Igneous Rocks and Volcanoes

Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay
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  1. The property of a magma that determines whether or not it has high viscosity:
    1. density
    2. silica content
    3. color
    4. iron content
    5. water content
  2. Most stratovolcanoes tend to erupt:
    1. rhyolite
    2. basalt
    3. andesite
    4. gabbro
    5. obsidian
  3. This rock is so porous it often floats on water:
    1. gabbro
    2. obsidian
    3. pumice
    4. granite
    5. rhyolite
  4. After steam, the most abundant component of volcanic gases:
    1. argon
    2. carbon dioxide
    3. hydrogen sulfide
    4. sulfur dioxide
    5. nitrogen
  5. These lavas erupt coolest:
    1. pumice
    2. basalt
    3. andesite
    4. rhyolite
  6. Which of these igneous rocks is classified on the basis of its texture:
    1. dunite
    2. andesite
    3. scoria
    4. rhyolite
    5. basalt
  7. A volcano that has not erupted in 1000 years is best described as:
    1. active
    2. dormant
    3. extinct
  8. Which of these is a pyroclastic material ?:
    1. a basalt lava flow
    2. a diorite sill
    3. a batholith
    4. a volcanic mudflow
    5. volcanic ash
  9. Most batholiths are made of:
    1. granite
    2. basalt
    3. dunite
    4. gabbro
    5. rhyolite
  10. The property of a magma that determines whether or not it flows easily:
    1. density
    2. viscosity
    3. color
    4. iron content
  11. This mineral tends to form last in Bowen's Series:
    1. quartz
    2. plagioclase
    3. olivine
    4. muscovite
    5. biotite
  12. Shield volcanoes tend to erupt:
    1. rhyolite
    2. basalt
    3. andesite
    4. gabbro
    5. obsidian
  13. All these rocks have about the same chemical composition except:
    1. gabbro
    2. obsidian
    3. pumice
    4. granite
    5. rhyolite
  14. The most abundant component of volcanic gases:
    1. steam
    2. carbon dioxide
    3. hydrogen sulfide
    4. sulfur dioxide
    5. nitrogen
  15. These lavas erupt hottest:
    1. pumice
    2. basalt
    3. andesite
    4. rhyolite
  16. During its lifetime, a volcano may:
    1. collapse to form a caldera
    2. collapse in a catastrophic landslide
    3. erode away to leave a volcanic neck
    4. any of the above
  17. A volcano that has not erupted in 1000 years is extinct. True or False:
    1. True
    2. False
  18. Source of the water that forms volcanic mudflows:
    1. melting of the volcano's snow or ice cap
    2. condensation of water vapor from the eruption cloud
    3. both a and b
    4. neither a nor b
  19. The least dangerous hazard to human life from volcanoes:
    1. lava flows
    2. nuees ardentes
    3. mudflows
  20. Mount St. Helens, prior to its eruption in 1980 was an excellent example of:
    1. a shield volcano
    2. a dormant volcano
    3. an extinct volcano
    4. an active volcano
    5. none of these
  21. The steepness of slopes on a volcanic mountain is determined primarily by:
    1. the relative amounts of pyroclastic debris and lava erupted from the volcanic vent
    2. the initial temperature of the lava
    3. the amount of rainfall in the area
    4. the force with which the magma is pushed upward
    5. none of these
  22. A fiery cloud of hot gases and pyroclastic debris which flows down the side of a volcano is called:
    1. a cinder avalanche
    2. a nuee ardente or pyroclastic flow
    3. clastic flow
    4. theromoclastic avalanche
    5. none of these
  23. The steep-walled structure formed by the collapse of the top of a volcanic mountain into an underlying magma chamber is called:
    1. a crater
    2. a fissure
    3. a caldera
    4. a vent
    5. none of these
  24. The Columbia Plateau in the northwestern U.S. is an excellent example of:
    1. an eroded shield volcano
    2. deposits of flood basalts
    3. extensive deposits of pyroclastic debris
    4. a chain of composite volcanoes
    5. none of these
  25. The type of rock which is not a common volcanic rock is:
    1. andesite
    2. basalt
    3. gabbro
    4. rhyolite
    5. none of these
  26. Two types of gases, other than steam, that are most abundant in volcanic emissions are:
    1. carbon dioxide and sulfur dioxide
    2. carbon dioxide and nitrogen
    3. hydrogen and helium
    4. none of these
    5. carbon monoxide and argon
  27. Gabbro is coarser grained than basalt because:
    1. it contains more silica
    2. the original magma cooled under low pressure, so that larger crystals could form
    3. the original magma cooled more slowly
    4. the crystals have grown larger during later metamorphism
    5. none of these
  28. Granites and rhyolites are related by:
    1. their grain size
    2. their mode of emplacement
    3. their association in the ocean basins
    4. their mineralogical composition
    5. none of these
  29. Which of these processes can destroy a stratovolcano:
    1. landslide
    2. gradual erosion
    3. caldera collapse
    4. all of the above
  30. Why some minerals, like olivine and quartz, can't occur together
    1. some occur in volcanic rocks, others in plutonic rocks
    2. they are both silicates
    3. neither of them contains silica
    4. they are chemically incompatible
  31. The first question a geologist asks in classifying an igneous rock
    1. What feldspars are present?
    2. Is quartz present?
    3. What dark minerals are present?
  32. When molten rock reaches the surface, it's called:
    1. lava
    2. slag
    3. magma
    4. granite
  33. Molten rock which does not reach the surface is called:
    1. volcanic ash
    2. magma
    3. basalt
    4. lava
  34. Magma forms
    1. in the core of the earth
    2. 1000 miles below the surface
    3. a mile below the surface
    4. about 50 miles below the surface
  35. How to tell a dike from a sill
    1. a dike cuts across structures but a sill is parallel to them
    2. dikes are mostly of gabbro, sills are diorite
    3. sills are usually associated with batholiths
    4. all of the above
  36. Silica-rich lavas
    1. are usually cooler than silica-poor lavas
    2. are more viscous
    3. tend to be accompanied by more explosive eruptions
    4. all of the above
    5. none of the above
  37. An igneous rock with large crystals in a fine-grained matrix.
    1. basalt
    2. pumice
    3. scoria
    4. porphyry
  38. According to Bowen's Series:
    1. quartz forms last
    2. quartz and olivine form together
    3. quartz forms before biotite
    4. quartz forms first
  39. Obsidian
    1. is volcanic glass
    2. is usually rhyolitic in composition
    3. has conchoidal fracture
    4. all of the above
  40. A felsic magma:
    1. contains a high percentage of iron and magnesium
    2. cools to form volcanic rocks such as basalt
    3. contains more than 65% silica
    4. is characterized as silica poor
    5. contains mostly sodium and potassium
  41. The viscosity of magma is primarily controlled by:
    1. temperature
    2. texture
    3. silica content
    4. elevation
    5. pressure
  42. The most commonly emitted volcanic gas is:
    1. carbon dioxide
    2. chlorine
    3. hydrogen sulfide
    4. water vapor
    5. nitrogen
  43. An example of a concordant pluton having a tabular geometry is a:
    1. sill
    2. lava flow
    3. batholith
    4. dike
    5. volcanic neck
  44. Most pegmatites are essentially:
    1. light-colored gabbro
    2. thick accumulations of pyroclastic materials
    3. very coarse-grained granite
    4. rhyolite porphyry
    5. cylindrical plutons
  45. An igneous rock possessing a combination of mineral grains with markedly different sizes is:
    1. a natural glass
    2. the product of very rapid cooling
    3. formed by explosive volcanism
    4. a porphyry
    5. a tuff
  46. Basalt plateaus form as a result of:
    1. repeated eruptions of cinder cones
    2. widespread ash falls
    3. accumulation of thick layers of pyroclastic materials
    4. the origin of lahars on composite volcanoes
    5. eruptions of fluid lava from long fissures
  47. One other Cascade Range volcano besides Mount St. Helens has erupted since 1900. It is:
    1. Mount Hood, Oregon
    2. Mount Adams, Washington
    3. Mount Lassen, California
    4. Mount Mazama, Oregon
    5. Mount Garibaldi, British Columbia
  48. Volcanic or extrusive igneous rocks form by the cooling and crystallization of lava flows and the
    1. crystallization of magma beneath the surface
    2. consolidation of pyroclastic materials
    3. reaction of volcanic gases with the atmosphere
    4. heating of sedimentary rocks beneath lava flows
    5. all of these
  49. Which is associated with basaltic magma:
    1. shield volcanoes
    2. explosive eruptions
    3. nuees ardentes
    4. batholiths
  50. Small, steep-sided cones that form on the surfaces of lava flows where gases escape are:
    1. lava tubes
    2. pahoehoe
    3. spatter cones
    4. volcanic bombs
    5. columnar joints
  51. Much of the upper part of the oceanic crust is composed of interconnected bulbous masses of igneous rock called:
    1. pillow lava
    2. parasitic cones
    3. lapilli
    4. blocks
    5. pyroclastic material
  52. Shield volcanoes have low slopes because they are composed of:
    1. mostly pyroclastic layers
    2. felsic magma
    3. lahars and viscous lava flows
    4. pillow lavas
    5. fluid mafic lava flows
  53. Which is most dangerous to humans:
    1. nuee ardente or pyroclastic flow
    2. pahoehoe
    3. lava flows
    4. pillow lava
    5. volcanic bombs
  54. A lava flow with a surface of jagged blocks is termed:
    1. lapilli
    2. obsidian
    3. vesicular
    4. pyroclastic sheet deposit
    5. aa
  55. Most calderas form by:
    1. summit collapse
    2. forceful injection
    3. explosions
    4. erosion of lava domes
    5. fissure eruptions
  56. An igneous rock possessing mineral grains large enough to be seen without magnification is said to have a _____ texture
    1. porphyritic
    2. phaneritic
    3. aphanitic
    4. vesicular
    5. fragmental
  57. What are the two major kinds of igneous rocks:
    1. volcanic and eruptive
    2. volcanic and plutonic
    3. granitic and plutonic
    4. sills and lava
    5. dikes and batholiths
  58. Crater Lake in Oregon is an excellent example of a:
    1. caldera
    2. basalt plateau
    3. cinder cone
    4. lava dome
    5. shield volcano
  59. The volcanic conduit of a lava dome is most commonly plugged by:
    1. mafic magma
    2. volcanic mudflows
    3. columnar joints
    4. spatter cones
    5. viscous, felsic magma
  60. The largest volcano in the world (height, volume, or diameter) is:
    1. Mount St. Helens, Washington
    2. Mount Vesuvius, Italy
    3. Mount Etna, Sicily
    4. Mauna Loa, Hawaii
    5. Fujiyama, Japan
  61. The only area where fissure eruptions are currently occurring is:
    1. the Red Sea
    2. Iceland
    3. western South America
    4. Japan
    5. the Pacific Northwest
  62. Why is silica the major component of magma:
    1. it melts at low temperatures
    2. it retains heat well
    3. it dissolves other rocks
    4. it is so abundant
  63. Which of the following pairs of igneous rocks have the same mineral composition?
    1. granite-tuff
    2. basalt-gabbro
    3. andesite-rhyolite
    4. peridotite-andesite
    5. pumice-diorite
  64. Which of the following is a concordant pluton:
    1. sill
    2. dike
    3. stock
    4. batholith
    5. volcanic neck
  65. Batholiths are composed mostly of what type of rock:
    1. granitic
    2. andesite
    3. gabbro
    4. periodotite
    5. basalt
  66. Most active volcanoes are in:
    1. the Mediterranean belt
    2. the circum-Pacific belt
    3. the Hawaiian Islands
    4. the oceanic ridge belt
    5. Iceland
  67. The magma generated beneath spreading ridges is mostly:
    1. mafic
    2. intermediate
    3. felsic
    4. answers (a) and (b) only
    5. all of these
  68. The volcanoes of _____ are unrelated to either a divergent or a convergent plate margin.
    1. East Africa
    2. the Hawaiian Islands
    3. the mid-oceanic ridges
    4. Iceland
    5. the Cascade Range
  69. Volcanic rocks can usually be distinguished from plutonic rocks by:
    1. color
    2. the size of their mineral grains
    3. composition
    4. specific gravity
    5. iron-magnesium content
  70. One of history's best-known volcanic eruptions was the eruption that destroyed Pompeii in 79 A.D. How was Pompeii destroyed:
    1. It was buried by lava flows.
    2. It was buried by mudflows.
    3. It was swept away by a volcanic sea wave.
    4. It was buried by ash, which later hardened into rock.
  71. Vesuvius is one of a chain of volcanoes along the southern coast of Italy, marking a:
    1. mid-ocean ridge.
    2. subduction zone.
    3. flood basalt province.
    4. rift valley.
  72. For every lava flow that erupts from a volcano, what quantity of molten rock hardens beneath the surface:
    1. only a few per cent
    2. about the same
    3. two or three times as much
    4. many times as much
  73. When mantle material melts, it usually forms magma of what composition:
    1. basalt
    2. rhyolite
    3. andesite
    4. dunite
  74. Volcanoes on oceanic crust erupt mostly magma of what composition:
    1. basalt
    2. rhyolite
    3. andesite
    4. dunite
  75. What type of volcanism is most rarely associated with rifting of continents:
    1. basalt
    2. rhyolite
    3. andesite
  76. Subduction zones on the continents display the widest variety of igneous activity. As a rule the earliest volcanic products tend to be:
    1. rhyolite
    2. basalt
    3. andesite
    4. basalt and rhyolite
  77. As subduction zones on continents evolve, later magmas become progressively ______.
    1. richer in iron.
    2. poorer in silica.
    3. richer in magnesium.
    4. richer in silica.
  78. The largest intrusions in area and volume are:
    1. stocks.
    2. batholiths.
    3. laccoliths.
    4. lopoliths.
  79. The islands of Hawaii are:
    1. shield volcanoes
    2. stratovolcanoes
    3. plug domes
    4. fissure flows
  80. Which of the following is not an important flood basalt area:
    1. Oregon and Washington
    2. large areas in India
    3. parts of Siberia
    4. central Australia
  81. Flood basalts are usually related to:
    1. subduction zones.
    2. hot spots or rifts.
    3. batholiths.
    4. mountain ranges
  82. The most commonest intermediate volcanic rock is:
    1. andesite.
    2. basalt
    3. rhyolite
    4. diorite
  83. Stratovolcanoes are composed of :
    1. rhyolite flows.
    2. alternating layers of lava, mudflow deposits, and pyroclastic debris.
    3. mudflows and volcanic ash.
    4. loose pyroclastic debris.
  84. Why is lava, in itself, a comparatively minor safety hazard:
    1. Lava flows usually move slowly, and there is usually enough advance warning to permit escape.
    2. Lava hardens as it moves.
    3. both a. and b
    4. none of the above
  85. Most andesite stratovolcanoes occur at:
    1. continental rifts
    2. hot spots.
    3. subduction zones.
    4. oceanic rifts.
  86. Shield volcanoes are the largest of all volcanoes by what measures:
    1. height
    2. volume
    3. mass
    4. diameter
    5. all of the above
  87. The property of magma that governs the type of volcano built and the violence of its eruptions is:
    1. density
    2. temperature
    3. depth of origin
    4. viscosity
  88. Which of the following materials has the highest viscosity?
    1. hot asphalt
    2. honey
    3. milk
    4. water
  89. Which of the following magmas has the highest viscosity?
    1. rhyolite
    2. basalt
    3. andesite
    4. diorite
  90. Which of the following magmas is most likely to build a shield volcano?
    1. rhyolite
    2. basalt
    3. andesite
    4. diorite
  91. Which is the least likely to cause casualties during a volcanic eruption?
    1. mudflows
    2. pyroclastic flows
    3. fast-moving lava flows that arrive without warning
    4. building collapse from ash falls
  92. Volcanic ash is:
    1. rock dust ejected by the volcano.
    2. remains of materials burned by hot lava.
    3. minerals that condense from volcanic gases.
    4. loose soil picked up by the wind after eruptions.
  93. Which of the following magmas is most likely to be associated with violent eruptions?
    1. rhyolite
    2. basalt
    3. andesite
    4. diorite
  94. The process by which intrusions "nibble" their way upward by breaking off pieces of overlying rock is called:
    1. stoping.
    2. forceful injection.
    3. injection fracturing
    4. undermining.
  95. Which of the following magmas has the lowest viscosity?
    1. rhyolite
    2. basalt
    3. andesite
    4. diorite
  96. Which of the following magmas is most likely to be associated with a pyroclastic flow?
    1. rhyolite
    2. basalt
    3. andesite
    4. diorite
  97. All the following properties of volcanoes and eruptions tend to be associated, except one. The property that does not belong in this list is:
    1. non-violent eruptions.
    2. pyroclastic flows.
    3. shield volcanoes.
    4. fluid lavas with low viscosity.
  98. On the atomic scale, the property that governs magma viscosity, type of volcano formed, and eruptive violence is:
    1. average size of ions.
    2. average charge of ions.
    3. linkage of silica tetrahedra.
    4. ratio of large and small ions.
  99. Mount Vesuvius, Mount Fuji, Mount Rainier, and most of the other well-known volcanoes of the world are :
    1. cinder cones.
    2. shield volcanoes.
    3. stratovolcanoes.
    4. flood basalts.
  100. Sometimes, rhyolite lava emerges from a new vent and oozes out to form a:
    1. fissure eruption.
    2. plug dome
    3. cinder cone
    4. pyroclastic flow
  101. Before the advent of rapid communication and transportation for relief efforts, probably the greatest danger from volcanoes was:
    1. lava flows that struck without warning.
    2. weather disturbances caused by distant eruptions
    3. inability to evacuate people in danger
    4. starvation due to environmental disruption
  102. Most of the gas erupted by a volcano is ordinary steam, and most of the remainder is
    1. hydrogen chloride
    2. hydrogen sulfide
    3. carbon dioxide.
    4. radon
  103. The worst volcanic gas disaster known occurred in the African nation of Cameroon in 1986 It was:
    1. an outburst of carbon dioxide that suffocated many people.
    2. a sudden, explosive release of hot gases.
    3. emission of highly toxic hydrogen sulfide.
    4. emission of toxic gases that poisoned crops.
  104. The vents of many older volcanoes become so plugged with hardened lava that the vent may be permanently relocated and a new cone built on the flanks of the old one. Such a cone is called:
    1. a cinder cone
    2. a flank cone
    3. a parasitic cone.
    4. a plug dome
  105. If the magma pressure drops beneath a volcano, the volcano may subside to form a basin called a:
    1. rift valley.
    2. deflation basin.
    3. crater.
    4. caldera.
  106. A caldera is different from a volcanic crater in what way:
    1. A crater is usually much larger than a caldera.
    2. A caldera forms by explosion but a crater forms by subsidence.
    3. A caldera forms by subsidence but a crater forms by explosion.
    4. A caldera forms by erosion but a crater forms by explosion.
  107. Crater Lake in Oregon actually fills a:
    1. rift basin
    2. caldera
    3. sinkhole
    4. deflation basin.
  108. When volcanoes collapse in the sea, the results are often especially violent. Two of the most violent such eruptions were:
    1. Krakatoa and Thera.
    2. Vesuvius and Etna.
    3. Krakatoa and Mauna Loa.
    4. Surtsey and Paricutin.
  109. A former volcano in Oregon, Mount Mazama, is now the site of:
    1. Mount Hood
    2. Mount St. Helens
    3. Mount Shasta
    4. Crater Lake
  110. Yellowstone National Park is an example of:
    1. a hot spot on a continent.
    2. a collapsed magma chamber.
    3. a flood basalt province.
    4. both a. and b.
    5. all of the above
  111. Stratovolcanoes collapse because:
    1. they are weakly-cemented piles of lava flows, ash layers and mudflow deposits.
    2. acidic gases and solutions weaken the volcano from within.
    3. they accumulate glaciers whose weight collapses the volcano
    4. They trigger earthquakes that cause them to collapse
    5. both a. and b.
  112. Very large batholiths like the Sierra Nevada Batholith are:
    1. made up of dozens or even hundreds of smaller intrusions.
    2. mostly of gabbro.
    3. only a kilometer of so thick.
    4. uniform masses of rock that formed from a single vast magma body.
  113. The best-documented global cooling by a volcanic eruption occurred after the eruption of:
    1. Vesuvius in 79 A. D.
    2. Krakatoa in 1883.
    3. the Indonesian volcano Tambora in 1815.
    4. Mount Katmai in 1912.
  114. Flood basalts might have very significant global effects because:
    1. they release so much heat.
    2. they cover vast areas with dark rocks, trapping solar heat.
    3. they melt polar glaciers.
    4. the sulfur content of basaltic lava is about ten times that of rhyolite.
  115. Volcanic aerosols are made up of:
    1. fine rock powder
    2. tiny droplets of sulfuric acid
    3. tiny droplets of water vapor
    4. microscopic ice crystals.
  116. Mount Pelee caused great loss of life during its 1902 eruption because of a:
    1. pyroclastic flow.
    2. lava flow.
    3. mudflow
    4. heavy ash fall that collapsed buildings.
  117. Nevado Ruiz erupted in 1985 and killed 20,000 people because of:
    1. pyroclastic flow.
    2. lava flow.
    3. mudflow
    4. heavy ash fall that collapsed buildings.

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