plate beneath western North America.
d. East African Rift divergent boundary; continental rift. Kilimanjaro is an example of an offaxis volcano due to decompression melting beneath.
e. Yellowstone caldera due to hot spot under North American Plate
f. Vesuvius composite volcano in Italy
g. Deccan Plateau flood basalts in India that erupted during the Cretaceous
h. Iceland divergent boundary (Mid-Atlantic Ridge), *coupled with a hotspot!
Diff: 2
LO/Section: 7.12
Bloom's Taxonomy: Application
Copyright © 2014 Pearson Education, Inc.