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GEOLOGY 101 > CH. 5: Volcanoes & Volcanic Hazards > Flashcards

CH. 5: Volcanoes & Volcanic Hazards Flashcards

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1
Q

Effusive volcanoes are those with low viscosity lavas that are likely ____ in composition. A _____ volcano is usually effusive.

A

mafic / shield

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2
Q

The character of a lava flow depends on the viscosity of the lava erupted. _____ lava is less viscous than ____ lava.

A

basaltic / rhyolitic

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3
Q

Which of the following terms best describes this extrusive igneous feature?

A

pahoehoe lava

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4
Q

rhyolite lava:

A

tends to erupt explosively due to pressure buildup from the high viscosity of the lava

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5
Q

volatile rich magmas are generated by melting due to addition of volatiles. At what plate tectonic setting does this occur?

A

convergent subduction

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6
Q

A caldera forms by:

A

draining of a magma chamber beneath a volcano during an eruption

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7
Q

Which of these volcanic settings produced 70% of the Earth’s surface?

A

lavas erupted at mid-ocean ridges

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8
Q

Which of the following is false about hot spot volcanism?

A

hot spot volcanoes are always explosive

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9
Q

Mt. Vesuvius erupted in a very violent explosion in 79 CE and buried the residents of Pompeii in ash. On the basis on this information, which of the following would you LEAST expect to find at Vesuvius?

A

basaltic (mafic) lava

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10
Q

Which of the following is true about lahars:

A

all are true about lahars

can occur even if an eruption has not occurred recently

can carry away people/buildings/other structures

high density + fast flowing floods of water and tephra

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11
Q

What makes CO2 gas hazardous to humans?

A

all are true about CO2 gas

it is colorless and odorless

it is denser than air so it will not rise rapidly and can easily be breathed i without one’s knowledge of its presence

it can deprive the brain of oxygen and cause fainting and or death

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12
Q

Flood basalts typically originate from:

A

a mantle plume

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13
Q

In the Mastering Geology assignment this week we learned about Flood Basalts. One example was the Columbia River Flood Basalt Province. Which of the following are true about these flood basalts?

A

the relatively flat features of solidified flood basalts is indicative of the very low viscosity of the lava when it was erupted and emplaced

the flood basalts have fine grained texture that indicates relative fast extrusive cooling

thick layers of basalt indicate many repeated eruptions of multiple lava flows with the youngest flows at the top

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14
Q

True or False. Landslides can cause volcanic eruptions even in extinct volcanoes

A

False

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15
Q

Identify the FALSE statement about pyroclastic flow hazards

A

they can flow up to 100 km away from a volcano

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16
Q

Why are volcanic rocks often exposed at Earth’s surface as hills, ridges, and mountains surrounded by areas of lower elevation?

A

volcanic rocks are often more resistant to erosion than surrounding rock

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17
Q

What main hazard do lava flows pose to humans?

A

destruction of immovable property

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18
Q

The main difference between lavas that form pahoehoe texture and lavas that form aa texture is:

A

temperature

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19
Q

The volcanic islands in the above figure were created as the tectonic plate passed over a hot spot in the mantle. Based on the ages of the volcanic islands, in what direction was the tectonic plate moving toward?

A

west

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20
Q

In which of the following lava types would you expect to see the development of pahoehoe?

A

basalt

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21
Q

Continental rifts produce magma that is formed by ____ melting in the mantle with felsic magmas produced by _____

A

decompression / partial melting of continental crust

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22
Q

If you find a 500 meter depression atop a volcano, it is likely a:

A

crater

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23
Q

Match each of the following ocean features with their tectonic setting.

  1. seamounts
  2. island arcs
  3. mid ocean ridge
A
  1. hot spots
  2. subduction zone
  3. divergent plate boundary
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24
Q

Identify the FALSE statement about volcanic ash hazards

A

it is not hazardous if breathed in because the size of particles is too small

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25
Q

Are rhyolite eruptions always explosive?

A

no, sometimes they produce lava domes that erupt very slowly over many years

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26
Q

What is the smallest size classification of pyroclastic material?

A

ash

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27
Q

Based on the following definitions, match the correct state of a volcano.

  1. ____ volcanoes are those that are currently erupting
  2. ____ volcanoes are those that aren’t capable of erupting
  3. ____ volcanoes are those that have recently erupted
  4. ____ volcanoes are those that have not erupted in hundreds of thousands of years
A
  1. active
  2. extinct
  3. active
  4. dormant
28
Q

Considering a mafic melt, define the following magma properties as compared to a felsic melt.

  1. silica content
  2. viscosity
  3. tendency to produce pyroclastic material
  4. eruptive temperature
A
  1. lower
  2. lower
  3. lower
  4. higher
29
Q

What are the two primary factors that determine the manner in which magma erupts?

A

Viscosity of magma and the amount of gasses in magma. An increasing in either or both of those factors makes eruption more explosive.

30
Q

explosive eruption

A

volcano fed by silica rich magma

31
Q

nonexplosive eruption

A

volcano fed by magma with low of dissolved gases

volcano fed by mafic (basaltic) magma

volcano fed by high temperature (100 degree Celsius) magma`

32
Q

not related to eruption explosiveness

A

volcano that has not erupted for a long time

volcano at high elevation

33
Q

Why are shield volcanoes wider than composite volcanoes?

A

The lava that flows out of shield volcanoes is more fluid than the lava that flows out of composite volcanoes.

34
Q

A ____ has broad and moderately steep flanks and a steep summit. It results from the eruption of a mixture of both lava flows and pyroclastic deposits that contain less fluid materials and travel shorter distances.

A

composite volcano

35
Q

A wide volcano that produces mainly basaltic lava flows is called a _____

A

shield volcano

36
Q

A very steep-sided volcano built primarily from ejected lava fragments is called a ____

A

cinder cone

37
Q

Broad sheets of fluid ____ lava travel long distances and give shield volcanoes their distinctive shape.

A

basaltic

38
Q

Moderately viscous and gas-rich ____ lavas can erupt as lava flows or pyroclastic materials, leading to the steepening slope of composite volcanoes.

A

andesitic

39
Q

Explosive eruptions of ____ create steep-sided cinder cone volcanoes.

A

pyroclastic materials

40
Q

cinder cone

A

volcano known for reddish brown lapilli

volcano with a crater at the summit and steep flanks

41
Q

shield volcano

A

volcano with very broad slopes and a caldera

volcano known for long lava flows and lava tubes

42
Q

composite cone

A

volcano with a steep summit and broad moderately steep flanks

volcano known for erupting lava and pyroclastic material

43
Q

Which of the following types of magma has the highest viscosity?

A

rhyolitic

44
Q

In addition to viscosity, which of the following parameters has an influence on whether a volcanic eruption will be effusive or violent?

A

amount of gas in the magma

45
Q

Which of the following types of lava will most likely lead to a volcanic eruption of an effusive nature?

A

basaltic

46
Q

Which volcanoes are sometimes very large, with a gently sloping mound composed mainly of lava flows?

A

Shield

47
Q

To what is the geologically recent volcanic activity in Yellowstone National Park usually attributed?

A

Yellowstone volcanism is usually attributed to intraplate (meaning “within the plate”), hot spot volcanism.

48
Q

Of the following choices, which best describes Mt. St. Helens?

A

An explosive stratovolcano

49
Q

Which type of basaltic lava flow has its surface covered with sharp-edged, angular blocks and rubble?

A

A’a

50
Q

Why would a plume of solid silicate rock rising slowly from deep in the mantle begin melting as it neared the base of the lithosphere?

A

Melting temperatures drop because the pressure is lowered.

51
Q

Which one of the following best describes volcanism of the Cascade Range in the northwestern United States?

A

The volcanism is related to plate subduction.

52
Q

What type of magma is the most abundant at oceanic-spreading centers?

A

Basaltic

53
Q

__________ destroyed the city of St. Pierre, Martinique in 1902.

A

Nueé ardente

54
Q

Which type of basaltic lava flow has a fairly smooth, unfragmented, ropy surface?

A

Pahoehoe

55
Q

What type of magma typically comprises stratovolcanoes?

A

Andesitic

56
Q

Which one of the following statements concerning volcanic blocks and bombs is true?

A

Blocks are ejected as solid fragments; bombs are ejected as magma lumps.

57
Q

What is the most common volatile constituent in both magmas and volcanic gases?

A

Water

58
Q

What fate befell the “Lost City of Atlantis” mentioned in Plato’s writings?

A

It disappeared as part of caldera collapse following a major, explosive, volcanic eruption.

59
Q

Which of the following statements best describes the Hawaiian volcanoes?

A

The Hawaiian volcanoes are situated in the interior of a Pacific plate above a hot spot deep in the mantle.

60
Q

What is the largest known volcano in the solar system?

A

Olympus Mons, Mars

61
Q

What volcanic events formed Crater Lake, Oregon? When did they take place?

A

Caldera collapse followed by major ash and pyroclastic-flow eruptions; 7000 years ago.

62
Q

What two gases are the most abundant gases emitted during basaltic volcanism?

A

Water and carbon dioxide

63
Q

Which kind of volcanism is typical of mid-oceanic ridge systems?

A

Submarine; basaltic lava flows

64
Q

Which one of the following shows the correct order from left to right of decreasing magmatic viscosity?

A

Rhyolite, andesite, basalt

65
Q

Which region has the greatest concentration of currently active volcanoes?

A

The circum-Pacific area or “Ring of Fire”

66
Q

Which ocean basin is rimmed by the most subduction zones?

A

Pacific

67
Q

What type of volcanoes are Kilauea and Mauna Loa in Hawaii?

A

Basaltic shield volcanoes

GEOLOGY 101 (5 decks)

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