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Geology 102 > Volcanoes > Flashcards

Volcanoes Flashcards

1
Q

The pacific ______ ___ _____ is a belt of volcanism that surrounds the pacific

A

ring of fire

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2
Q

Where in north america is popular for its volcanoes

A

Yellowstone hot spot
Cascade mountains

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3
Q

What is pyroclastic material

A

solid rock fragments ejected during an eruption

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4
Q

Define a volcano

A

a vent from which magma, gases and solids are ejected, pyroclastic
materials and lava flows can build up to form a mountain-like shape

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5
Q

Define eruption

A

the process of magma and pyroclastic materials being ejected
from a volcano

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6
Q

Define Tephra

A

Air-borne pyroclastic material. Tephra varies in size:
the largest are bombs, lapilli (gravel size), ash (finest size).

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7
Q

_______ composition is an important factor determining the shape of a volcano and its style of eruption

A

Magma

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8
Q

magma composition determines

A

mineralogy - and thus melting
temperature
* how well it traps gasses
influences melting
temperature and
explosiveness

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9
Q

______ polymers are c0ntained in magma

A

silica

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10
Q

how much silica is in mafic rocks and what is the temperature

A

50%
1200+oC

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11
Q

how much silica is in intermediate rocks and what is the temperature

A

60%
1000+oC

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12
Q

how much silica is in Felsic rocks and what is the temperature

A

70%
800+
o
C

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13
Q

Where do we find mafic rocks

A

hot spots and divergent plate margins

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14
Q

Where do we find intermediate rocks

A

source ocean-ocean or ocean-continent convergent
plate margins

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15
Q

Where do we find felsic rocks

A

ocean
continent plate margins
or continental hot spots

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16
Q

List the following from most mafic to most felsic: Pyroxene, amphibole, mice, Olivine, quartz, biotite

A

Olivine, Pyroxene, amphibole, biotite mice, quartz

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17
Q

Low silica content results in what viscosity

A

basalt very low viscosity

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18
Q

High silica content results in what viscosity

A

More felsic mineral, high viscosity

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19
Q

High volatile content results in what viscosity

A

Decrease viscosity

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20
Q

Higher temperature results in what viscosity

A

Low viscosity

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21
Q

Lower temperature results in what viscosity

A

higher viscosity

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22
Q

define Pahoehoe

A

basaltic flow of lower viscosity (more fluid),
ropy structure

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23
Q

define Aa lava

A

sharp, spiny, surface, basaltic deposit of higher
viscosity (less fluid)

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24
Q

Basaltic lava has ____ viscosity and can flow _____ distances

A

low
long

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25
Q

Andesitic lava is too viscous to flow far, and tends to ____ ____ as it flows

A

break up

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26
Q

Felsic lava is so viscous that is may _____ ____ in a dome-shaped mass

A

pile up

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27
Q

All magmas contain small amounts of dissolved gas. What is the range

A

0.2 - 6%

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28
Q

What are the most common dissolved gases in magma

A

water vapor and CO2

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29
Q

What is an important volatile to remember is not contained in magma

A

O2

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30
Q

How do volatiles affect magma

A
  • Breaking up silica polymers, makes magma less viscous
  • Generating bubbles of gas – makes magma bubbly
  • If the magma is high in silica (felsic), the silica polymers
    trap the bubbles, and it is more explosive!
31
Q

Mafic magma tends to have _____ volatile content

A

low

32
Q

Felsic magma tends to have ______ volatile content

A

higher

33
Q

How do volatiles change the characteristics of felsic magma

A

decreases melting temperature
decreases viscosity

34
Q

Does mafic magma or felsic magma have a greater tendency to form pyroclastic

A

Felsic magma

35
Q

Types of intrusions in intrusive volcanic landforms

A

sill, dike, veins

36
Q

Types of conduits in intrusive volcanic landforms

A

pipe, vent, neck

37
Q

Types of magma chambers in intrusive volcanic landforms

A

Laccolith, stock, batholith/plutons

38
Q

What are the volcano shapes and types

A

*Shield volcano
*Cinder cone
*Stratovolcano
*Flood basalts
*Caldera volcano
*Mid ocean ridges

39
Q

Describe shield volcanoes

A

The largest conical volcanoes
Formed from basalt
Gentle slopes
Lava flows quickly and over great distances.

40
Q

Describe cinder cones

A

Small volcano, only 100m in diameter
slope angle is 24-32o
Often form on the side of shield volcanoes
Built of pyroclastic material
mostly mafic

41
Q

Describe composite cones(stratovolcanoes)

A

Intermediate in size and average composition
Variable slope angle but often have a conical shape
Located along subduction zones

42
Q

Describe stratovolcanoes and eruptive style

A

dangerous
Generate plinian eruptions, eject huge amounts of ash, column extending to the stratosphere and distributed over large regions

43
Q

For a stratovolcano the deposits alternate between _________ lava flow and __________ deposits

A

andesitic
pyroclastic

44
Q

Describe a flood basalt

A
  • Basaltic lava flow, very fluid, ejected from a
    fissure (crack) and flooding a large area
  • Fed from mantle plumes
    *Creates lava plateau
45
Q

What does the Giants causeway have that makes it so cool. What type of volcano is is

A

Columnar joints
Flood basalt

46
Q

Describe a caldera volcano

A

*A volcanic crater that develops
from the explosion and
collapse of a composite
volcano.
violent and infrequent

47
Q

What are some examples of caldera volcanoes

A

Crater lake
Krakatoa, Indonesia (generated a tsunami that made it to Europe)

48
Q

What is the most explosive type of volcano

A

Rhyolite caldera complexes

49
Q

What are some examples of rhyolite caldera volcanoes

A

Yellowstone
Taupo

50
Q

Why do the slides say that yellowstone is breathing

A

cycle of uplift and
subsidence at Yellowstone
* Caused by movement of magma and/or fluids (hot water
and gases) underneath the caldera
there is more earthqaukes and vertical deformation

51
Q

Do mid ocean ridge eathqaukes effect humans

A

Not really because they are so remote

52
Q

Define lava domes

A

lava too viscous to flow and piles
up at vent. Cools quickly generating glassy
high silica obsidians.

53
Q

Define spatter cones

A

very small basaltic cones, build
up around vents where magma is splattered by
bubbles of gasses

54
Q

Define volcanic plugs or volcanic necks

A

lava cools and plugs
the vent.

55
Q

What are volcanic hazards

A

eruption column, debris avalanche, pyroclastic flow, fumaroles, lava, dome collapse, bombs, acid rain

56
Q

Where was there an eruptive blast and earthquake from a volcano exploding that caused a bunch of trees to drop down

A

Mt. St. Helens

57
Q

What problems can arise due to ash from volcanoes

A

The ash reflects the suns light and can decrease the global temperature
it is an abrasive - irritant to eyes and lungs
weighs a lot on your roof
hazardous for engines, especially planes
Destruction of vegetation

58
Q

What is the benefit of ash

A

Creates fertile soils after
weathering!

59
Q

Define fumarole

A

vents that emit hot gases, can be
1000ºC.

60
Q

Why are Gases problematic in relation to the ones emitted from volcanos

A

Gases such a CO
2
and H
S are invisible,
but can asphyxiate or poison people.
2
Gasses can also dissolve in water droplets in the
air and lead to acid rain

61
Q

What does Nuee ardente mean

A

glowing cloud - gas cloud that is very hot and turbulent

62
Q

How large are bombs

A

pyroclasts
that are >32 mm in
size

63
Q

What does lahar mean

A

volcanic debris flow (hot
mud flow)
* a particular hazard when
volcanoes are ice/snow
capped

64
Q

When lava flow occurs, is it more likely that life is lost, or loss of property and vegetation

A

loss of property and vegetation is more common

65
Q

What are phreatic explosions

A
  • Occur when magma comes in contact with water or ice
  • Occurs in subterranean volcanoes or island arc volcanoes
  • involve the contact of magma and water during the eruption
  • Explosive!
66
Q

long term prediction vs short term prediction

A

Long term predictions
Identify potential areas of volcanic activity
Short term prediction
Can be very useful, especially in evacuating
personnel.

67
Q

What is the difference between a non-explosive and explosive volcano

A

non-explosive means that is is not too dangerous, there is low viscosity magma and low amount of dissolved gas
Explosive means the viscosity of the magma is high and the dissolved gas content is high

68
Q

What does VEI stand for

A

Volcanic explosion index

69
Q

What is the VEI good for

A

VEI ratings are on a 0-8 scale,
and represent the explosive
tendency of an eruption

  • It is based on volume of
    ejected material, height of
    ejected material and duration
    of eruption
70
Q

What type of boundary would we find a stratovolcano?

A

Convergent, specifically a subduction zone

71
Q

What type of boundary would we find a shield volcano

A

Not at a boundary, it is at a hotspot

72
Q

What type of boundary would we find sea-floor volcanism

A

divergent

73
Q

Where would we expect to see a volcanic plumes/ hot spot volcanoes occur

A

Hawaii
Yellowstone (caldera containing granitic/rhyolitic magma which makes it highly explosive)

Geology 102 (11 decks)

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