Earth: An Introduction to Physical Geology, 11e (Tarbuck)
Chapter 5 Volcanoes and Volcanic Hazards
5.1 Multiple-Choice Questions
1) Using the choices below, select the statement that best explains how dissolved gases drive
volcanic eruptions.
A) As the magma rises, gas bubbles contract, fragmenting the material and expelling it from the
vent.
B) As the magma rises, gases reduce silicate mineral chains by breaking silicon-oxygen bonds,
resulting in an explosion.
C) Confining pressure decreases on a rising magma, allowing gas bubbles to expand and fracture
the magma. This further decreases pressure on the magma and will result in an explosive event.
D) Decreases in confining pressure result in decreasing viscosity of the magma, allowing the
magma to ooze from the volcano.
2) Define magma.
A) Dissolved gases in molten rock
B) A material’s resistance to flowing
C) Molten rock that has been erupted
D) Molten rock that contains dissolved gases and some crystals
3) ________ is a material’s resistance to flowing.
A) Viscosity
B) Volatiles
C) Composition
D) Quiescent
4) Which of the following lavas make up 90% of the total volume of lava on Earth?
A) Basaltic
B) Andesitic
C) Rhyolitic
5) ________ is pulverized rock, lava fragments, and ash erupted from a volcano.
A) Pahoehoe
B) Pyroclastic materials
C) Basalt
D) Lapilli
6) What is the name of the small holes created by gas bubbles on the surface of scoria?
A) Lapilli
B) Pumice
C) Vesicles
D) Volatiles
7) Around which volcano would a scientist likely find pillow basalts?
A) Mt. St. Helens
B) Parícutin
C) Fujiyama
D) Kilauea
8) Which type of magma(s) will produce scoria?
A) Basaltic
B) Andesitic
C) Rhyolitic
D) Both A and B
E) Both B and C
9) A ________ is a cone-shaped structure created by successive eruptions of volcanic materials
such as lava or pyroclastic materials.
A) Caldera
B) Volcanic cone
C) Crater
D) Fumarole
10) Which of the following choices best explains the difference between a crater and a caldera?
A) A crater is a very large circular depression over 1 km across; A caldera is a small funnel-
shaped depression.
B) A crater is a small, funnel-shaped depression; A caldera is a large depression that has a
diameter of over 1 km.
C) A crater is a fissure in the crust; A caldera is a collapsed summit.
D) A crater is a large circular depression over 1 km across; A caldera is a small, parasitic cone
growing on the flank of the volcano.
11) What interpretations can be made about the maturity of a volcano where most eruptions
occur from basal fissures and there are a number of parasitic cones along the volcano’s flanks?
A) Mature volcano
B) Early stages of growth
12) With the exception of volcanoes associated with a subduction zone, most volcanic islands are
________ volcanoes.
A) Cinder Cone
B) Shield
C) Composite Cone
D) Caldera
13) In order to cover such large expanses of seafloor, shield volcanoes erupt ________ lava.
A) Rhyolitic
B) Andesitic
C) Porphyritic
D) Basaltic
14) A ________ is a submarine volcano.
A) Seamount
B) Caldera
C) Scoria Cone
D) Dome
15) Which volcanoes have flanks with the steepest angle of repose (between 30° and 40°)?
A) Shield Volcanoes
B) Cinder Cones
C) Composite Cones
D) Lava Domes
16) Based on the structure of the cone and the rock making it up, what interpretations can be
made about the gas content of eruptions from cinder cone volcanoes compared to those of shield
volcanoes?
A) Less gas than shield volcanoes
B) Same gas content as shield volcanoes
C) More gas than shield volcanoes
D) Gas is not found in volcanoes
17) In what year did Parícutin form in a Mexican cornfield?
A) 1935
B) 1940
C) 1943
D) 1952
18) Lavas erupting from composite cones are generally ________-rich, making them very
viscous.
A) Magnesium
B) Iron
C) Aluminum
D) Silica
19) The Ring of Fire is a narrow zone of composite cone volcanoes rimming the ________
Ocean.
A) Pacific
B) Atlantic
C) Indian
D) Arctic
20) What kind(s) of lava are most closely associated with composite cones?
A) Andesite
B) Rhyolite
C) Basalt
D) Andesite and Basalt
21) What kind(s) of lava can a composite cone generate?
A) Andesite
B) Andesite and Rhyolite
C) Basalt
D) Basalt and Andesite
E) Andesite, Basalt, and Rhyolite
22) What is the driving force behind pyroclastic flows?
A) Directed explosion
B) Gravity
C) Water
D) Earthquakes
23) What kind of volcano is most closely associated with pyroclastic flows?
A) Shield
B) Cinder Cone
C) Composite Cone
D) Caldera
24) Which of the following is not a method of caldera formation?
A) Collapse of magma chamber after large volumes of material are erupted
B) Collapse of a composite cone summit following an explosive eruption
C) Collapse of summit of a cinder cone volcano after an effusive lava flow
D) Collapse of summit of a shield volcano after draining of magma chamber
25) What kind of viscosity would flood basalts have?
A) Low viscosity
B) Medium viscosity
C) High viscosity
26) An example of a volcanic caldera that formed from the collapse of a magma chamber after
large volumes of material were erupted is ________.
A) Mt. Mazama
B) Yellowstone
C) Kilauea
D) Mt. Vesuvius
27) What kind of volcanic hazard can be triggered by the collapse of a lava dome?
A) Pyroclastic flow
B) Lava flow
C) Ash fall
D) Lahar
28) Along which tectonic boundary will chains of composite cone volcanoes be located?
A) Convergent boundary
B) Divergent boundary
C) Transform boundary
D) Mantle plumes
29) What type of lava is produced at a divergent plate boundary?
A) Rhyolitic
B) Andesitic
C) Basaltic
30) How is magma generated along convergent plate boundaries?
A) Decompression melting of the mantle
B) Fluids are boiled out of the subducting plate, which lower the melting point of the
surrounding mantle
C) Friction from colliding plates melts the mantle
D) Radioactive decay melts mantle material
31) Which of the following changes are not evidence of migrating magma?
A) Changes in the pattern of earthquakes produced by moving magma
B) Magma draining from the summit of a volcanic cone
C) Increase in ground temperature
D) Changes in the volcanic gases released from the volcano
32) GPS units, satellites, and lasers are some of the tools used to monitor ________ of the
volcanic flanks, which indicates magma accumulating in the magma chamber.
A) Gas content
B) Subsidence
C) Inflation
D) Seismicity
5.2 True/False Questions
1) The more silica in magma, the lower the viscosity.
2) Pyroclastic materials are generally associated with viscous magmas.
3) Scoria has so many vesicles it will float on water.
4) Fumaroles are vents that emit volcanic gases.
5) Shield volcanoes will have no pyroclastic materials associated with their eruptions.
6) Most cinder cones have eruptive phases that last for centuries.
7) Ash can sometimes be associated with eruptions from cinder cone volcanoes.
8) Composite cones are also known as stratovolcanoes.
9) Secondary vents on composite cones can generate cinder cones.
10) Lava domes can only collapse during eruptions.
11) Kilauea is a volcano created by intraplate volcanism.
5.3 Short Answer Questions
1) Explain what will happen to the rocks of the volcano as magma moves into the magma
chamber.
2) Differentiate the three types of magma based on their igneous compositions, temperatures, and
silica contents.
3) Explain the role water dissolved in magma would play in reducing the viscosity of the magma.
4) Kilauea, a volcano in Hawaii, generates fluid, extensive lava flows. Mt. St. Helens, a volcano
in Washington State, can produce lava flows that are short and thick, but can also erupt violently
and generate large volumes of ash. Evaluate the silica content and temperature of each volcano’s
lava.
5) Assume you live near Mt. St. Helens and the volcano is going through an explosive eruption.
Explain the effect pyroclastic materials would have on your home.
6) Pahoehoe and Aa can form in the same lava flow as it flows away from the eruptive vent.
Compare and contrast pahoehoe and aa flows, taking care to comment on viscosity and
temperature of each one in your discussion.
7) Why are block lavas likely to create short, prominent flows rather than long, fluid flows?
8) Explain why volcanic bombs take on a streamlined shape.
9) What substances are emitted from fumaroles? Name three specific substances.
10) Explain how lava tubes form in basaltic lavas.
11) Explain why magma rising through the conduit of a cinder cone volcano will often break
through the side of the volcano and flow down the flank.