Deck 5: Volcanoes

Question 1

A significant portion of what is erupted by a volcano is gas.Water vapor represents the largest percentage of the total volume of gas erupted.This gas represents the second largest percentage of the total gas volume

A) Sulfur dioxide.
B) Nitrogen dioxide.
C) Carbon dioxide.
D) Carbon monoxide.

Answer 1

C

Question 2

Pyroclastics

A) Represent the fluid portion of lavas.
B) Are solid materials erupted from a volcano.
C) Are smaller volcanos that develop on the sides of a main volcano.
D) Are researchers who study volcanos and volcanic processes.

Answer 2

B

Question 3

Which of the following is a good example of a shield volcano

A) Mt. St. Helens.
B) Andes mountains.
C) Cascade mountains.
D) Hawaiian islands.

Answer 3

D

Question 4

Which of the following volcanoes is least likely to erupt violently and explosively?

A) Kilauea on Hawaii
B) Mount St. Helens in the Cascades
C) Mount Augustine in the Aleutians
D) Mt. Pinatubo in the Philippines

Question 5

Eruption of magma from a long crack in the lithosphere is a

A) Pyroclastic eruption.
B) Nuée ardente.
C) Fissure eruption.
D) Cascade volcano.

Question 6

Rather than freely spreading,if the lava piles up close to the vent resulting in a structure that is steep-sided and compact is called a

A) Volcanic dome.
B) Plutonic dome.
C) Volcanic basin.
D) Lava dome.

Question 7

A volcanic landform built of entirely of pyroclastics of basaltic composition is a

A) Shield volcano.
B) Cinder cone.
C) Volcanic dome.
D) Nuée ardente.

Question 8

A volcano built of many thin flows of fluid lava is a

A) Shield volcano.
B) Composite volcano.
C) Cinder cone.
D) Subduction-zone volcano.

Question 9

A phreatic volcanic eruption

A) Involves ash only.
B) Is the same type of eruption as a nuée ardente.
C) Only occurs at rift zones.
D) Results from groundwater that becomes steam upon magmatic heating.

Question 10

Fast moving volcanic mudflow is formed as a result of the combination of water and volcanic ash results in

A) Lahars.
B) Pyroclastic flows.
C) Cinder cones.
D) Lava domes.

Question 11

In contrast to the mafic volcanism at rift zones,subduction zone lavas are lower in iron content but significantly higher in these

A) Magnesium and silica.
B) Water and silica.
C) Water and magnesium.
D) Calcium and silica.

Question 12

Strategies for stopping an advancing lava flow include all of the following except

A) Spraying water on the flow front to cool it.
B) Constructing a dense, massive plug to stop up the vent from which the magma is erupting.
C) Using explosives to punch holes selectively in a flow's hardened crust to divert remaining liquid lava.
D) All of these are strategies for stopping an advancing lava flow.

Question 13

The low-viscosity,fluid lava of hot-spot volcanoes is typically

A) Felsic.
B) Intermediate.
C) Mafic.
D) Ultramafic.

Question 14

The 1883 Krakatoa,Indonesia eruption is more accurately classified as an

A) Effusive eruption.
B) Pyroclastic eruption.
C) Phreatic eruption.
D) None of the choices are correct.

Question 15

Volcanic ash

A) Is composed of microscopic shards of volcanic glass.
B) Is soot formed when hot lava causes plants to burn.
C) Is the same size as cinder.
D) Is only erupted by rift zone volcanoes.

Question 16

The Pacific Ring of Fire is

A) A nearly circular region of fissure eruptions in the Pacific Ocean basin.
B) Volcanic activity related to subduction zones and spreading zones rimming the Pacific Ocean basin.
C) A region of nearly continuous eruption of nueé ardentes in the Pacific Ocean basin.
D) The region defined by the Hawaiian Islands and the adjacent underwater volcanoes known as seamounts.
E) A doughnut-shaped eruption characteristic of Pacific Islands, which, when dormant is called an atoll.

Question 17

A hot,glowing cloud of gas and ash is sometimes known as a

A) Nuée ardente.
B) Lahar.
C) Rhyolite.
D) Composite flow.

Question 18

Volcanic rocks are

A) Crystallized from magma at or near the earth's surface.
B) By definition, only those produced by conelike volcanic structures.
C) Coarse-grained because the magmas typically spend so long inside the volcano before eruption.
D) All of the choices are correct.

Question 19

Mafic magmas

A) May contain up to about 75 percent SiO₂ by weight.
B) Are viscous and do not flow easily.
C) Tend to inhibit passage of gas that tries to escape through it.
D) Result in less violent eruptions than felsic to intermediate magmas.

Question 20

The rock type that forms at new seafloor spreading centers is

A) Andesitic.
B) Rhyolitic.
C) Granitic.
D) Basaltic.

Question 21

Each volcano has a characteristic eruptive style; the nature of past eruptions indicates whether or not a particular volcano is likely to erupt violently in the future.

Question 22

To halt a pyroclastic flow,one could use many of the same techniques as are used for lava,because both are flowing fluids.

Question 23

The path of a lava flow can to some extent be predicted; like any fluid,lava flows downhill.

Question 24

A caldera is

A) A topographically low area that results from the collapse of a volcano after its magma chamber empties or removal of the top of a volcano during an explosive eruption.
B) An alternate name for boiling mud pots in thermally active areas.
C) Not associated with andesitic or rhyolitic volcanism, but only with basaltic volcanism.
D) Only preserved for short periods of time, so that ancient calderas do not exist.

Question 25

A dormant volcano that is currently inactive could have a potential to possibly become active.

Question 26

The Volcanic Explosivity Index (VEI)is based on

A) The length of the eruption.
B) The volume of pyroclastics produced.
C) The height to which the pyroclastics rose in the atmosphere.
D) All the choices are correct.

Question 27

Volcanoes that build domes are more likely to erupt explosively than are shield volcanoes.

Question 28

The type of volcano most likely to form over an oceanic "hot spot" is a

A) Composite volcano.
B) Volcanic dome.
C) Shield volcano.
D) Stratovolcano.

Question 29

The 1991 eruption of Mt.Pinatubo caused global cooling because it

A) Added ozone to the ozone layer.
B) Produced sulfuric acid droplets in the atmosphere that blocked incoming sunlight.
C) Caused increased evaporation of cool water vapor from the oceans.
D) Produced very strong winds that cooled the continents.

Question 30

The Cascade Range volcanoes

A) Sit above a subduction zone.
B) Are now expected to become extinct as they cool.
C) Pose little threat, as their eruptions are typically quiet ones.
D) All of the choices are correct.

Question 31

A volcanic rock of intermediate composition,characteristic of subduction-zone volcanoes like those of the Cascade Range is

A) Basalt.
B) Andesite.
C) Rhyolite.
D) Granite.

Question 32

Mount St.Helens and the related Cascade Range volcanoes represent the only volcanically active areas in the United States.

Question 33

The Soufriere Hills volcano on Montserrat in the Caribbean

A) Is a good example of a shield volcano.
B) Is a good example of a stratovolcano.
C) Is formed by a rift zone.
D) Is an unusually large cinder cone.

Question 34

Yellowstone National Park is underlain by an ancient volcanic caldera and current thermal activity and uplift there may signal future eruption potential.

Question 35

Possible precursors of volcanic eruptions include.

A) Bulging, tilt or uplift of the volcano's surface.
B) Increased seismic activity.
C) Changes in composition of gases escaping from the volcano.
D) All of the choices are correct.

Question 36

Of the following volcanic landforms,one that is a stratovolcano

A) Any one of the Azores Islands, Portugal.
B) Mt. Hood, Oregon.
C) Any one of the Hawaiian Islands.
D) Sunset Crater, Arizona.

Question 37

Volumetrically,the greatest production of new volcanic rock occurs at seafloor spreading ridges.

Question 38

The so-called Ring of Fire rimming the Pacific Ocean is really a ring of subduction zones.

Question 39

The largest and most violent Cascade volcano eruption was that of Mt.St.Helens in 1980.

Question 40

Active periods in a volcano's history

A) Typically involve only one significant eruptive phase lasting days or, at most, a few weeks.
B) Always begin with a nuée ardente.
C) May occur at intervals of hundreds or thousands of years, with quiet periods in between.
D) All of the choices are correct.

Question 41

Of the following: various sulfur gases,hydrochloric acid,and carbon monoxide,only carbon monoxide is poisonous.

Question 42

Increased thermal activity (fumaroles,hot springs)in a volcanic area may signal the presence of hot magma at shallow depths in the crust.

Question 43

Explosive volcanoes can be so unpredictable that even volcanologists monitoring and studying them can be killed by unexpected eruptions.

Question 44

People can be killed by poisonous gases emitted by a volcano even before they realize that they are in danger.

Question 45

The passage of magma up through the lithosphere may be traced by the shallowearthquake focal depths over time.

Question 46

The damage from ash fall in the eruption of Mt.Pinatubo,Philippines in 1991 would have been worse,but fortunately,monsoon rains washed the ash off houses and hillsides.

Question 47

The Yellowstone Park volcanic area is along a hot-spot track across the northwestern United States.

Question 48

So far,Mount St.Helens is the only volcano in the Cascade Range to show any sign of thermal activity.

Question 49

A major concern about possible future eruptions of Mount Rainier is the potential for mudflow damage to nearby cities.

Question 50

Volcanic ash from recent eruptions of Aleutian volcanoes has posed a threat to air travel.

Question 51

Construction on any active or dormant volcano in the United States is now prohibited by law because it would be so dangerous.