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133 Natural Hazards and Society > Volcanoes > Flashcards

Volcanoes Flashcards

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
Q

Hotspots

A

located in the middle of plates, hotspots of magma are gentle eruption which due to the movement of plates, form chains of islands

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26
Q

Divergent example

A

Iceland

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27
Q

Convergent example

A

cascade

28
Q

Intraplate Volcanism Oceanic Example

A

Hawaii

29
Q

Intraplate Volcanism Continental

A

Yellowstone

30
Q

Variability

A

volcanoes display a tremendous diversity in mag intensity , style and duration of eruption over days - decades

31
Q

Uncertainty

A

Variability in how an eruption might unfold

32
Q

Tephra fall

A

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
Q

1991 Pinatubo eruption

A

Ash accumilated depths of 10-15cm at airfield of 40 km South west of the P

34
Q

How many Volcanic Ash Advisory Centers are there?

A

9

35
Q

What is the prupose of the Vocalnic Ash Advisory Centers?

A

They advice the aviation industry of the location and movement of ash clouds

36
Q

What is Cristobalite?

A

A type of polymorph silica mineral forming in domes and pr prismatic crystals.

37
Q

How and where do Cristobalite form

A

Within vesicles and cracks, by vapour phase crystalisation

38
Q

What is an example of an area which this process occured

A

Chaiten, Chile ( 2008-2010)

39
Q

What is the pyroclastic density current

A

This is a fludized mixture of solid to semi -solid fragments and hot expanding gases

40
Q

How does PDC travel

A

Pyroclastic density current flows fast , hot and unpredictably down the flank of a volcanic edifice, causing the column and dome to collapse

41
Q

Speed of PDC

A

> 100km/hour

42
Q

Where are there examples of PDC in the world?

A

Soufriere Hills Volcano
Montserrat

43
Q

Why are they turbulent?

A

mixture of hot material and cold air

44
Q

Why are they valley confined

A

The dense basal flow consistsing of large block of ash

45
Q

Top?

A

Gas rich , finer grains of ash entrains the cold air wth the hot material

46
Q

What is the PDC flow

A

Dense movement made of large blovks confined in the hill

47
Q

What is a PDC surge

A

turbulent and dilute as it travels uphill

48
Q

Example of pyroclstic flow

A

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
Q

Lava flows are dependent on…

A

chemical composition ( 700-1200 degrees Celsius)
land formation ( angle/slope of land )

50
Q

What is pahoehoe lava

A

A fluid flowing form of lava with a ropey surface

51
Q

A ‘ā lava

A

Rough and jaggered form of lava

52
Q

What was the DRC 2002 event

A

Within Nyiragongo and the City of Goma , the volcano produced extreme volume of lava
Travel speed - 100 km

53
Q

How far did the lava flows reach?

A

15 km periodically as it inundated Goma

54
Q

Type of gases emmited from volcanoes?

A

CO2 carbon dioxide

SO2 sodium dioxide

H2S hydrogen sulfide

H2SO4 sulfuric acid

HCL hydrochloric acid

HF hydrogen Floride

55
Q

CO2

A

Trees killed by high carbon dioxide conc. at
Mammoth Mtn., CA

its denser than air - significant amounts accumilate on lowlands and valleys

56
Q

Example of how it affects Cameroom

A

Killing livestock from the release of CO2 from the Cameroom lakes, Nyos

57
Q

Example of how Sulfur affects Ijen, Indonesia

A
58
Q

Global effects of gases

A

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
Q

What was the 1815 Tambora event

A

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
Q

Lahars

A

Type of volcanic mudflow whereby a glacial flood outburst during raining seasons.

61
Q

What are the different types?

A

Syn-eruptive (Kelut )

Post-eruptive (Pinatubo) e.g pyroclastic flow - raining season – reactivate pyroclastic flow forming mudflows.

62
Q

What is the Nevado del ruiz event

A

1985
Eruption melted the ice cap

Ice mixed with volcanic material
- Engulfing of Armero >50 km downstream
-killing 23,000

63
Q

Who identified this hazard

A

Colombian and Italian volcanologists

64
Q

When have these events last ocuured

A

1595,1845

65
Q

Volcanic landslide and lateral blast example

A

Mount st Helens

66
Q

What happnened on 18th May 1980

A

A build up of lava increaing the pressure collapse, landslide, explsion of volcano

67
Q

What was the harbour wave Tsunami in Japan

A

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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