Geology: Lecture Exam #4 (Ch 9: Volcanic Eruptions)

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Ch 9: Volcanic Eruptions

Geology

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124 Terms

1
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What is a volcano?

An erupting vent through which molten rock surfaces

2
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What happened in 79 C.E. at Mount Vesuvius?

Pyroclastic flows destroyed Pompeii, killing 20,000.

3
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What are the three forms of volcanic products mentioned on page 6?

Lava flows, pyroclastic debris, volcanic gases

4
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What factors determine the viscosity of lava?

Composition, especially silica (SiO2), Fe, and Mg content, temperature, gas content, crystal content.

5
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What is the characteristic of mafic lava?

Very hot, low silica, and low viscosity

6
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What is a lava tube?

A conduit—a lava tube—develops in the flow.

7
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What is the term for basalt with a glassy, ropy texture?

Pahoehoe

8
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What is the characteristic of andesitic lava flows?

They remain close to the vent.

9
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What are examples of volcaniclastic deposits?

Pyroclastic debris, preexisting rock, landslide debris

10
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What is the characteristic of a Stratovolcano (composite volcano)?

Cone-shaped with steeper slopes

11
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What type of volcano is Mauna Loa on Hawaii?

Shield volcano

12
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What is the smallest type of volcano?

Cinder cone

13
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What eruptive style is characterized by regular "burps" of magma, such as seen in Stromboli?

Strombolian eruption

14
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Which volcanic eruption style is associated with huge explosive eruptions that eject massive quantities of material?

Plinian eruption

15
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What are supervolcanoes, and where is an example located?

Large volcanic depressions with massive eruptions; Yellowstone National Park

16
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What significant event happened during the eruption of Mt. St. Helens on May 18, 1980?

The entire north side of the mountain was torn off.

17
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What is the primary gas released during volcanic eruptions?

Water (H20)

18
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How can volcanic eruptions affect climate?

By blocking sunlight with ash and aerosols

19
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Why have humans historically settled in volcanic areas despite the associated risks?

Fertile Soils

20
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What are warning signs that indicate an eruption is imminent?

Changes in shape, emission increases, earthquakes

21
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What is the primary danger associated with lava flows?

Extreme heat

22
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What is a pyroclastic flow, and why is it so destructive?

A flow of superheated ash clouds; it moves extremely fast and incinerates everything in its path.

23
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What type of volcanic material can cause roof collapses due to its weight?

Tuff

24
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In terms of volcanic hazards, what is a lateral blast?

Explosions ejected sideways

25
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What can trigger landslides during volcanic eruptions?

Earthquakes

26
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What is a lahar, and why is it so destructive?

A mudflow resulting from water mixing with ash; it can carry away everything in its path.

27
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How do volcanic eruptions contribute to the formation of earthquakes?

By moving magma

28
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What is a significant impact of volcanic eruptions on the atmosphere?

Blocking sunlight with ash and aerosols

29
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How do volcanic eruptions alter climate on a global scale?

By blocking sunlight and causing atmospheric cooling

30
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What is the purpose of danger assessment maps in volcanic areas?

To delineate danger areas for various hazards like pyroclastic flows and lahars

31
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How can eruptions be diverted, particularly lava flows?

By using explosives, heavy equipment, or seawater

32
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What is the historical significance of the eruption of Mt. Tambora in 1815?

It triggered a volcanic winter and atmospheric cooling.

33
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How do volcanoes impact human societies positively?

By providing fertile volcanic soils suitable for agriculture

34
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What is the term used to describe volcanoes that are not currently erupting but have erupted in the past 10,000 years?

Active

35
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How does volcanic activity influence the formation of lunar maria (dark "seas")?

By generating lava flows

36
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What is a shield volcano, and what type of lava does it primarily erupt?

A broad, slightly dome-shaped volcano erupting low-viscosity basaltic lava

37
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What type of volcano is Mt. St. Helens, and what style of eruption did it experience in 1980?

Composite volcano; explosive eruption

38
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What is the primary reason behind volcanic eruptions at convergent boundaries?Partial melting of the mantle

Partial melting of the mantle

39
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Where do volcanic types like shield volcanoes, cinder cones, and stratovolcanoes form in relation to tectonic settings?

Convergent boundaries

40
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What type of eruption is Stromboli known for, and how does it manifest?

Vulcanian eruption; moderate explosions every 10 to 20 minutes

41
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What volcanic phenomenon is associated with Plinian eruptions, and what is the primary characteristic of these eruptions?

Pyroclastic flows; hot ash clouds moving downslope

42
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How does volcanic activity contribute to the formation of flood basalts?

By intersecting a hot spot with a continental plate

43
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What is the characteristic feature of a caldera, and how does it form?

Gigantic volcanic depression formed by the collapse of a magma chamber

44
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What volcanic type is Mauna Loa on Hawaii an example of, and what lava type does it primarily erupt?

Shield volcano; basaltic lava

45
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What is the primary reason behind volcanic eruptions at mid-ocean ridges?

Decompressional melting

46
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How do volcanic gases, such as sulfur dioxide (SO2), contribute to eruption violence?

By reacting with water to form aerosol sulfuric acid

47
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What type of volcanic deposit is formed by pyroclastic debris that freezes in the air?

Lapilli

48
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How do lava tubes contribute to the long-distance flow of basaltic lava?

By preventing cooling, facilitating flow for miles

49
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What type of volcanic deposit is formed by pyroclastic debris that freezes in the air.

Lapilli

50
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How do lava tubes contribute to the long-distance flow of basaltic lava?

By preventing cooling, facilitating flow for miles

51
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52
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What is the primary hazard associated with lahars?

Mudflows of ash and blocks

53
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What is the primary gas emitted during volcanic eruptions, and which volcano is known for emitting this gas with a rotten-egg smell?

Sulfur dioxide (SO2); Yellowstone

54
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What volcanic feature is created when solidified lava contracts, forming hexagonal fractures?

Columnar jointing

55
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What is the primary factor that determines the flow style of lava, according to page 7?

Viscosity, dependent on composition, temperature, and gas content

56
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Which type of lava is described as having a glassy, ropy texture, and what is the Hawaiian term for it?

Pahoehoe; thin and runny

57
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What is the primary component of volcaniclastic deposits that includes frozen lava fragments?

Ignimbrite

58
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What volcanic hazard is described as an avalanche of hot ash that can move up to 300 km per hour?

Pyroclastic flow

59
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60
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Which volcanic eruption style is characterized by regular "burps" of magma, as exemplified by Stromboli?

Strombolian

61
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What type of eruption is described as moderately sized and explosive, named after an island?

Vulcanian

62
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Which volcanic eruption style is known for huge explosive events, ejecting massive quantities of material?

Plinian

63
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What is the primary gas expelled during volcanic eruptions, and which of the following does it not contribute to?

Water (H2O); lapilli formation

64
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What type of volcano is characterized by broad, slightly dome-shaped structures constructed by the lateral flow of low-viscosity basaltic lava?

Shield volcano

65
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Among the following volcanic types, which is the smallest and consists of conical piles of tephra?

Cinder Cone

66
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What volcanic hazard is characterized by mudflows resulting from water mixing with volcanic ash, and which historical event is associated with a devastating example of this hazard in Colombia?

Lahar; Nevado del Ruiz

67
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Which volcanic eruption style is associated with a plume erupting in shallow seawater, creating steam and carrying ash out of the water?

Surtseyan

68
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What is the term for the phenomenon when volcanic gases react with water to form aerosol sulfuric acid, and which eruption style is most influenced by gas escape style?

Style of gas escape; explosive eruptions

69
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Which volcanic type is characterized by alternating layers of lava, tephra, and debris, often with steeper slopes?

Stratovolcano (Composite volcano)

70
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What volcanic feature is described as a gigantic depression larger than a crater, formed when a magma chamber empties and the volcano collapses?

Caldera

71
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Which volcanic gas is the most abundant, and which one has a rotten-egg smell?

Carbon dioxide (CO2); sulfur dioxide (SO2)

72
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What volcanic feature is created when hot lava skins over, and the exterior crust cracks and breaks into fragments, especially when the lava quenches in water?

Hyaloclastite

73
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Which lava flow style is described as having a glassy, ropy texture and is associated with extremely hot basalt forming a skin that is rolled into ropy ridges and furrows?

Pahoehoe

74
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What type of lava is very hot, with low silica and low viscosity, often facilitating long-distance flow through lava tubes?

Mafic

75
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In what volcanic deposit category do lapilli, Pele's tears, Pele's hair, blocks, and bombs belong?

Tephra fall

76
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Which eruption style is described as regular "burps" of magma, and what volcanic feature is an example of this style on Stromboli Island

Strombolian; Stromboli

77
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What is the primary reason volcanic soils are highly fertile, and which ancient civilization is mentioned as an example of both prosperity and destruction due to volcanic activity?

Rich in minerals; Minoans

78
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What type of volcano is Mauna Loa on Hawaii, and what is its characteristic shape?

Shield volcano; broad and slightly dome-shaped

79
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What is the term for the average time between volcanic eruptions, and what conditions can lead to a volcano being considered "extinct"?

Extinct; not capable of erupting

80
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What is the primary reason volcanic soils are highly fertile, and which ancient civilization is mentioned as an example of both prosperity and destruction due to volcanic activity

Rich in minerals; Minoans

81
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Which volcanic architecture feature is described as a bowl-shaped depression atop a volcano, and what causes craters to form?

Crater; erupted lava piling up around the vent

82
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What is the primary difference between shield volcanoes and stratovolcanoes in terms of magma viscosity and eruption style?

Stratovolcanoes have lower viscosity and effusive eruptions.

83
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Which volcanic feature is associated with a gigantic volcanic depression, often larger than a crater, and what causes the formation of calderas?

Caldera; collapse of a volcano after a massive eruption

84
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What is the primary difference between shield volcanoes and stratovolcanoes in terms of magma viscosity and eruption style?

Shield volcanoes have lower viscosity and effusive eruptions.

85
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Which volcanic feature is associated with a gigantic volcanic depression, often larger than a crater, and what causes the formation of calderas?

Caldera; collapse of a volcano after a massive eruption

86
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What volcanic hazard involves wetted debris moving downhill, often triggered by abundant rain, and where does it typically occur?

Volcanic debris flow; on shield volcanoes

87
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What volcanic hazard is a water-rich debris flow of ash and blocks, and what is its speed and destructive potential?

Lahar; fast and extremely destructive

88
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What volcanic hazard is rarely observed due to explosions ejected sideways, and which famous eruption is an example of this hazard?

Lateral blast; Mt. St. Helens

89
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What volcanic hazard can result from the moving magma causing earthquakes, and what is the potential consequence of island arc eruptions in terms of waves?

Tsunamis; eruption of supervolcanoes

90
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How can volcanic gases, such as sulfur dioxide, impact the atmosphere, and what is the main volcanic gas released during eruptions?

Cause acid rain; sulfur dioxide

91
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What volcanic architecture feature is described as a region of flood basalts on the Moon, and what is the term for the dark "seas" on the lunar surface?

Lunar mare; dark maria

92
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What is the average time between eruptions called, and what are the stages in which volcanoes can be classified based on their activity?

Recurrence interval; erupting, dormant, extinct

93
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What warning signs can indicate an imminent eruption, and why is it challenging to predict the exact timing and style of eruptions based on these signs?

Earthquake activity, changes in shape, emission increases; unpredictability

94
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How can volcanic hazards be mitigated through planning, and what are danger assessment maps used for?

By delineating danger areas; planning and zoning

95
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In which scenario did timely evacuation save lives during a volcanic eruption, and why might evacuation efforts sometimes be met with skepticism?

Mt. St. Helens; due to a lateral blast

96
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What type of lava flow is primarily associated with basalt, and how does it affect the surrounding landscape?

Pahoehoe; ropy texture, creating ridges and furrows

97
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Describe the process of columnar jointing and the significance of this feature in volcanic geology.

Solidification of lava flows; development of hexagonal fractures

98
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What are Pele's tears and Pele's hair, and in which type of eruption are these volcanic features commonly found?

Rhyolitic eruptions; frothy volcanic glass and thin glass strands

99
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Explain the significance of ignimbrite in volcaniclastic deposits and the conditions under which it forms.

Tuff deposited while hot; welding together to form rock

100
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Examples of Accretionary Prisms

Barbados Ridge; Mediterranean Ridge; Taiwan