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Geography A-level > Volcanic hazards > Flashcards

Volcanic hazards Flashcards

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1
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2
Q

What is the spatial distribution of volcanoes?

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3
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What are hot spots?

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4
Q

What is the VEI?

A

A volcani richer sacle used since 1992 using logarithmic scale from 0-8 volanic explosivity index
Compares size of volcanic eruption (magnitude) by measuring amount and height of matter ejcted and how long the eruption lasted

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5
Q

Shield volcano

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Shallow-sided amd wide found at constructive plate margins and formed of balsaltic lava

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6
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Composite volcano

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Steep-sided and tall found at destructive plate margins formed of andesitic and rhyolitic lava

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7
Q

Lava

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Molten rock above the earths surface

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8
Q

Type of magma ? Characeristics? E.gs?

Hawaiian Volcanoes

A
  • Type of magma: basaltic
  • Characteristics: Active, lava flows gently from central vent
  • E.g.: Kilauea, Hawaii
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9
Q

Type of magma ? Characeristics? E.gs?

Strombolian volcanoes

A
  • Type of magma: Thicker basaltic
  • Characteristics: Frequent explosive eruptions of tephra and steam and occasional short lava flows
  • E.g.: Mount Etna, sicily
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10
Q

Type of magma ? Characeristics? E.gs?

Pillian volcanoes

A
  • Type of magma: Rhyolotic
  • Characteristics: Exceptionally violent eruptions of gases, ash and pumice, torrential rain storms cause devestating lahars
  • E.g.: Moount vesuvis italy
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11
Q

Type of magma ? Characeristics? E.gs?

Icelandic volcanoes

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  • Type of magma: Baslatic
  • Characteristics: Lava flows gently from fissures
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12
Q

Type of magma ? Characeristics? E.gs?

Vulcanian volcanoes

A
  • Type of magam: Baslatic, desitic and rhyolitic
  • Characteristics: Less frequent but more violent eruptions of gases ash and tephra
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13
Q

Type of magma ? Characeristics? E.gs?

Vesuvivian volcanoes

A
  • Type of magma: basaltic andestic and rhyolitic
  • Characteristics: following long periods of inactivity very violent gas explosions blast ash high into the sky
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14
Q

Type of magma ? Characeristics? E.gs?

Peleean volcanoes

A
  • Type: Andesitic and rhyolitic
  • Characteristics: Very violent eruptionsof nuees ardneees
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15
Q

What are primary effects?

A
  • Tephra
  • Prycolastic flows
  • Lava flows
  • Volcanic gases
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16
Q

Tephra

A

Solid material of varying grain size ranging from volcanic bombs to ash all ejected into the atmosphere
* Larger the particle shorter distance of travel from source
* Volcanic bombs are very dangerous people tend to avoid them
* Fine ash can be thrown into atmosphere and strong winds blows it around the earth reducing incoming radiation and cooling the earth

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17
Q

Pyroclastic flows ( nuees ardentes)

A

Very hot (over 800 degrees gas charged high velocity flows made up of a misture of gas and tephra
Hug ground and flow down sides of volcanoes up to 700km p/h

  • in 2018 flows from volcan de fuego guatemealakilled as many as2900 peopleand destroyed on estimated8500 hectares of agriculture land
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18
Q

Lava flows

A
  • lava can flow quickly or slowly depending on its viscosity.
  • Silica makes lava viscous and slow, which is common in explosive eruptions.
  • Rarely cause injury to people due to their relativley low velocity
  • ## Often unstoppable so damage crops, buildings and block roads
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19
Q

Volcanic gases

A
  • released during some eruptions, even CO₂ can be toxic as it can replace oxygen as it is heavier
  • Carbon dioxide, carbon monoxide, hydrogen sulphide, sulphur dioxide and chlorine
  • In 1986 co2 from lake in the crater of nyos camerons killed..
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20
Q

Secondary effects (natural ) (volcanoes)

A
  • Lahars
  • Flooding
  • Volcanic landslides
  • Tsunamis
  • Acid rain
  • Climate change
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21
Q

Lahars

A

Lahars = unconsolidated ash from recent eruptions combined with water may be swept down river valleys in the form of hot, dense, fast moving mud flow
* Water can come from heavy rain e.g. mount pinatubo, phillippines in 1991
* Melting snow and ice e.g. nevada del ruiz columbia 1985 completley destroyed the town of armeno 28,000 survived

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22
Q

Flooding

A

Flooding = when an eruption melts glaciers and ice caps
E.g. iceland in 1996 grimsvton

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23
Q

Volcanic landslides

A

Volcanic landslides = range in size from less than 1km3 to more than 100km 3
* High velocity and great momentum of landslides allows them to cross between valleys and run up slopes several metres high
* E.g. the landslide at mount st helens in 1980 had a volume o 2.5km reached speeds of 50-80 m/s and surged up over a 400m high ridge located 5km from volcano

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24
Q

Tsunamis

A

Tsunamis = sea waves generated by violent volcanic eruptions such as those formed after the eruption of Krakatoa (indonesia) in 1883. This tsunami killed 36,000 people

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25
Q

Acid rain

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Acid rain = volcanoes emit gases which include sulphur. When this combines with atmospheric moisture acid rain forms

26
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Climate change

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Climate change = the ejecetion of huge amounts of volcanic debris into the atmosphere can reduce global temperatures and is believed to have been an agent in past climate change

27
Q

Short term responses

A

Short term responses (saving lives)
* Depends on magnitude and vulnerability of the population
* Priority of saving lives
* Evacuation
* Deploying emergency servives to provide first response treatment
* Some international aid may be given

28
Q

Long term responses

A

Long term responses (preserving lives)
* Involves long term planning in future preparedness, mitigation, prevention and adaptation
* Introduction of volcanic monitoring, hazard mapping, evacuation plans to prevent future loss of life
* Stockpiling of food and water supplies for future use

29
Q

Preparation ( volcanic eruption)

A
  • Monitoring and prediction allows time for evacuation (people fear losing farmland and homes e.g. pinatubo)
  • In iceland this is done by icelandic meterological office
  • Training of emergency services
  • Observation stations e.g. Monserrat

Iceland:
* Vistors encouraged to download 112 app which send text messages should and eruption be imminent
* Hekla in particular is closley monitored as it is underneath the flight path

30
Q

Mititgation ( Volcanic eruption)

A
  • Aid (domestic or from overseas)
  • Monitoring to predict future eruptions
  • Creating alert systems (sirens, speakers and social media) to warn public of threat alert (e.g. New Zealand)
  • Evacuation camps for displaced people
  • Stockpiling of emergency food and water supplies
  • Diverting lava flows by digging trenches. dropping blocks into lava and using explosives e.g. etna or hawaiia
31
Q

Prevention (stopping completely)

A
  • Is this possible
  • Advantages of volcanic events such as the Ash is a nutrious fertiliser for crops
32
Q

Adaptation ( changing or adopting behaviour )

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  • Hazard mapping, exclusion zones, land use zoning to show high risk areas from Lahars and Lava flows
  • Using ash for building materials
33
Q

What is relief Parks model?

A

Relief is the immediate local and possibly global response in the form of aid, expertise and search and rescue

34
Q

Rehabilitation

A

A longer phase lasting weeks or months, when infrastructure and services are restored, albiet possibly temporarily to allow the reconstruction phase to begin as soon as possible

35
Q

Reconstruction

A

Restoring to the same, ot better, quality of life as before the evet took place. This is likely to include measures to mitigate against a similar level of disruption if the event occurs again

36
Q

```

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Benefits and drawbacks of Parks model of human response to hazards?

A
  • Could be considered better than HMC as it is time-linked
  • Developed and devloping countries can easily be compared - one takes longer to recover than the other
  • Multi-hazard zone may never reach normality if the rehabilitation stage takes a long time
37
Q

What is the top of tha arrow?

A
  • Return to normality
  • Improved qol
  • “Build Back Better” e.g. in 2011 tsunamis in japan walls are now higher than previously
38
Q

Examples of root causes

A

Low access to resources, Limited influence in decision making, Poor governance and weak economic system

39
Q

Examples of dynamic pressures

A

Lack of education,training and investment, Rapid population change and urbanisation

40
Q

Examples of unsafe conditions

A

Poor construction standards, unsafe infrastructure, poverty, lack of social saftey net

41
Q

Lithosphere

A

The layer of earth consisting of the rigid crust and upper section of the mantle

42
Q

Athenosphere

A

The part of the mantle which lies directly beneat the lithosphere made of molten and semi molten rocks

43
Q

Key facts about structure of earth

A
  • Helps to understand why tectonic hazards occur
  • Theory of plate tectinics has revolutionised
  • Earths outershell is the curst and thickness between 5 and 10km beneat the oceans to nearly 70km under the continents
  • Rocks in upper mantle are solid anf sit on top of athenosphere, softer almost plastic like rock which moves very slowly
  • As earth rotates liquid outercore spills, earths magenetic field
  • Cores internal heat is major cause fo earths tectonic activity
  • Some heat may primeval - retained from the ball of dust and gas from which the earth evolved
  • Earths greatest source of heat energy is from radioactivedecay (natural radioactive decay from euranium, thorium, potassium and other elements provides a continoous buy slowly diminishing heat
  • Heat at core generates convection currents within mantle
44
Q

oceanic crust

A

An occasionally broken layer of balsaltic rocks known as sima ( made up of silicia and magenesium)

45
Q

continental crust

A

Bodies of mainly granictic rocks known as sial (silia and alumnumin)

46
Q

core

A

The core is the centre and hottest part of the earth - reaches up to 6000 degrees celcius and is mostly made up of iron and nickel and is 4x more dense than the crust

47
Q

inner core

A

inner core = solid and made up of iron nickel alloy

48
Q

outer core

A

outercore = semiliquid and is mainly iron

49
Q

Krakatoa (indonesia) in 1883.

A

Krakatoa (indonesia) in 1883. This tsunami killed 36,000 people

50
Q

Andestic lava

A

Andestic lava has high viscosity and is more runny with a high silica content and more disolved gases and is more likley to explode when reaches surface

51
Q

Basaltic lava

A

Baslatic lava has low silicia content and relativley fluid because of its low viscosity

52
Q

Rhyolitic lava

A

Rhyolitic lava is a type of volcanic rock that is high in silica content, typically greater than 70%
* It has a very thick and viscous consistency, which influences how it flows and erupts1.
* Rhyolitic lavas tend to form thick blocky lava flows or steep-sided piles of lava called lava domes23.
* They erupt explosively, often producing abundant ash and pumic

53
Q

Short term responses

A
54
Q

Short term responses to volcanic acitivities ( saving lives)

A
  • Depends on magnitude and vulnerability of population
  • Priority of saving lives
  • Evacuation
  • Deploying emergency services to provide first response treatment
  • Some international aid to be given
55
Q

Long term responses ( preserving lives

A
  • Involves long-term planning in future preparedness, mitigation, prevention and adaptation
  • Introduction of volcanic monitoring, hazard mapping, evacuation, plans to prevent future loss of life
  • Stock piling of food and water supplies for future use
56
Q

Preparation (state of readiness of a volcanic eruption)

A
  • Monitoring and prediction allows time for evacuation (jhowever, people fear losing their farmland and homes e.g. Mount pinatubo) (icelandic meterological office)
  • Training of emergency services
  • Observation stations e.g. monsterrat
  • People monitor increase in release of various gases, Rise in level of lava lakes in volcanic crarers, Bulging upwards of surrounding land due to pressure below, increasing numver of relativley small eqs caused by rising magma, study of previous volcanic eruptions

Iceland:
Encourages tourits to download 112 app which send text messages should an eruption be imminent
Hekla is closley monitored as it is undernetah flight path those will have 15-30 warning time

57
Q

Mitigation of volcanic hazards

A
  • Risk assesments carried out by governments in countries at risk of volcanic hazards (phillipines) and produce series of alert levels to warn the public
  • Once viscious lava has staryed to flow it can be possible to divert it from built eruption e.g. in Mt etna in sicility digging trenches, droppungf blocks into lava stream and using explosives slows down flow, diverting it
  • 1973 haeimaey iceland poured sea water on front of lava flow to solidify it before it cut off their fishing port
  • Hawaiian islands have built barries across valleys to protect settlements from lava flow and lahars
  • Evacuation, exlusion zones (monserrat)
58
Q

Prevention

A

Not possible to prevent eruption but can be reduced by mitigationb
evacuation
Benefits of living in proximity of eruption

59
Q

Adaptation

A
  • Hazard mapping, exclusion zones and land use zoning to show high risk areas from lahars and lava flows e.g. monserrat
  • Using ash for building materials
60
Q
A

Geography A-level (21 decks)

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