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GEO 101 > volcanoes (5) > Flashcards

volcanoes (5) Flashcards

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1
Q

Compare the 1980 eruption of Mt. St. Helens to a typical eruption of Hawaii’s Kilauea Volcano.

A

Mt. St. Helens- massive eruption with death and destruction

Kilauea- magma slowly seeps out and isn’t that dangerous

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2
Q

Magma

A

A molten rock found at depth, including any dissolved gases and crystals

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3
Q

Lava

A

Magma that reaches Earth’s surface

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4
Q

Effusive Eruption

A

A quiescent eruption that produces mainly outpourings of fluid lava

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5
Q

Viscosity

A

A measure of fluid’s resistance to flow

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6
Q

The more silica present in magma, the _____ its viscosity

A

Greater

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7
Q

Eruption Column

A

Buoyant plumes of hot, ash-laden gases that can extend thousands of meters into the atmosphere

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8
Q

List these magmas in order from highest to lowest silica content:
mafic (basaltic) magma
felsic (granitic/rhyolitic) magma
intermediate (andesitic) magma

A

Felsic
Intermediate
Mafic

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9
Q

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

A

Viscosity

Gas content

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10
Q

Are volcanoes fed by highly viscous magma more or less likely to be a greater threat to life and property than volcanoes supplied with very fluid magma?

A

Highly viscous magma is a greater threat

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11
Q

Aa Flow

A

A type of lava flow that has a jagged, blocky surface

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12
Q

Pahoehoe Flow

A

A lava flow with a smooth to ropy surface

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13
Q

Lava Tube

A

A tunnel in hardened lava that acts as horizontal conduit for lava flowing from a volcanic vent. Lava tubes allow fluid lavas to advance great distances

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14
Q

Block Lava

A

Lava that has a surface of angular blocks associated with material having andesitic and rhyolitic compositions

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15
Q

Pillow Lava

A

Basaltic lava that solidifies in an underwater environment and develops a structure that resembles a pile of pillows

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16
Q

Volatiles

A

Gaseous components of magma dissolved in the melt. Volatiles will readily vaporize (form a gas) at surface pressures

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17
Q

Pyroclastic Material

A

The volcanic rock ejected during an eruption. Pyroclastic include ash, bombs, and blocks

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18
Q

Contrast pahoehoe and aa lava flows.

A

Pahoehoe are more rapid, lower viscosity and rope-like

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19
Q

List the main gases released during a volcanic eruption.

A 
Water vapor
Carbon Dioxide
Carbon Monoxide
Sulfer Dioxide
Hydrogen Sulfide
Nitrogen
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20
Q

How do volcanic bombs differ from blocks of pyroclastic debris?

A

Bombs leave the volcano as liquids

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21
Q

What is scoria? How is it different from pumice?

A

Vesicular rock with a basaltic composition

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22
Q

Fissure

A

A crack in rock along which there is a distinct separation

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23
Q

Conduit

A

A pipeline opening through which magma moves toward Earth’s surface. It terminates at a surface opening called a vent

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24
Q

Vent

A

The surface opening of a conduit or pipe

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25
Q

Volcanic Cone

A

A cone-shaped structure built by successive eruptions of lava and/or pyroclastic materials

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26
Q

Crater

A

The depression at the summit of a volcano or a depression that is produced by a meteorite impact

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27
Q

Caldera

A

A large depression typically caused by collapse or ejection of the summit area of a volcano

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28
Q

Parasitic Cone

A

A volcanic cone that forms on the flank of a larger volcano

29
Q

Fumarole

A

A vent in a volcanic area from which fumes or gases escape

30
Q

Shield Volcano

A

A broad, gently sloping volcano built from fluid basaltic lavas

31
Q

Seamount

A

An isolated volcanic peak that rises at least 1000 meters above the deep-ocean floor

32
Q

Describe the composition and viscosity of the lava associated with shield volcanoes.

A

Mafic, low viscosity (ooz out)

33
Q

Are pyroclastic materials a significant component of shield volcanoes?

A

No, they only make up a few percent

34
Q

Where do most shield volcanoes form-on the ocean floor or on the continents?

A

On the ocean floor

35
Q

Cinder cone

A

A rather small volcano built primarily of ejected lava fragments that consist mostly of pea-to-walnut-size lapilli

36
Q

Describe the composition of a cinder cone.

A

Pyroclastic, mafic, scoria is formed, sometimes a lava flow from the base

37
Q

How do cinder cones compare with shield volcanoes in terms of size and the steepness of their flanks?

A

Cinder cones are much smaller and much steeper

38
Q

Composite Volcano/Stratovolcano

A

A volcano composed of both lava flows and pyroclastic material

39
Q

What is the name given to the region having the greatest composite volcanoes?

A

Ring of Fire

40
Q

Describe the materials that compose composite volcanoes.

A

Pyroclastic material and lava flows

41
Q

How do the composition and viscosity of lava flows differ between composite volcanoes and shield volcanoes?

A

Composite volcanoes have silica rich intermediate magma

Shield volcanoes tend to be basalt only (less variety than composite)

42
Q

Pyroclastic Flow

A

A highly heated mixture, largely of ash and pumice fragments, that travel down the flanks of a volcano or along the surface of the ground

43
Q

Nuee Ardente

A

Incandescent volcanic debris buoyed up by hot gases that moves downslope in an avalanche fashion

44
Q

Lahar

A

A debris flow on the slopes of a volcano that results when unstable layers of ash and debris become saturated and flow downslope, usually following stream channels

45
Q

Tsunamis

A

The Japanese word for seismic sea wave

46
Q

Why are pyroclastic flows capable of traveling great distances?

A

Gases reduce friction

47
Q

List 3 volcanic hazards besides pyroclastic flows and lahars

A

Tsunami
Aviation risk from ash
Respiratory health

48
Q

Fissure Eruption

A

An eruption in which lava is extruded from narrow fractures or cracks in the crust

49
Q

Basalt Plateau

A

The broad and extensive accumulation of lava from a succession of flows emanating from fissure eruptions

50
Q

Flood Basalts

A

Flows of basaltic lava that issue from numerous cracks or fissures and commonly cover extensive areas to thicknesses of hundreds of meters

51
Q

Lava Dome

A

A bulbous mass associated with an old-age volcano, produced when thick lava is slowly squeezed from the vent. Lava domes may act as plugs to deflect subsequent gaseous eruptions

52
Q

Volcanic Neck/Plug

A

An isolated steep-sided, erosional remnant consisting of lava that once occupied the vent of a volcano

53
Q

Describe the formation of Crater Lake.

A

Mt. Mazama was erupting explosively that emptied out the magma that was feeding the volcano, the volcano collapsed, rain filled it

54
Q

How do the eruptions that created the Columbia Plateau differ from the eruptions that create large composite volcanoes?

A

The Columbia Plateau was created by fissure eruptions (flood basalts) low viscosity

55
Q

What type of volcanic structure is Shiprock, New Mexico, and how did it form?

A

Volcanic neck

56
Q

Ring of Fire

A

The zone of active volcanoes surrounding the Pacific Ocean

57
Q

Volcanic Island Arc

A

A chain of volcanic islands generally located a few hundred kilometers from a trench where there is active subduction of one oceanic plate beneath another

58
Q

Continental Volcanic Arc

A

Mountains formed in part by igneous activity associated with the subduction of oceanic lithosphere beneath a continent. Examples include the Andes and the Cascades

59
Q

Intraplate Volcanism

A

Igneous activity that occurs within a tectonic plate, away from plate boundaries

60
Q

Mantle Plume

A

A mass of hotter-than-typical mantle material that ascends toward the surface, where it may lead to igneous activity. These plumes of solid yet mobile material may originate as deep as the core-mantle boundary

61
Q

Hot Spot

A

A concentration of heat in the mantle, capable of producing magma that, in turn, extrudes onto Earth’s surface. The intraplate volcanism that produced the Hawaiian Islands is one example.

62
Q

Superplume

A

A large area of the mantle that is dominated by the upwelling of hot mantle rock, which originates near the mantle-core boundary

63
Q

Are volcanoes in the Ring of Fire generally described as effusive or explosive?

A

Explosive

Ex: Mt. St. Helens

64
Q

How is magma generated along convergent plate boundaries?

A

Subduction zones; hydrated minerals release water to surrounding mantle which lowers the temperature melting point MAFIC MAGMA

65
Q

Volcanism at divergent plate boundaries is most often associated with which magma type?

A

Mafic (iron and magnesium)

66
Q

What is thought to be the source of magma for most intraplate volcanism?

A

Plumes, hot spots, rising material

67
Q

What three factors do volcanologists monitor in order to determine whether magma is migrating toward Earth’s surface?

A

Changes in Earthquake patterns
Change in size
Change in inflation of cone
Change in gases

68
Q

What volcanic hazard does the warning system installed around Mount Rainier aim to identify?

A

Lahars

GEO 101 (19 decks)

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