Quiz prepared by Leslie J. Sonder, Dartmouth College.
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1 | |
Three settings where volcanic rocks generally form are ________________. |
| | A) | subduction zones, continent-continent collision zones, mid-ocean rift systems |
| | B) | subduction zones, continent-continent collision zones, hot spots |
| | C) | subduction zones, continent-continent collision zones, continental strike-slip faults zones |
| | D) | subduction zones, hot spots, mid-ocean rift systems |
| | E) | subduction zones, continental strike-slip fault zones, mid-ocean rift systems |
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2 | |
Over 90 percent of volcanic activity is associated with ______________. |
| | A) | subduction zones |
| | B) | transform boundaries |
| | C) | hot spots |
| | D) | continent-continent collision zones |
| | E) | plate-tectonic boundaries |
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3 | |
Why is volcanism in subduction zones more explosive than in other volcanic settings? |
| | A) | Magmas in subduction zones are generally rich in silica. |
| | B) | Magmas in subduction zones contain more water because of melting of hydrated rocks and minerals. |
| | C) | Magmas in subduction zones are generally more viscous. |
| | D) | Magmas in subduction zones tend to become solid at lower temperatures thus increasing their viscosity. |
| | E) | all of the above |
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4 | |
The occurrence of geysers in Yellowstone National Park is evidence for the presence of what material below the surface? |
| | A) | melted rock |
| | B) | radioactive materials |
| | C) | diamonds |
| | D) | the asthenosphere |
| | E) | carbon dioxide |
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5 | |
Water at depths within a geyser system exists at temperatures above the boiling point at the Earth's surface. Why does the water become steam at more shallow depth and erupt? |
| | A) | Increase in pressure near the surface. |
| | B) | Increase in heat near the surface. |
| | C) | Decrease in pressure near the surface. |
| | D) | Decrease in heat near the surface. |
| | E) | Increase in radioactive decay near the surface. |
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6 | |
What are the most important factors controlling the creation (not composition) of magma? |
| | A) | radiation, water content, and oxygen |
| | B) | water content, heat, and oxygen |
| | C) | radiation, pressure, and water content |
| | D) | pressure, heat, and water content |
| | E) | heat, water content, and silicon |
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7 | |
Eruption of magma at mid-ocean ridge systems occurs mostly by ___________________. |
| | A) | decompressive melting of the lithosphere |
| | B) | decompressive melting of the asthenosphere |
| | C) | decompressive melting of core |
| | D) | decompressive melting of lower mantle |
| | E) | decompressive melting of upper crust |
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8 | |
Hot spots under the continental lithosphere generally create __________ while those under oceanic lithosphere commonly create __________. |
| | A) | calderas, shield volcanoes |
| | B) | shield volcanoes, stratovolcanoes |
| | C) | cinder cones, stratovolcanoes |
| | D) | calderas, stratovolcanoes |
| | E) | cinder cones, shield volcanoes |
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9 | |
The production of magma is favored by an increase in ____________ and __________, and a decrease in __________. |
| | A) | pressure, water content, heat |
| | B) | pressure, heat, water content |
| | C) | heat, water content, pressure |
| | D) | solar heat, water content, pressure |
| | E) | solar heat, pressure, water content |
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10 | |
The main process that causes volcanoes to explode violently is _______________. |
| | A) | hot convection currents in the asthenosphere that push magma upward |
| | B) | density differences within the magma that force part of the magma upward |
| | C) | a decrease in pressure triggering rapid expansion of the gases in a magma |
| | D) | chemically volatile substances that explode within the volcano vents |
| | E) | rapid expansion of the solid crystals in a magma with decrease in pressure |
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11 | |
Which of the following factors helps determine whether a volcanic eruption will be violent or relatively peaceful? |
| | A) | The ease with which dissolved gas escapes from the magma. |
| | B) | Temperature of magma. |
| | C) | Composition of the magma. |
| | D) | all of the above |
| | E) | Only the amount of dissolved gas in the magma and temperature of the magma. |
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12 | |
Rhyolitic magmas rich in K, Al, Na, and SiO2 typically are produced by the melting of _____________ and are associated with _____________ eruptions. |
| | A) | continental crust, highly explosive |
| | B) | continental crust, peaceful |
| | C) | mantle, highly explosive |
| | D) | oceanic crust, peaceful |
| | E) | oceanic crust, highly explosive |
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13 | |
Basaltic magmas rich in Fe, Mg, Ca and poor in SiO2 are generated mostly by the melting of the ____________ and are erupted mostly as _____________. |
| | A) | asthenosphere, pyroclastic debris |
| | B) | continental crust, pyroclastic debris |
| | C) | continental crust, lava flows |
| | D) | asthenosphere, lava flows |
| | E) | core, lava flows |
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14 | |
In the 1997 movie Volcano there is a violent volcanic eruption in Los Angeles. This is not realistic because _________________. |
| | A) | this area is cut by a strike-slip fault system which typically has no associated volcanic eruptions |
| | B) | this area is an oceanic-oceanic subduction zone which typically has no associated volcanic eruptions |
| | C) | this area is an oceanic-continental subduction zone which typically has no associated volcanic eruptions |
| | D) | this area is a continent-continent collision zone which typically has no associated volcanic eruptions |
| | E) | this area is hot spot zone which typically has no associated volcanic eruptions |
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15 | |
An explosive and catastrophic volcanic eruption is least likely to occur ________________. |
| | A) | at a subduction zone such as Japan |
| | B) | at continental hot spots such as Yellowstone National Park |
| | C) | in the Hawaiian Islands |
| | D) | in rift zones within continental crust such as the Rio Grande Rift |
| | E) | An explosive eruption is equally likely to occur at any of the above locations. |
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16 | |
Why are rhyolitic magmas generally more explosive than basaltic magmas? |
| | A) | The lower silica content and higher temperatures of rhyolitic magma allow the gas to escape easily. |
| | B) | The higher silica content and higher temperatures of rhyolitic magma allow the gas to escape easily. |
| | C) | The higher silica content and lower temperatures of rhyolitic magma allow the gas to escape easily. |
| | D) | The higher silica content and higher temperatures of rhyolitic magma make it difficult for the gas to escape. |
| | E) | The higher silica content and lower temperatures of rhyolitic magma make it difficult for the gas to escape. |
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17 | |
Why do people tend to inhabit areas with high potential for volcanic eruption? |
| | A) | These areas generally have fertile soils. |
| | B) | These areas generally have phenomena such as hot springs that attract people. |
| | C) | The period between major eruptions is generally so long that people become complacent about the dangers. |
| | D) | These areas typically are beautiful settings. |
| | E) | all of the above |
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18 | |
When a volcanic cone collapses into its magma reservoir it forms a ________________. |
| | A) | shield volcano |
| | B) | stratovolcano |
| | C) | scoria cone |
| | D) | caldera |
| | E) | fissure eruption |
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19 | |
The type of magma erupted on the Hawaiian Islands is predominantly basaltic. What type of volcanic landform do you expect to find on the islands? |
| | A) | stratovolcanoes |
| | B) | scoria cones |
| | C) | shield volcanoes |
| | D) | lava domes |
| | E) | answers B and C |
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20 | |
In the 1997 movie Dante's Peak, the final eruption of the stratovolcano blasted a huge cloud of ash and dust high into the atmosphere which then collapsed down the flanks of the mountain under the force of gravity. The style of the eruption portrayed would be best interpreted as _______ which created a _______. |
| | A) | Plinian, pyroclastic flow |
| | B) | Strombolian, lava flow |
| | C) | Pelean, lava flow |
| | D) | Hawaiian, pyroclastic flow |
| | E) | Plinian, lahar |
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21 | |
Mt. Vesuvius and other volcanoes in the Mediterranean region have formed because of _____________. |
| | A) | rifting of Africa from Europe |
| | B) | subduction of the Mediterranean sea floor beneath Europe |
| | C) | a hot spot |
| | D) | continent-continent collision between Africa and Europe |
| | E) | strike-slip fault movement |
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22 | |
In places such as Mt. Pinatubo, people were evacuated from a large area before the eruption. Yet in Hawaii volcanic eruptions occur frequently, and eruption-viewing has become a major tourist attraction. Why? |
| | A) | Most of the magma erupted on Hawaii is in the form of lava flows. |
| | B) | Violent gas-charged eruptions are not common on Hawaii. |
| | C) | The viscosity of magma erupted on Hawaii is generally very low. |
| | D) | Hawaii lies over a hot spot where magma comes from melting of the mantle. |
| | E) | all of the above |
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23 | |
The Earth's outer core is thought to be a highly viscous zone of liquid iron. However, liquid iron never rises from this zone to erupt as molten iron on the surface of the Earth. What is a plausible explanation for this observation? |
| | A) | The temperature of liquid iron from the core is so low that it crystallizes in the lower mantle. |
| | B) | The density of iron liquid in the core is higher than the overlying mantle rocks. |
| | C) | The density of iron liquid in the core is lower than the overlying mantle rocks. |
| | D) | The density of iron liquid in the core is the same as the overlying mantle rocks. |
| | E) | Molten iron is too viscous to flow. |
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24 | |
Magma viscosity increases with _______________. |
| | A) | Increasing temperature, increasing silica (SiO2) content, and increasing crystal content |
| | B) | Decreasing temperature, increasing silica (SiO2) content, and increasing crystal content |
| | C) | Decreasing temperature, decreasing silica (SiO2) content, and decreasing crystal content |
| | D) | Increasing temperature, decreasing silica (SiO2) content, and decreasing crystal content |
| | E) | Decreasing temperature, increasing silica (SiO2) content, and decreasing crystal content |
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25 | |
In order from least explosive to most explosive, eruptions can be described as _________________. |
| | A) | Plinean, Hawaiian, Icelandic |
| | B) | Hawaiian, Strombolian, Plinian |
| | C) | Vulcanian, Icelandic, Strombolian |
| | D) | Strombolian, Plinian, Vulcanian |
| | E) | Icelandic, Volcanian, Hawaiian |
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26 | |
When magma viscosity, volatiles, and volume are all high, a common landform that can result is _______________. |
| | A) | a shield volcano |
| | B) | a scoria cone |
| | C) | a lava dome |
| | D) | a caldera |
| | E) | a fissure |
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27 | |
When magma viscosity and volatiles are low but magma volume is extremely large, a ______________ is likely to result. |
| | A) | flood basalt eruption |
| | B) | caldera |
| | C) | stratovolcano |
| | D) | scoria cone |
| | E) | lava dome |
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