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geography alevel > volcanic hazards > Flashcards

volcanic hazards Flashcards

1
Q

what is vulcanicity

A

refers to all volcanic activities related to magma being forced into the crust

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2
Q

what are volcanoes

A

are openings in the Earth’s crust through which lava, ash and gases erupt

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3
Q

what is the difference between magma and lava

A

Molten rock beneath the surface is referred to as magma,
but once it is ejected at the surface it is called lava

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4
Q

how man active volcanoes are there

A

1500

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5
Q

how many volcanic eruptions are associated with plate margins

A

95%

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6
Q

how many volcanic eruptions are associated with intraplate

A

5%

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7
Q

what plate margins are volcanoes found at

A
  • constructive (ocean crust)
  • constructive (continental crust)
  • destructive
  • intraplate over hot posts
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8
Q

how does magma differ between constructive and destructive plate margins

A

constructive = basaltic
destructive = acidic (andesitic and rhyolite)

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9
Q

how does lava differ between constructive and destructive plate margins

A

constructive = runny, less viscous and low silica
destructive = slow moving, viscous and high silica

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10
Q

how does the type of eruption differ between constructive and destructive plate margins

A

constructive = little violence, effusive, gases escape
destructive = potentially explosive

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11
Q

how does the frequency of volcanic eruptions differ between constructive and destructive plate margins

A

constructive = regular and may be continuous
destructive = from time to time, long dormant periods

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12
Q

what is the spatial distribution of volcanoes

A

most occur in linear belts along plate boundaries e.g pacific ring of fire

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13
Q

what is magnitude in relation to volcanoes

A

refers to its explosive power

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14
Q

what scale measures volcanoes

A

since 1982 magnitude has been measured by a logarithmic scale known as the volcanic exclusivity index

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15
Q

what is the scale of the vei

A

1-8

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16
Q

how can we accurately predict an eruption

A
  • vulcanologists need to know a volcanos eruption history
  • and be currently monitoring it
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17
Q

what are the warning signs volcanologist monitor

A
  • local seismic activity using seismometers, tremors indicate rising magma
  • ground deformation measured by tilts meters
  • changes in concentration of gasses e.g carbon dioxide and sulphur dioxide
  • rising temp of ground water
  • physical changes around the crater
18
Q

what is a primary impact

A

occur immediately afterwards and are a
direct result of the material ejected from the volcano

19
Q

what are examples of primary impacts from a volcanic eruption

A
  • lava and pyroclastic flows destroy roads and cause buildings to collapse
  • ash fall out may contaminate crops and water supplies
  • tephras may kill or injure people
20
Q

what are secondary impacts

A

occur in the days or weeks that follow and are indirectly related to the eruption itself, can be social, economic or environmental

21
Q

examples of secondary impacts from volcanic eruptions

A
  • Lahars can kill or injure people and can cause additional damage to roads and bridges, making it difficult for emergency services to reach people in need
  • People who have lost loved ones or their home or job in the eruption can experience psychological problems
  • Environmental impacts could include fires caused by lava flows and pyroclastic flows or damage to vegetation and fresh water habitats by acid rain
22
Q

what risk management can be taken to reduce impacts of volcanoes

A

prediction and protection including preparedness, mitigation and adaption

23
Q

what does prediction involve

A
  • accurate hazard mapping
  • analysing seismic shockwave patterns
  • sampling gas and lava emissions
24
Q

what is an example where prediction of volcanoes worked

A

2000 Mexico eruption of Popocatepetl, volcano erupted 48 hours after local population evacuation

25
Q

what does protection involve

A

reducing risk of damage by preparing
- warnings are issued
- instructions given on how to react before, during and after
- hazard mapping and land use planning to avoid development in at risk areas
- in at risk areas, alert systems, shelters and evacuation maps, emergency food and water supplies

26
Q

how can we adapt to volcanic eruptions

A

design solutions such as
- windows facing the volcano
- shutters for windows to make them air tight
- triple roof support for extra strength to prevent collapse
- steep slope roof and smooth roof material so ash is less likely to accumulate
- concrete rather than timber frames for additional strength

27
Q

what is a lava flow

A

Molten rock flowing over the surface. Basaltic (basic) lavas have higher temperatures and a low silica content (less than 52%), which means that they tend to flow some distance before solidifying (e.g. on the Hawaiian Islands). Acid lavas (either andesitic or rhyolitic) are more viscous; flow more slowly and often solidifies in the vent of the volcano, resulting in unpredictable and explosive eruptions

28
Q

what is a pyroclastic flow

A

A mixture of hot rock, lava, ash and gases rising from a volcanic eruption that moves at a rapid speed (up to 200m/s) along the ground. The most dangerous are those that erupt sideways due to a blocked summit crater. Temperatures are between 350- 1000oC. Pyroclastic flows are more common in eruptions of acidic lava at subduction zones

29
Q

what is a tephra

A

Solid rock fragments ejected during volcanic eruptions. The largest fragments can be over 1m in diameter and fall close to the volcano (potentially causing injury or death to people); the smallest fragments (ash less than 2mm) are carried by wind and travel great distances (vertically and laterally)

30
Q

what is a Nuees ardente

A

Means ‘glowing cloud’ and is a dense, rapidly moving cloud of hot gases, ashes and lava fragments from a volcanic eruption. It is a type of pyroclastic flow that contains more dense material and so doesn’t travel as far

31
Q

What is ash fallout

A

Ash can be ejected high into the atmosphere and, depending on prevailing winds, can cover a large area. Ash is highly abrasive and can cause breathing problems, disrupt machinery and clog filters. It can also obstruct sunlight, reducing visibility and temperatures

32
Q

What are volcanic gases

A

These are dominated by steam – often superheated – but also include carbon monoxide, hydrogen sulphide, sulphur dioxide and chlorine. These gases are highly dangerous

33
Q

what are mudflows/lahars

A

Lahars are destructive mudflows formed when ash and other volcanic material are mixed with water. They flow at speeds of up to 60km/h and are highly erosive

34
Q

what is acid rain

A

Volcanoes emit sulphurous gases, which can result in acidic rainwater when combined with atmospheric moisture

35
Q

example of a pyroclastic flow

A

AD 79 from Mount Vesuvius overwhelmed the Roman city of Pempeii

36
Q

what is an example of a lava flow

A

during 2014-15 eruption of Fogo Volcano in Cape Verde engulfed 75% of buildings within three villages

37
Q

what is an example of a tephra

A

2010 eruption of Eyjajallajokull led to the cancellation of 100,000 flights

38
Q

what is an example of a nuees ardente

A

1902 French Caribbean island of Martinique swept down the slopes of Mount Pelee killing all but 29,000 residents

39
Q

what is an example of ash fallout

A

2010 eruption of Eyjafjallajokull

40
Q

example of volcanic gasses

A

1986 -
At least 1,200 people were killed and
300 hospitalized when an underwater
volcanic explosion unleashed deadly gases at
Lake Nios in a remote area of northern
Cameroon

41
Q

example of a mudflow/lahar

A

November 13, 1985 small eruption produced enormous lahar that buried the town of Armero in Tolima causing an estimated 25,000 deaths - deadliest lahar in recorded history

42
Q

what is an example of acid rain

A

Tonga 2022 - Since the initial eruption, the volcano has been releasing sulfur dioxide and nitrogen oxide — two gases that create acid rain when they interact with water and oxygen in the atmosphere

geography alevel (14 decks)

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