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133 Natural Hazards and Society > Volcanoes > Flashcards

Volcanoes Flashcards

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1
Q

Types of volcanoes

A

small monogenetic landforms and large stratovolcanoes, shield volcanoes and calderas

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2
Q

What are calderas?

A

Large explosive eruption from underlying magma chamber

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3
Q

How are calderas formed

A

The withdrawal of the underlying magma chamber causes the overlying ground to collapse underneath

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4
Q

What are monogenetic volcanoes and examples

A

small and short -term subaerial volcanoes ved by small volume of magma.

Examples include lava domes and cinder cones

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5
Q

What are strata volcanoes

A

They are a type of composite volcano, built of a plethora of layers of lava and explosive volcanic material ( years)

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6
Q

Example of calderas

A

Oregon Crater Lake

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7
Q

How are lava domes formed

A

The slow extrusion of highly-viscous silicic lava.

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8
Q

How are cinder cones formed

A

built from particles and blobs of congealed lava ejected from a single vent

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9
Q

Types of lava domes Petrographically

A

Crystal poor obsidian and crystal rich rhyolitic, basaltic andesite

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10
Q

Types of lava domes

A

Petrographically spreaking, there are crystal -poor, obsidian and crystal rich rhyolitic - basaltic andesite

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11
Q

What types of volcanic eruptions can occur

A

effusive and explosive

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12
Q

What factors are dependent on the type of volcanic eruption

A

physical properties of the erupting magma whether its viscosity or volitility

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13
Q

what are the four levels of Magmatic explosive eruptions

A

Hawaiian, Strombolian , Vulcaina , Plinian

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14
Q

Least explosive

A

Hawaiian

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15
Q

Most explosive

A

Plinian

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16
Q

Properties of Hawaiian

A

little bursts of lava flows, outwards, gentle and effusive

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17
Q

Properties of Strombolian

A

Mild blast lasting around >1hr

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18
Q

Properties of Vulcanian

A

Driven by gas locked within the volcano

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19
Q

Properties of Plinian

A

Most powerful explosions, sustained, and continuous lasting for days

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20
Q

What are Phreatomagmatic

A

Explosive eruptions with groundwater interaction
generating an increased explosivity

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21
Q

What is the VEI stand for?

A

Volcanic Explosivity Index measuring the magnitude to frequency relationship

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22
Q

Different type of parameters

A

volume of tephra
Cloud column and height in km
qualitative descriptions
eruption types
duration
CAVW max explosivity
Tropospheric interjection

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23
Q

What is the distribution of active volcanoes

A

Linked to the plate tectonics ( and its few annomalies)
Majority are along the plate margin

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24
Q

Plate margin examples

A

Divergent , convergent

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25
Hotspots
located in the middle of plates, hotspots of magma are gentle eruption which due to the movement of plates, form chains of islands
26
Divergent example
Iceland
27
Convergent example
cascade
28
Intraplate Volcanism Oceanic Example
Hawaii
29
Intraplate Volcanism Continental
Yellowstone
30
Variability
volcanoes display a tremendous diversity in mag intensity , style and duration of eruption over days - decades
31
Uncertainty
Variability in how an eruption might unfold
32
Tephra fall
As the material produced from an explotion reached up towards the surface, pressure increases causing fragmentation from the surface region to froth and through the volcanuc plume, material explodes up and outwards
33
1991 Pinatubo eruption
Ash accumilated depths of 10-15cm at airfield of 40 km South west of the P
34
How many Volcanic Ash Advisory Centers are there?
9
35
What is the prupose of the Vocalnic Ash Advisory Centers?
They advice the aviation industry of the location and movement of ash clouds
36
What is Cristobalite?
A type of polymorph silica mineral forming in domes and pr prismatic crystals.
37
How and where do Cristobalite form
Within vesicles and cracks, by vapour phase crystalisation
38
What is an example of an area which this process occured
Chaiten, Chile ( 2008-2010)
39
What is the pyroclastic density current
This is a fludized mixture of solid to semi -solid fragments and hot expanding gases
40
How does PDC travel
Pyroclastic density current flows fast , hot and unpredictably down the flank of a volcanic edifice, causing the column and dome to collapse
41
Speed of PDC
>100km/hour
42
Where are there examples of PDC in the world?
Soufriere Hills Volcano Montserrat
43
Why are they turbulent?
mixture of hot material and cold air
44
Why are they valley confined
The dense basal flow consistsing of large block of ash
45
Top?
Gas rich , finer grains of ash entrains the cold air wth the hot material
46
What is the PDC flow
Dense movement made of large blovks confined in the hill
47
What is a PDC surge
turbulent and dilute as it travels uphill
48
Example of pyroclstic flow
Mount Pelee 1902 - peak of volcano explosion at the peak of the volcano, both pyroclastic flow and surges occured 28,00 residents 3 survivors
49
Lava flows are dependent on...
chemical composition ( 700-1200 degrees Celsius) land formation ( angle/slope of land )
50
What is pahoehoe lava
A fluid flowing form of lava with a ropey surface
51
A ‘ā lava
Rough and jaggered form of lava
52
What was the DRC 2002 event
Within Nyiragongo and the City of Goma , the volcano produced extreme volume of lava Travel speed - 100 km
53
How far did the lava flows reach?
15 km periodically as it inundated Goma
54
Type of gases emmited from volcanoes?
CO2 carbon dioxide SO2 sodium dioxide H2S hydrogen sulfide H2SO4 sulfuric acid HCL hydrochloric acid HF hydrogen Floride
55
CO2
Trees killed by high carbon dioxide conc. at Mammoth Mtn., CA its denser than air - significant amounts accumilate on lowlands and valleys
56
Example of how it affects Cameroom
Killing livestock from the release of CO2 from the Cameroom lakes, Nyos
57
Example of how Sulfur affects Ijen, Indonesia
58
Global effects of gases
Sulfate Areosoles can form from the interaction between sulfur, co2 and atmosphere can absorb IR by aerosols backscatter from aerosols ash particles in the stratosphere
59
What was the 1815 Tambora event
The summer of 1815, Tambora eruption occured but the global effects were only felt in the following year Global cooling, most prevalent in Europe causing sig number of deaths
60
Lahars
Type of volcanic mudflow whereby a glacial flood outburst during raining seasons.
61
What are the different types?
Syn-eruptive (Kelut ) Post-eruptive (Pinatubo) e.g pyroclastic flow - raining season – reactivate pyroclastic flow forming mudflows.
62
What is the Nevado del ruiz event
1985 Eruption melted the ice cap Ice mixed with volcanic material - Engulfing of Armero >50 km downstream -killing 23,000
63
Who identified this hazard
Colombian and Italian volcanologists
64
When have these events last ocuured
1595,1845
65
Volcanic landslide and lateral blast example
Mount st Helens
66
What happnened on 18th May 1980
A build up of lava increaing the pressure collapse, landslide, explsion of volcano
67
What was the harbour wave Tsunami in Japan
A volcanic eruption occuing underneath the sea, by the ocean Hitting land reaches up to 40 meters high Subsequent tsunami in Hilo Hawaii on 1 April 1946

133 Natural Hazards and Society (10 decks)

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