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Geology 102 > Volcanoes > Flashcards

Volcanoes Flashcards

(73 cards)

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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
Andesitic lava is too viscous to flow far, and tends to ____ ____ as it flows
break up
26
Felsic lava is so viscous that is may _____ ____ in a dome-shaped mass
pile up
27
All magmas contain small amounts of dissolved gas. What is the range
0.2 - 6%
28
What are the most common dissolved gases in magma
water vapor and CO2
29
What is an important volatile to remember is not contained in magma
O2
30
How do volatiles affect magma
* 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
Mafic magma tends to have _____ volatile content
low
32
Felsic magma tends to have ______ volatile content
higher
33
How do volatiles change the characteristics of felsic magma
decreases melting temperature decreases viscosity
34
Does mafic magma or felsic magma have a greater tendency to form pyroclastic
Felsic magma
35
Types of intrusions in intrusive volcanic landforms
sill, dike, veins
36
Types of conduits in intrusive volcanic landforms
pipe, vent, neck
37
Types of magma chambers in intrusive volcanic landforms
Laccolith, stock, batholith/plutons
38
What are the volcano shapes and types
*Shield volcano *Cinder cone *Stratovolcano *Flood basalts *Caldera volcano *Mid ocean ridges
39
Describe shield volcanoes
The largest conical volcanoes Formed from basalt Gentle slopes Lava flows quickly and over great distances.
40
Describe cinder cones
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
Describe composite cones(stratovolcanoes)
Intermediate in size and average composition Variable slope angle but often have a conical shape Located along subduction zones
42
Describe stratovolcanoes and eruptive style
dangerous Generate plinian eruptions, eject huge amounts of ash, column extending to the stratosphere and distributed over large regions
43
For a stratovolcano the deposits alternate between _________ lava flow and __________ deposits
andesitic pyroclastic
44
Describe a flood basalt
* Basaltic lava flow, very fluid, ejected from a fissure (crack) and flooding a large area * Fed from mantle plumes *Creates lava plateau
45
What does the Giants causeway have that makes it so cool. What type of volcano is is
Columnar joints Flood basalt
46
Describe a caldera volcano
*A volcanic crater that develops from the explosion and collapse of a composite volcano. violent and infrequent
47
What are some examples of caldera volcanoes
Crater lake Krakatoa, Indonesia (generated a tsunami that made it to Europe)
48
What is the most explosive type of volcano
Rhyolite caldera complexes
49
What are some examples of rhyolite caldera volcanoes
Yellowstone Taupo
50
Why do the slides say that yellowstone is breathing
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
Do mid ocean ridge eathqaukes effect humans
Not really because they are so remote
52
Define lava domes
lava too viscous to flow and piles up at vent. Cools quickly generating glassy high silica obsidians.
53
Define spatter cones
very small basaltic cones, build up around vents where magma is splattered by bubbles of gasses
54
Define volcanic plugs or volcanic necks
lava cools and plugs the vent.
55
What are volcanic hazards
eruption column, debris avalanche, pyroclastic flow, fumaroles, lava, dome collapse, bombs, acid rain
56
Where was there an eruptive blast and earthquake from a volcano exploding that caused a bunch of trees to drop down
Mt. St. Helens
57
What problems can arise due to ash from volcanoes
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
What is the benefit of ash
Creates fertile soils after weathering!
59
Define fumarole
vents that emit hot gases, can be 1000ºC.
60
Why are Gases problematic in relation to the ones emitted from volcanos
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
What does Nuee ardente mean
glowing cloud - gas cloud that is very hot and turbulent
62
How large are bombs
pyroclasts that are >32 mm in size
63
What does lahar mean
volcanic debris flow (hot mud flow) * a particular hazard when volcanoes are ice/snow capped
64
When lava flow occurs, is it more likely that life is lost, or loss of property and vegetation
loss of property and vegetation is more common
65
What are phreatic explosions
* 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
long term prediction vs short term prediction
Long term predictions Identify potential areas of volcanic activity Short term prediction Can be very useful, especially in evacuating personnel.
67
What is the difference between a non-explosive and explosive volcano
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
What does VEI stand for
Volcanic explosion index
69
What is the VEI good for
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
What type of boundary would we find a stratovolcano?
Convergent, specifically a subduction zone
71
What type of boundary would we find a shield volcano
Not at a boundary, it is at a hotspot
72
What type of boundary would we find sea-floor volcanism
divergent
73
Where would we expect to see a volcanic plumes/ hot spot volcanoes occur
Hawaii Yellowstone (caldera containing granitic/rhyolitic magma which makes it highly explosive)

Geology 102 (11 decks)

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