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Hazards > Volcanoes > Flashcards

Volcanoes Flashcards

1
Q

What type of slope does a shield volcano have?

A

Gentle slopes built from previous eruptions.

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2
Q

What type of lava is released by shield volcanoes?

A

Runny lava

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3
Q

How often do shield volcanoes erupt?

A

Frequent eruptions

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4
Q

Are shield volcano eruptions mild or severe?

A

Mild

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5
Q

What are the slopes of composite volcanoes like?

A

They have steep sides.

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6
Q

What type of volcano can be found at hotspots?

A

Shield

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7
Q

How are seamounts formed?

A

Extinct volcanoes apply too much pressure on the crust so subsidence occurs. This, combined with erosion creates sea mounts.

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8
Q

What type of volcano is found at subduction zones?

A

Composite

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9
Q

What type of volcano is found at constructive plate boundaries?

A

Shield

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10
Q

How do volcanoes form at destructive plate boundaries?

A

When the oceanic plate melts in the subduction zone, plutons of magma rise to create volcanoes.

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11
Q

How do volcanoes form at oceanic ridges?

A

They occur as a result of sea floor spreading as magma rises through gaps in the crust and makes its way to the surface.

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12
Q

What type of lava is found at oceanic ridges?

A

Low viscosity, balsatic lava

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13
Q

How do volcanoes form at rift valleys?

A

When the crust drops down, the magma rises through the gaps as the crust becomes thinner.

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14
Q

What is meant by the term “active”?

A

An eruption is currently going on

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15
Q

What is meant by the term “dormant”?

A

It has not erupted in the last 2000 years

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16
Q

What is meant by the term “extinct”?

A

The volcano will not erupt again.

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17
Q

Give an example of an active volcano

A

Mauna Loa, Hawaii

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18
Q

Give an example of a dormant volcano

A

Mt Rainier, USA

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19
Q

Give an example of an extinct volcano

A

Mount Snowden, Wales

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20
Q

Where are shield volcanoes found?

A

Hotspots and constructive boundaries

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21
Q

What are composite volcanoes made of?

A

Alternating layers of ash and lava from previous eruptions.

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22
Q

What are shield volcanoes made of?

A

Lava

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23
Q

Where are composite volcanoes found?

A

Destructive plate boundaries

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24
Q

What are eruptions of composite volcanoes like?

A

Pyroclastic flows

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25
Q

What are eruptions of shield volcanoes like?

A

Lava flows

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26
Q

What is lava made of?

A

Silicon, oxygen, aluminium, iron, magnesium, calcium, sodium, potassium, phosphorus, and titanium

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27
Q

How do high viscosity lavas flow?

A

Slowly

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28
Q

How far do high viscosity lavas flow?

A

They cover small areas.

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29
Q

How do low viscosity lavas flow?

A

Quickly

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30
Q

How far do low viscosity lavas flow?

A

They cover thousands of square kilometres

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31
Q

Why do low viscosity lavas not result in violent eruptions?

A

Gases are allowed to escape so pressure does not build up.

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32
Q

Why do high viscosity lavas lead to violent eruptions?

A

Gas pressures build up.

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33
Q

What is the character of volcanoes largely controlled by?

A

The viscosity of the lava.

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34
Q

How is the magnitude of volcanoes measured?

A

Using the VEI

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35
Q

What does VEI stand for?

A

Volcanic Explosivity Index

36
Q

What is the VEI measured on a scale of?

A

0-8

37
Q

What does a VEI score of 0 suggest?

A

Non-explosive

38
Q

What does a VEI score of 8 suggest?

A

Very large

39
Q

Why might eruptions with the largest VEI scores not have the worst effects?

A

Volcano could be in a rural area with a small population
Prediction and evacuation
LIC/HIC
Population density

40
Q

List 4 potential primary impacts of volcanic eruptions

A

Tephra
Volcanic gases
Lava flows
Pyroclastic flows

41
Q

What is tephra?

A

Solid material of varying size that ranges from volcanic bombs to ash, all ejected into the atmosphere.

42
Q

What are the volcanic gases released by volcanoes?

A

CO2, CO, SO2, CL2 and hydrogen sulfide

43
Q

Give an example where volcanic gases have caused a problem

A

In 1986, CO2 emissions from a lake in the crater of Nayos, Cameroon killed 1700 people.

44
Q

What are lava flows?

A

Streams of molten rock that pour from an erupting vent

45
Q

What are pyroclastic flows?

A

Very hot, gas charged, high velocity flows made up of a mixture of gas and tephra.

46
Q

Give an example where pyroclastic flows have caused problems in the past

A

Pompeii was destroyed by pyroclastic flows from Mt Vesuvius in 79AD.

47
Q

What are 6 potential secondary impacts of volcanic eruptions?

A 
Lahars
Flooding
Volcanic landslides
Tsunamis
Acid rain
Climate change
48
Q

What are lahars?

A

Melted snow and ice as a result of the eruption combined with volcanic ash forms mud flows that can move down the course of river valleys at high speeds.

49
Q

Give an example of a deadly lahar

A

1985, a lahar destroyed the Columbian town of Armero after Nevado Del Ruiz erupted, only 25% of the population survived.

50
Q

Why can flooding occur after an eruption?

A

The eruption may melt glaciers and ice caps.

51
Q

When has flooding as a result of an eruption been a problem?

A

Iceland 1996, after the Grimsvotn volcano erupted.

52
Q

What are volcanic landslides?

A

Large masses of wet/dry rock and soil that fall, slide or flow rapidly under the force of gravity.

53
Q

What are volcano-related tsunamis caused by?

A

Violent volcanic eruptions

54
Q

Give an example when a tsunami caused by an eruption has been deadly

A

Krakatoa, Indonesia 1883, estimated 36,000 dead

55
Q

Why can eruptions cause acid rain?

A

Volcanic gases released containing sulphur mix with atmospheric moisture.

56
Q

Why can eruptions cause climate change?

A

Volcanic debris can reduce global temperatures.

57
Q

What are the 3 methods of mitigation?

A

Preparation, prevention and adaptation

58
Q

What visual change can suggest a volcano may erupt?

A

Ground deformation

59
Q

What do seismometers detect?

A

Small earthquakes

60
Q

What are the small earthquakes caused by? (In a volcanic context)

A

Magma rising up through cracks in the Earth’s crust

61
Q

What do thermal imaging techniques and satellites detect?

A

Rising temperatures as volcanic activity increases.

62
Q

What are gas samples and chemical sensors used for?

A

Detecting high sulphur levels which may indicate that the volcano will erupt soon.

63
Q

What are long-period events?

A

These indicate the movement of magma as a result of increased pressure on the rock and can be seen on seismometer readings.

64
Q

How many lives did the knowledge of long-period events save when Popocatepetl erupted?

A

30,000

65
Q

When did Popocatepetl erupt?

A

2000

66
Q

Where is Popocatepetl?

A

Mexico

67
Q

How do you spell the name of the Icelandic volcano that erupted in 2010?

A

Eyjafjallajokull

68
Q

What did the volcanic ash cloud released by Eyjafjallajokull in 2010 cause?

A

Flights in and out of the UK to be cancelled.

69
Q

Were there any deaths when Eyjafjallajokull erupted?

A

No

70
Q

What is expected for Eyjafjallajokull in the future?

A

Larger eruptions

71
Q

Tectonic plate boundaries are home to what percentage of volcanoes?

A

80%

72
Q

What type of plate boundary is Iceland on?

A

A constructive plate boundary?

73
Q

What is significant about Iceland’s location on a constructive plate boundary?

A

It will continue to grow

74
Q

What are 5 ways in which people can adapt for volcanic eruptions?

A 
Monitoring systems
Redrafted action plans
Relocation
Building techniques
Concrete shelters
75
Q

How can building techniques be used to mitigate the risks from volcanic eruptions?

A

Retrofit buildings

Stronger structures

76
Q

What are redrafted action plans based on?

A

Previous events

77
Q

What are 6 ways in which death and destruction by volcanic eruptions can be prevented?

A 
Location of infrastructure
Building techniques
Lava channels
Warning systems
Evacuation
Evacuation routes
78
Q

Where should businesses/schools and homes be built?

A

Away from volcanoes

79
Q

What type of building should be strategically placed?

A

Hospitals

80
Q

What do lava channels do?

A

Redirect lava away from buildings and people

81
Q

Why are clear evacuation routes important?

A

They can save lives and reduce the number of injuries.

82
Q

What are 7 ways in which people can prepare for volcanic eruptions?

A 
Emergency funds
Emergency supplies
Hazard maps
Evacuation
Exclusion zones
Communication systems
Education
83
Q

What do hazard maps show?

A

Pathways of expected eruption products

84
Q

What is important when planning an evacuation?

A

That there are places to temporarily relocate people.

85
Q

What is a benefit of exclusion zones?

A

They reduce disruption

86
Q

Why are communication systems important?

A

For coordinating rescue and give warnings or evacuation orders.

Hazards (15 decks)

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