Question 1

The dominant volcanic gas (commonly 90% or more of total gas)is _____________.

Accepted Answer

A) water vapor (H2O) 
B) carbon dioxide (CO2) 
C) sulfur dioxide (SO2) 
D) hydrogen sulfide (H2S)with its rotten egg smell 
E) carbon monoxide (CO) 
A) water vapor (H2O) 
B) carbon dioxide (CO2) 
C) sulfur dioxide (SO2) 
D) hydrogen sulfide (H2S)with its rotten egg smell 
E) carbon monoxide (CO) A

Question 2

Why does the magma from some volcanoes flow smoothly and relatively peacefully,while the magma from other volcanoes blasts forth violently and deals death over wide areas?

Accepted Answer

A) differences in the chemical and mineral makeup of magmas 
B) variations in the temperature,water and gas content,and viscosity of magmas 
C) different geographic positions with respect to hot spots and edges of tectonic plates 
D) All of these are correct. 
A) differences in the chemical and mineral makeup of magmas 
B) variations in the temperature,water and gas content,and viscosity of magmas 
C) different geographic positions with respect to hot spots and edges of tectonic plates 
D) All of these are correct. D

Question 3

Spreading centers are an ideal location for volcanism because ______________.

Accepted Answer

A) they sit above the high-temperature asthenosphere 
B) the asthenosphere rock has low percentages of SiO2 
C) the oceanic plates pull apart causing hot asthenosphere rock to rise and undergo decompression melting to form magma that continues to rise 
D) All of the choices are correct. 
A) they sit above the high-temperature asthenosphere 
B) the asthenosphere rock has low percentages of SiO2 
C) the oceanic plates pull apart causing hot asthenosphere rock to rise and undergo decompression melting to form magma that continues to rise 
D) All of the choices are correct. D

Question 4

At oceanic spreading centers,magmas are rhyolitic in composition.

Accepted Answer

A) True 
 B)False

Question 5

__________ are steep-sided,symmetrical volcanic peaks built of alternating layers of pyroclastic debris capped by high-viscosity andesitic to rhyolitic lava flows that solidify to form protective caps.

Accepted Answer

A) Stratovolcanoes 
B) Scoria cones 
C) Shield volcanoes 
D) Calderas 
A) Stratovolcanoes 
B) Scoria cones 
C) Shield volcanoes 
D) Calderas

Question 6

When magma nears the surface,gases come out of solution and help cause volcanic eruption.

Accepted Answer

A) True 
 B)False

Question 7

At a depth of 20 miles,basaltic rock melts at around 1400$\circ$C but this same rock will melt at only 1250$\circ$C at the Earth's surface.

Accepted Answer

A) True 
 B)False

Question 8

If lava reaches the sea or a lake it cools rapidly into ovoid or toothpaste-looking forms called pillow lava.

Accepted Answer

A) True 
 B)False

Question 9

Basaltic magma has the lowest viscosity,so more of it reaches the surface;the more viscous rhyolitic magmas are so sluggish that they tend to be trapped deep below the surface where they cool,solidify,and grow into the larger mineral crystals of plutonic rocks.

Accepted Answer

A) True 
 B)False

Question 10

Eruptions in Hawaii are always peaceful.

Accepted Answer

A) True 
 B)False

Question 11

Hot spots occur only under oceanic plates.

Accepted Answer

A) True 
 B)False

Question 12

If basaltic lava reaches the sea or a lake,it cools rapidly into ____________.

Accepted Answer

A) bed lava 
B) sheet lava 
C) blanket lava 
D) pillow lava 
A) bed lava 
B) sheet lava 
C) blanket lava 
D) pillow lava

Question 13

A scoria cone is likely to form if lava is low in gas content and high in viscosity.

Accepted Answer

A) True 
 B)False

Question 14

Mineral growth in magmas at the surface with temperatures around 1000 to 1200$\circ$C occurs in the following way:

Accepted Answer

A) Iron and magnesium will link up with aluminum and the silicon-oxygen tetrahedron as magma temperature decreases to sequentially form four distinct and discontinuous families of minerals-olivine,pyroxene,amphibole,and biotite mica. 
B) Calcium will combine with aluminum and the silicon-oxygen tetrahedron to begin forming the plagioclase feldspar family,a continuous and gradational series of minerals. 
C) Both of these are correct. 
D) Neither of these is correct. 
A) Iron and magnesium will link up with aluminum and the silicon-oxygen tetrahedron as magma temperature decreases to sequentially form four distinct and discontinuous families of minerals-olivine,pyroxene,amphibole,and biotite mica. 
B) Calcium will combine with aluminum and the silicon-oxygen tetrahedron to begin forming the plagioclase feldspar family,a continuous and gradational series of minerals. 
C) Both of these are correct. 
D) Neither of these is correct.

Question 15

The formation of a giant continental caldera includes all but which of the following?

Accepted Answer

A) Rising magma forms a low-density cap rich in SiO2 and gases,bulging the ground surface upward. 
B) Basaltic eruptions begin from circular fractures surrounding the bulge. 
C) Magma pours out in high-volume pyroclastic flows,causing the ground surface to sink into a caldera. 
D) Removal of magma decreases the pressure on the magma below the caldera,causing new magma to bulge up the caldera floor. 
E) All of these are correct. 
A) Rising magma forms a low-density cap rich in SiO2 and gases,bulging the ground surface upward. 
B) Basaltic eruptions begin from circular fractures surrounding the bulge. 
C) Magma pours out in high-volume pyroclastic flows,causing the ground surface to sink into a caldera. 
D) Removal of magma decreases the pressure on the magma below the caldera,causing new magma to bulge up the caldera floor. 
E) All of these are correct.

Question 16

A shield volcano has a great ___________.

Accepted Answer

A) height compared to its width 
B) width compared to its height 
C) amount of pumice 
D) proportion of pyroclastic material,compared with lava flows 
A) height compared to its width 
B) width compared to its height 
C) amount of pumice 
D) proportion of pyroclastic material,compared with lava flows

Question 17

The primary reason magma forms at subduction zones is that the subducting plate carries a cover of sediments,water,and hydrated minerals down with it,which lowers the temperature required for the adjacent overlying mantle lithospheric rock to melt.

Accepted Answer

A) True 
 B)False

Question 18

____________ in the Aegean Sea underwent an explosive series of eruptions around 1628B.C.E.that buried the Bronze Age city of Akrotiri on Thera to depths of 70 meters.

Accepted Answer

A) Vesuvius 
B) Krakatoa 
C) Santorini 
D) Mt.Pele 
A) Vesuvius 
B) Krakatoa 
C) Santorini 
D) Mt.Pele

Question 19

The volcanic explosivity index (VEI)measures size of volcanic eruptions on a scale of 0 to 8.Between 1500 and 1981,one VEI 7 eruption occurred.This was ______________.

Accepted Answer

A) Tambora,in 1815 
B) Krakatau,in 1883 
C) Mt.St.Helens in 1980 
D) Mt.Pelee in 1902 
E) Mt.Vesuvius in 1631 
A) Tambora,in 1815 
B) Krakatau,in 1883 
C) Mt.St.Helens in 1980 
D) Mt.Pelee in 1902 
E) Mt.Vesuvius in 1631

Question 20

_________ eruptions are common first phases in the eruptions of volcanoes as they "clear their throats" before emitting larger eruptions.

Accepted Answer

A) Hawaiian-type 
B) Icelandic-type 
C) Vulcanian-type 
D) Plinian-type 
E) Surtseyan-type 
A) Hawaiian-type 
B) Icelandic-type 
C) Vulcanian-type 
D) Plinian-type 
E) Surtseyan-type

The dominant volcanic gas (commonly 90% or more of total gas)is _____________.

Why does the magma from some volcanoes flow smoothly and relatively peacefully,while the magma from other volcanoes blasts forth violently and deals death over wide areas?

Spreading centers are an ideal location for volcanism because ______________.

At oceanic spreading centers,magmas are rhyolitic in composition.

__________ are steep-sided,symmetrical volcanic peaks built of alternating layers of pyroclastic debris capped by high-viscosity andesitic to rhyolitic lava flows that solidify to form protective caps.

When magma nears the surface,gases come out of solution and help cause volcanic eruption.

At a depth of 20 miles,basaltic rock melts at around 1400^$\circ$C but this same rock will melt at only 1250^$\circ$C at the Earth's surface.

If lava reaches the sea or a lake it cools rapidly into ovoid or toothpaste-looking forms called pillow lava.

Basaltic magma has the lowest viscosity,so more of it reaches the surface;the more viscous rhyolitic magmas are so sluggish that they tend to be trapped deep below the surface where they cool,solidify,and grow into the larger mineral crystals of plutonic rocks.

Eruptions in Hawaii are always peaceful.

Hot spots occur only under oceanic plates.

If basaltic lava reaches the sea or a lake,it cools rapidly into ____________.

A scoria cone is likely to form if lava is low in gas content and high in viscosity.

Mineral growth in magmas at the surface with temperatures around 1000 to 1200^$\circ$C occurs in the following way:

The formation of a giant continental caldera includes all but which of the following?

A shield volcano has a great ___________.

The primary reason magma forms at subduction zones is that the subducting plate carries a cover of sediments,water,and hydrated minerals down with it,which lowers the temperature required for the adjacent overlying mantle lithospheric rock to melt.

____________ in the Aegean Sea underwent an explosive series of eruptions around 1628B.C.E.that buried the Bronze Age city of Akrotiri on Thera to depths of 70 meters.

The volcanic explosivity index (VEI)measures size of volcanic eruptions on a scale of 0 to 8.Between 1500 and 1981,one VEI 7 eruption occurred.This was ______________.

_________ eruptions are common first phases in the eruptions of volcanoes as they "clear their throats" before emitting larger eruptions.

Natural Disasters and the Human Population

Internal Energy and Plate Tectonics

Earthquake Geology and Seismology

Plate Tectonics and Earthquakes

Earthquakes Throughout the United States and Canada

Volcano Processes and Deadly Events

Tsunami Versus Wind-Caused Waves

External Energy Fuels Weather and Climate

Tornadoes, Lightning, Heat, and Cold

Hurricanes

Climate Change

Floods

Fire

Mass Movements

Coastal Processes and Hazards

Impacts With Space Objects

Filters

Exam 6: Volcanic Eruptions: Plate Tectonics and Magmas

The dominant volcanic gas (commonly 90% or more of total gas)is _____________.

Why does the magma from some volcanoes flow smoothly and relatively peacefully,while the magma from other volcanoes blasts forth violently and deals death over wide areas?

Spreading centers are an ideal location for volcanism because ______________.

At oceanic spreading centers,magmas are rhyolitic in composition.

__________ are steep-sided,symmetrical volcanic peaks built of alternating layers of pyroclastic debris capped by high-viscosity andesitic to rhyolitic lava flows that solidify to form protective caps.

When magma nears the surface,gases come out of solution and help cause volcanic eruption.

At a depth of 20 miles,basaltic rock melts at around 1400 ∘\circ∘ C but this same rock will melt at only 1250 ∘\circ∘ C at the Earth's surface.

If lava reaches the sea or a lake it cools rapidly into ovoid or toothpaste-looking forms called pillow lava.

Basaltic magma has the lowest viscosity,so more of it reaches the surface;the more viscous rhyolitic magmas are so sluggish that they tend to be trapped deep below the surface where they cool,solidify,and grow into the larger mineral crystals of plutonic rocks.

Eruptions in Hawaii are always peaceful.

Hot spots occur only under oceanic plates.

If basaltic lava reaches the sea or a lake,it cools rapidly into ____________.

A scoria cone is likely to form if lava is low in gas content and high in viscosity.

Mineral growth in magmas at the surface with temperatures around 1000 to 1200 ∘\circ∘ C occurs in the following way:

The formation of a giant continental caldera includes all but which of the following?

A shield volcano has a great ___________.

The primary reason magma forms at subduction zones is that the subducting plate carries a cover of sediments,water,and hydrated minerals down with it,which lowers the temperature required for the adjacent overlying mantle lithospheric rock to melt.

____________ in the Aegean Sea underwent an explosive series of eruptions around 1628B.C.E.that buried the Bronze Age city of Akrotiri on Thera to depths of 70 meters.

The volcanic explosivity index (VEI)measures size of volcanic eruptions on a scale of 0 to 8.Between 1500 and 1981,one VEI 7 eruption occurred.This was ______________.

_________ eruptions are common first phases in the eruptions of volcanoes as they "clear their throats" before emitting larger eruptions.

Natural Disasters and the Human Population

Internal Energy and Plate Tectonics

Earthquake Geology and Seismology

Plate Tectonics and Earthquakes

Earthquakes Throughout the United States and Canada

Volcano Processes and Deadly Events

Tsunami Versus Wind-Caused Waves

External Energy Fuels Weather and Climate

Tornadoes, Lightning, Heat, and Cold

Hurricanes

Climate Change

Floods

Fire

Mass Movements

Coastal Processes and Hazards

Impacts With Space Objects

Filters

At a depth of 20 miles,basaltic rock melts at around 1400^$\circ$C but this same rock will melt at only 1250^$\circ$C at the Earth's surface.

Mineral growth in magmas at the surface with temperatures around 1000 to 1200^$\circ$C occurs in the following way: