Deck 4: Volcanoes and Volcanism

Question 1

Volcanic smog forms by reaction of:

A) sulfur dioxide with oxygen.
B) sulfur dioxide with sulfur crystals.
C) sulfur dioxide with Carbon dioxide.
D) sulfur dioxide with water.

Answer 1

D

Question 2

Direct evidence of volcanism has been discovered on all of the following EXCEPT:

A) the Moon.
B) Mars.
C) Venus.
D) Saturn.

Answer 2

D

Question 3

Deep water eruptions (below about 300 meters) display a characteristic structure called:

A) pillows.
B) 'a'a.
C) columnar jointing.
D) pahoehoe.

Answer 3

A

Question 4

The greatest danger from a subglacial eruption is:

A) explosive steam eruptions.
B) outburst floods.
C) suffocating ash clouds.
D) extensive lava fountains and flows.

Question 5

Volcanoes are beneficial to humanity in many ways. All of the following are benefits EXCEPT:

A) volcanoes give scientists insight into subterranean rock composition.
B) some gases released by volcanoes are toxic to humans.
C) many volcanic soils prove fertile for agriculture.
D) some volcanoes provide sources of clean energy.

Question 6

All of the following are somewhat effective means of dealing with volcanic hazards EXCEPT:

A) cooling a lava front with water.
B) bombing of lava flows.
C) plugging a volcano's vent.
D) accurately predicting a volcanic eruption.

Question 7

Shield volcanoes are most likely to form from:

A) pyroclastic ash- flow eruptions.
B) culminating pyroclastic eruptions.
C) effusive eruptions from a central vent.
D) effusive eruptions from a fissure.

Question 8

All of the following events could indicate an impending eruption EXCEPT:

A) a highly eroded, volcanic peak.
B) discovery of new hot springs around the volcano.
C) swarms of small earthquakes in the region.
D) a measurable bulge or swelling of the volcano.

Question 9

A volcanic dome forms when:

A) faulting causes uplift of a volcano.
B) a large volcanic mountain is rounded off by erosion.
C) rising magma cools and hardens within a volcano's crater.
D) a shield volcano takes on a relatively symmetrical dome shape.

Question 10

The force that causes pyroclastic volcanoes to explode violently is:

A) density differences within the magma that force part of the magma upward.
B) pressure from volcanic gases.
C) chemically volatile substances that explode within the magma.
D) hot convection currents in the asthenosphere that push magma upward.

Question 11

Felsic magmas with high water and gas content commonly form:

A) 'a'a.
B) columnar jointing.
C) pumice.
D) pahoehoe.

Question 12

If a volcano has not erupted in the past few thousand years, but is likely to erupt sometime in the future, it is considered to be:

A) active.
B) extinct.
C) dormant.
D) none of the above.

Question 13

All of the following statements concerning magma movement are true EXCEPT:

A) a highly viscous magma usually crystallizes at lower temperatures.
B) the gases in low- viscosity magmas tend to escape easily when the magma reaches the surface.
C) as heat reduces viscosity, ions within a magma move more rapidly.
D) a very viscous magma tends to be less explosive.

Question 14

A lahar can best be described as a:

A) flow of hot lava.
B) volcanic mudflow.
C) flow of gas and hot ash.
D) rain of tephra particles.

Question 15

Which of the following is a likely product of a subaqueous basaltic eruption?

A) 'A'a.
B) Pillow structures.
C) Pumice.
D) Pahoehoe.

Question 16

Which of the following statements regarding volcanoes is NOT true?

A) Basaltic volcanoes have more gentle slopes than rhyolitic volcanoes.
B) Violent volcanoes tend to occur at convergent plate boundaries, whereas gentle volcanoes tend to occur at divergent plate boundaries.
C) Rhyolitic volcanoes usually form calderas, while basaltic volcanoes form shield cones.
D) Magma of gentle volcanoes has a higher silica content and a higher viscosity than magma of violent volcanoes.

Question 17

An active volcano is any volcano that:

A) is currently erupting or has erupted recently (in geological terms).
B) has not been worn away by erosion.
C) has not erupted recently (in geological terms) but is likely to erupt in the future.
D) is located on an active tectonic plate boundary.

Question 18

Pyroclastic eruptions are likely to occur in all of the following locations EXCEPT:

A) along transform boundaries.
B) above subducting plate boundaries.
C) above continental intraplate hot spots.
D) within intracontinental rift zones.

Question 19

The greatest danger to Hawai'i from the undersea volcano Loihi is:

A) earthquake swarms.
B) explosive steam eruptions.
C) tsunamis.
D) ash- flow eruptions.

Question 20

All of the following are true regarding tephra EXCEPT:

A) volcanic ash is coarser than volcanic dust.
B) tephra may consist of sizable blocks of solidified lava known as volcanic bombs.
C) tephra is usually formed under water.
D) coarser- grained tephra deposits are usually nearer the volcanic source.

Question 21

Which of the following characteristics would you NOT expect from an effusive eruption?

A) Central vent and fissures are the lava source.
B) Flows of basaltic lava.
C) Quiet, nonexplosive eruption event.
D) Large volumes of pyroclastic materials produced.

Question 22

Which of the following is composed of six- sided polygonal columns of rock?

A) Columnar jointing.
B) Pahoehoe lava flow.
C) Nue^´e ardente.
D) 'A'a lava flow.

Question 23

A volcano can spew several kinds of gases into the air, but most of the gas is:

A) nitrogen and carbon dioxide.
B) nitrogen and sulfur dioxide.
C) water vapor and carbon dioxide.
D) sulfur dioxide and chlorine.

Question 24

A welded tuff forms when:

A) hot lava flows over rocks, causing them to become metamorphic.
B) semi- molten volcanic bombs fuse together.
C) particles within a lahar cool and crystallize.
D) particles within a nue´e ardente cool and crystallize.

Question 25

What volcanic phenomenon occurred during recent eruptions of Montserrat's Soufriere Hills volcano?

A) Explosive eruptions of volcanic ash.
B) Toxic gases covered the island.
C) Island was blanketed in volcanic mudflows.
D) Numerous lava flows scorched the island.

Question 26

Why is basalt more common than gabbro, but rhyolite less common than granite?

A) The silica content of rhyolitic lavas is less than basaltic lavas.
B) Rhyolitic lavas are hotter than basaltic magmas.
C) Basaltic lavas are less viscous than rhyolitic lavas.
D) Basaltic lavas are more viscous than rhyolitic lavas.

Question 27

Which of the following is LEAST likely to be a product of a volcano with an andesitic lava?

A) Pillow structures.
B) 'A'a.
C) Pahoehoe.
D) Columnar jointing.

Question 28

What is the most common way of predicting volcanic eruptions?

A) Abnormal animal behavior.
B) Harmonic tremors.
C) Drop in sea level.
D) Water wells suddenly dry up.

Question 29

Which magma type produces the most lava flows?

A) Basaltic.
B) Rhyolitic.
C) Andesitic.
D) None of the above.

Question 30

A nue´e ardente can best be described as a:

A) flow of trapped air.
B) flow of hot pyroclastic material.
C) rain of tephra particles.
D) flow of hot lava.

Question 31

Compared to rhyolitic lavas, basaltic lavas tend to be:

A) higher in viscosity and retain dissolved gases.
B) higher in viscosity but easily release dissolved gases.
C) lower in viscosity and easily release dissolved gases.
D) lower in viscosity and retain dissolved gases.

Question 32

Whether they are basaltic or rhyolitic, almost all volcanoes have both:

A) volcanic domes and calderas.
B) volcanic cones and craters.
C) lava flows and ash flows.
D) pahoehoe and aa flows.

Question 33

Of the following, the magma with the highest viscosity would have:

A) a high silica content and low temperature.
B) a high silica content and high temperature.
C) a low silica content and high temperature.
D) a low silica content and low temperature.

Question 34

An effusive eruption from a fissure would most likely result in:

A) a composite cone.
B) a shield cone.
C) a cinder cone.
D) a flood basalt.

Question 35

The principal factor(s) influencing upward magma migration before cooling is (are):

A) the climate and temperature regime that affects the land surrounding the volcano.
B) the time since the last eruption, combined with the density of the rocks overlying the volcano.
C) the magmatic gas content, combined with magma viscosity.
D) the magmatic water content.

Question 36

A pyroclastic volcanic eruption in which there is no volcanic cone but tephra is expelled from a series of ring- like fractures is called a(n):

A) effusive eruption.
B) culminating eruption.
C) fissure eruption.
D) ash- flow eruption.

Question 37

The term viscosity refers to:

A) how a liquid moves upward against gravity.
B) how heat and pressure influence a liquid's gas content.
C) how dense a liquid is.
D) a liquid's resistance to flow.

Question 38

Which of the following events would you NOT expect from the gigantic Toba ash- flow eruption?

A) Worldwide drop in human populations.
B) Burial of Asia under a thick blanket of ash.
C) Worldwide rise in sea level.
D) Initiation of a six- year- long global "volcanic winter."

Question 39

The most quiet and least dangerous volcanic eruptions involve:

A) glowing avalanches of volcanic rock fragments.
B) fountains and flowing streams of lava.
C) showers of fine ash particles.
D) fallout of volcanic blocks the size of automobiles.

Question 40

What rock type blocked ships after the eruption of Krakatau in 1883?

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

Question 41

All of the following are likely environmental effects of a volcanic explosion EXCEPT:

A) acid precipitation.
B) decreased global temperatures.
C) decreased sunlight.
D) an increased growing season.

Question 42

Which of the events associated with the Toba eruption most affected human populations?

A) Elimination of food sources.
B) Worldwide fall in sea level.
C) One- thousand- year- long glacial expansion.
D) Widespread cold weather.

Question 43

Describe the differences in the volcanic products of basaltic and rhyolitic volcanoes.

Question 44

Discuss two of the secondary environmental effects associated with volcanic eruptions.

Question 45

Why is the Olympus Mons volcano on Mars so much larger than similar shield volcanoes on Earth?

Question 46

Discuss three methods for coping with volcanic hazards.

Question 47

What are ash- flow eruptions?

Question 48

Describe the differences between the plate- tectonic settings of rhyolitic and basaltic volcanoes.

Question 49

How do volcanic craters form?

Question 50

Explain why felsic magmas have a higher viscosity and retain gases more than mafic magmas.

Question 51

How did the cataclysmic eruption of Krakatau in 1883 affect global climate?

Question 52

Discuss why efforts to predict volcanic eruptions sometimes fail.