Deck 9: The Wrath of Vulcan: Volcanic Eruptions

Question 1

Columnar joints form when ________.

A) a lava flow cools very rapidly,causing the flow to shatter in a chaotic pattern
B) a lava flow encounters groundwater,which causes the flow to rapidly fracture
C) a lava flow erupts under deep water
D) during the final stages of cooling,a lava flow contracts,forming tall polygonal fractures

Answer 1

D

Question 2

Common volcanic gases include the following:

A) water vapor,carbon dioxide,and sulfur dioxide.
B) oxygen,ozone,and water vapor.
C) oxygen,hydrogen,and argon.
D) carbon dioxide,carbon monoxide,and oxygen.

Answer 2

A

Question 3

The image below shows a lava dome in Panum Crater,California.What is the most likely composition of the rocks that make up this lava dome?

A) felsic
B) intermediate
C) mafic
D) ultramafic

Answer 3

A

Question 4

Ash,cinders,and blocks are all types of ________.

A) tephra
B) lava flows
C) eruptive styles
D) types of volcanoes

Question 5

______________ are snowball-like lumps of ash formed when ash mixes with water in the air and then sticks together to form small balls.

A) Bombs
B) Accretionary lapilli
C) Lahars
D) Xenoliths

Question 6

The textural term for a basaltic lava flow that has a smooth,ropy appearance is ________.

A) pahoehoe
B) a'a'
C) pumice
D) ignimbrite

Question 7

Basaltic lavas that have rough,rubbly surfaces are called ________.

A) pahoehoe
B) a'a'
C) pumice
D) ignimbrite

Question 8

The pillow basalts in the photo below most likely formed ____________.

A) on dry land at a continental hotspot
B) underwater at a subduction zone
C) on dry land at a continental rift
D) underwater at a mid-ocean ridge

Question 9

Compared to felsic lavas,mafic lavas have a ________.

A) lighter color
B) lower viscosity
C) lower density
D) higher silica content

Question 10

Pele's hair ________.

A) consists of thin strands of basaltic glass
B) consists of lumps of rock that develop polished,streamlined surfaces
C) forms only at the leading edge of basaltic lava flows
D) forms when volcanic ash erupts into a rain cloud

Question 11

The characteristic "rotten egg" smell of many active volcanoes is derived from ________.

A) iron and magnesium within lava
B) carbon dioxide gas
C) stale water within the magma chamber
D) hydrogen sulfide gas

Question 12

Basaltic lavas ________.

A) have low viscosity and low silica content
B) have high viscosity and high silica content
C) are more viscous than rhyolitic lavas
D) typically contain a greater proportion of trapped volatiles than rhyolitic lavas

Question 13

A fast-moving wet slurry consisting of a mixture of water and volcaniclastic debris is termed a ________.

A) lahar
B) pyroclastic flow
C) flood basalt
D) hyaloclastite

Question 14

Volcanic bombs are ________.

A) large pyroclastic fragments that acquire streamlined,polished surfaces in flight
B) explosive bodies of lava with high volatile content
C) volcanic fragments that were already solid rock before being ejected during an eruption
D) used by geologists to set off small eruptions in volcanoes that are deemed potentially dangerous

Question 15

Pillow lavas are most commonly associated with ________.

A) subaerial rhyolitic eruptions
B) subaerial basaltic eruptions
C) submarine rhyolitic eruptions
D) submarine basaltic eruptions

Question 16

In 79 C.E.,the citizens of Pompeii and Herculaneum in the Roman Empire were buried by pyroclastic debris derived from an eruption of ________.

A) Mt.Olympus
B) Olympus Mons
C) Mt.Vesuvius
D) Mt.St.Helens

Question 17

The vertical features preserved in the basalt flow in the image below formed because the lava ________.

A) was moving as it cooled,so it fractured
B) erupted underwater and cooled rapidly,forming many fractures
C) was subjected to shaking from earthquakes,and subsequently fractured
D) shrank as it cooled,forming tall polygonal-shaped fractures

Question 18

The difference between accretionary lapilli and pumice lapilli is that ________.

A) accretionary lapilli are always created in ash falls,whereas pumice lapilli are created in pyroclastic flows
B) accretionary lapilli are formed when ash mixes with water in the air.
C) accretionary lapilli are always felsic to intermediate,whereas pumice lapilli are always mafic
D) accretionary lapilli are formed at stratovolcanoes,while pumice lapilli are formed at cinder cones

Question 19

Viscous lava that accumulates above a vent in a bulbous mass creates a ________________

A) shield volcano.
B) stratovolcano.
C) cinder cone.
D) lava dome.

Question 20

Lithified ash (or ash mixed with pyroclastic fragments)forms a volcaniclastic rock called a:

A) tephra
B) scoria
C) lapilli
D) tuff

Question 21

Of the three primary forms of subaerial volcanoes,________ consist of a cone-shaped pile of tephra often formed in a single eruption.

A) stratovolcanoes
B) cinder cones
C) shield volcanoes
D) fissure volcanoes

Question 22

As compared to subaerial basaltic lavas,submarine basaltic lavas differ in that they ________.

A) produce violent pyroclastic debris flows
B) produce large crystals of pyroxene and plagioclase
C) form pillow-like mounds because they cannot flow as far from their source
D) form long but irregular sheets of a'a'

Question 23

Nonviolent eruptions characterized by extensive flows of basaltic lava are termed ________.

A) pyroclastic
B) effusive
C) explosive
D) Plinean

Question 24

Phreatic eruptions take place when ________.

A) volatiles effervesce prior to lava flow
B) groundwater interacts with magma
C) basaltic lava clogs the eruptive vent
D) lava or pyroclastic debris erupts by bursting through the sides of the volcano

Question 25

If a volcano was actively releasing a large amount of volcanic gas and then abruptly stopped,what might happen to the volcano in the near future?

A) It will become extinct because the magma supply has been rapidly withdrawn.
B) It will erupt effusively because the supply of volcanic gas has dissipated.
C) It will erupt explosively because the volcanic gases have no way to escape slowly.
D) It will erupt effusively because the gases have made the magma less viscous.

Question 26

Which volcanic hazard poses the greatest threat to humans?

A) flowing lava
B) volcanic gas
C) falling ash
D) pyroclastic flows

Question 27

The Hawaiian island chain is an example of a(n)________.

A) island volcanic arc
B) continental volcanic arc
C) hot-spot island chain
D) stratovolcanic assembly

Question 28

Which of the following is NOT true? Hot-spot volcanoes ________.

A) can form on the ocean floor
B) can form in continental settings
C) can result in large calderas
D) always produce mafic lava flows

Question 29

Volcanism in Iceland is occurring as a result of ________.

A) eruptions along a mid-ocean ridge
B) eruptions from an intraplate hot spot
C) eruptions from a hot spot that sits astride a mid-ocean ridge
D) subduction of an oceanic plate underneath the continental Eurasian Plate

Question 30

Of the three primary forms of subaerial volcanoes,________ have the most gently sloping sides,due to the low viscosity of the basaltic lavas that form them.

A) stratovolcanoes
B) cinder cones
C) shield volcanoes
D) fissure volcanoes

Question 31

Explosive or voluminous eruptions may cause a volcano to subside or collapse into the now-empty magma chamber,producing a broad depression termed a ________.

A) crater
B) lahar
C) caldera
D) fissure

Question 32

Which of the following does NOT influence whether an eruption will produce lava flows or pyroclastic debris?

A) viscosity of magma
B) composition of magma
C) proportion of volatiles within magma
D) depth and residence time of magma

Question 33

A mixture of air,hot ash,and pumice lapilli that rushes down the side of a volcano in a scalding avalanche is termed a(n)________.

A) ash fall
B) lahar
C) pyroclastic flow
D) convective plume

Question 34

Which of the following magma compositions are most commonly erupted in continental arc settings?

A) basalt
B) rhyolite
C) andesite and rhyolite
D) basalt and andesite

Question 35

A passive eruption that primarily forms lava flows and minor scoria is termed a __________________ eruption.

A) Hawaiian
B) Strombolian
C) Vulcanian
D) Plinean

Question 36

What magma properties would most likely lead to the formation of a shield volcano?

A) low viscosity and mafic composition
B) high viscosity and felsic composition
C) any magma composition so long as it contains a large portion of dissolved volatiles
D) an intermediate composition magma that encounters seawater in the magma chamber

Question 37

A large,violent,explosive eruption is termed a __________________ eruption.

A) Hawaiian
B) Strombolian
C) Vulcanian
D) Plinean

Question 38

The Columbia River Plateau is an example of a ________.

A) caldera
B) fissure
C) flood basalt
D) hot spot

Question 39

Rhyolite lavas ________.

A) do not flow as far from the vent as basaltic lavas do
B) are commonly found at oceanic hot spots
C) are associated with volcanoes that almost never emit pyroclastic debris
D) are commonly found on shield volcanoes

Question 40

Of the three primary forms of subaerial volcanoes,________ are large cone-shaped mountains that consist of alternating layers of tephra and solidified lava.

A) stratovolcanoes
B) cinder cones
C) shield volcanoes
D) fissure volcanoes

Question 41

Describe how an explosive volcanic eruption can create a global cooling event.

Question 42

Describe how explosive eruptions occur.Make sure to address viscosity,gas content,and the process for building pressure.

Question 43

What is a caldera? How is a caldera different from a stratovolcano?

Question 44

What was unusual about the 1986 volcano-related disaster near Lake Nyos in Cameroon?

A) A volcanic eruption involved a lateral blast of volcaniclastic debris that no one anticipated.
B) Pyroclastic flows buried surrounding villages,reminiscent of Pompeii ~1,900 years earlier.
C) Volcanically derived carbon dioxide gas bubbled from the lake and suffocated people and animals nearby.
D) A slurry of lava and lake water flowed rapidly outward from the lake and buried surrounding villages.

Question 45

The largest known volcanic eruption in the last million years occurred at ________.

A) Toba Volcano (Indonesia)
B) Mt.St.Helens (USA)
C) Mt.Pinatubo (Philippines)
D) Yellowstone Caldera (USA)

Question 46

What is the fundamental difference between an explosive and an effusive eruption? What variables are important in determining whether a volcano "flows" or "blows"?

Question 47

Volcanoes have provided some positive benefits to humankind and life in general throughout geologic time.Which of the following is NOT true about volcanoes?

A) Volcanic eruptions can enrich soils,making land more fertile.
B) Volatiles from volcanoes provided much of our early oceans' water.
C) Volcanic eruptions have prevented several mass extinctions by cooling the Earth's climate.
D) Gases from volcanic eruptions provided much of the content of the early atmosphere.

Question 48

Is it possible for scientists to predict eruptions? What are two ways in which geoscientists look for possible volcanic activity in the short term?

Question 49

What are the three main types of volcanoes? How is the shape of a volcano related to its eruptive style?

Question 50

If a volcano lies along a convergent boundary but has not erupted in over 100,000 years,the volcano is considered ________.

A) active
B) dormant
C) extinct
D) dead

Question 51

How do volcanic eruptions affect global average temperatures on the Earth?

A) Aerosols block incoming solar radiation.
B) Ash traps heat in atmosphere.
C) Ash and aerosols block incoming solar radiation.
D) Greenhouse gases block incoming solar radiation.

Question 52

The style of eruption depends on the plate tectonic setting in which the volcano is situated.Compare the different eruption styles you would observe at a divergent versus a convergent plate boundary.Make sure to address the role composition,viscosity,and gas content play in your answer.

Question 53

Olympus Mons,the largest known volcano in our Solar System,is found on ________.

A) Earth
B) Mars
C) Venus
D) Io,a moon of Jupiter

Question 54

In 1902,a famous pyroclastic flow killed approximately 28,000 people on the Caribbean island of ________.

A) Puerto Rico
B) Martinique
C) Aruba
D) Jamaica

Question 55

Olympus Mons,the largest known volcano in our Solar System,is an example of a ________.

A) stratovolcano
B) cinder cone
C) shield volcano
D) fissure volcano

Question 56

Recurrence intervals are often used as estimates of when the next eruption might occur.Explain what a recurrence interval is and how it is calculated.Why is a recurrence interval not the most useful means of forecasting eruptions?

Question 57

Describe the difference between the relative viscosity of felsic versus mafic magma and how this affects the rate of flow of each type.

Question 58

List and describe two volcanic hazards,including both a description of the hazard and the possible effects of the hazard.

Question 59

Volcanologists and geologists monitor volcanoes to determine whether or not an eruption is imminent.Which of the following is not a typically used monitoring technique?

A) earthquake activity
B) changes in velocity of streams flowing from around the volcano
C) changes in the shape of the volcano
D) increases in gas and steam emissions

Question 60

The average time between eruptions is called a(n)________.

A) recurrence interval
B) prediction
C) forecast
D) assessment