3.1.5.3 - Volcanic Hazards Flashcards

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1
Q

How are volcanoes formed at oceanic ridges and what is a key example of this

A

When the plates move apart magma forces its way up to the surface where it cools and forms a new crust - as the plates move the new crust moves further away
- Eyjafjallajokull

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2
Q

How volcanoes formed on or near subduction zones, why are the volcanoes viscous and explosive and what is an example where lots occur

A
  • the heat generated from the inside of the earth and from the friction between the two plates causes the oceanic plate to melt.
  • as its less dense it rises as plutons of magma until reaching the surface and forms volcanoes
  • andesitic lava causes viscous and explosive volcanoes
  • e.g. ring of fire
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3
Q

How are volcanoes formed at rift valleys and a key example

A
  • when the continental plates move apart areas of the brittle crust drop between forming rift valleys
  • this crust is thinner meaning magma can force its way to the surface easily forming volcanoes
  • e.g. Mount Nyrigongo
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4
Q

What are hot spots, how do they cause volcanoes and a key example

A
  • = concentration of radioactive elements
  • causes plumes of magma to rise and eat into the plate above
  • when the magma breaks through, active volcanoes form above the spot
  • plates moves along the hot spot forming a chain of islands e.g. Hawaiian islands
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5
Q

Why are volcanoes formed at hot spots cause shield volcanoes and how have the old volcanoes been reduced to seamounts

A
  • basaltic lava flows slowly and forms huge flattish volcanoes = shield volcanoes
  • due to marine erosion and subsidence caused by the pressure the volcanoes puts on the crust
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6
Q

Where are three key places that volcanoes are found

A
  • ring of fire (surrounding pacific ocean)
  • Rift in Africa
  • Hawaiian hot spots
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7
Q

What is used to measure the magnitude of volcanoes and what is used to determine the magnitude

A
  • volcanic explosivity index

- the volume of erupted material

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8
Q

How can volcanologists track the frequency of a volcanoes eruption

A
  • a volcanoes previous history of activity is tracked using deposits associated with the volcano and how old or deep they are
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9
Q

What are 6 ways volcanologists can predict when a volcano is going to erupt or close to erupting

A
  • monitor land swelling - could mean magma is moving to the main chamber
  • changes in the groundwater levels - if groundwater levels rise then magma could be forcing its way toward the surface
  • chemical composition of groundwater - poisonous gases can seep from the ground, water can get hotter so thermal monitoring is used
  • Shock waves caused from magma moving towards the surface
  • mass movements like landslides suggests upwelling of magma
  • magma movement can be tracked using magnometres
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10
Q

What are 3 ways we can protect from volcanoes

A
  • monitoring allows for prediction which allows for evacuation
  • studying the nature and extent of deposits from lahars and lavas which allow to identify places at great risk and therefore influence land use planning
  • viscous lava can be diverted through digging trenches or splashing seawater on it to solidify it
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11
Q

What are the 4 primary effects of volcanoes and how do they impact people

A
  • tephra = solid material of varying grain size (vary from volcanic bombs to ash) - climate change, aviation, breathing issues
  • pyroclastic flows = very hot, gas charged flows containing a mixture of gas and tephra - can flow up to 700kmph so are a high cause of death as they hard to escape
  • Lava flows - destroy buildings and can cause death
  • Volcanic gases (e.g. CO2, carbon monoxide and Sulphur dioxide )- can cause climate change and acid rain
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12
Q

6 secondary effects of volcanoes and how do they occur

A
  • Lahars (volcanic mud flows) = when snow or ice melts caused by an eruption and they combine with volcanic ash to form fast flowing mud flows
  • Flooding - when an eruption causes glaciers or ice to melt
  • Volcanic landslides - the shaking from the eruption causes rocks to move and mass movements to occur
  • Tsunami’s - from violent eruptions the ground shakes causing a tsunami to occur
  • Acid rain - Sulphur emitted from volcanic eruption combines with the moisture in the air
  • Climate change - the emission of CO2 contributes to global warming
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13
Q

Case study

- Where is Mt Nyiragongo located, what is it associated with and when did it erupt

A
  • Democratic republic of congo
  • the african rift valley
  • January 2002
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14
Q

Case study

- What were the 3 characteristics of the main crater of the volcano

A
  • 250m deep
  • 2km wide
  • ‘lava lake’
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15
Q

Case study

What encouraged many people to settle down in Goma despite the risk of the volcano

A

It was a fertile agricultural region because :

  • It has an extended growing season
  • the volcanic soils are very fertile
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16
Q

Case study

What are people from Goma particularly vulnerable to that the local people call ‘Mazuku’

A

Poisonous carbon dioxide seeping from the ground

17
Q

Case study

What are 4 economic primary effects of the eruption and 2 social primary effects of the eruption

A

Economic-
- lava flows destroyed 1/3 of Goma
- covered the northern third of the runway at airport Goma
- Commercial centre and water and power facilities were destroyed
- 3 health centres and 1 hospital were destroyed
Social-
- The death toll = 147
- 350,000 people had to be evacuated/fled to Rwanda where they struggled for food and shelter

18
Q

Case study

3 social secondary effects and 2 economical secondary effects

A

Social-
- Thousands were injured and required medical attention from eye irritation, respiratory problems or even from drinking contaminated water
- looting of houses and commercial properties - many people died when a petrol station they were looting blew up
- Large unemployment through destroyed businesses
Economical-
- Several earthquakes followed the eruption one on Richter scale 5 which caused industrial damage
- Destroyed businesses which caused unemployment

19
Q

Case study

- How did sulphorous lave entering lake kivu have a social and environmental secondary effect

A
  • Environmental = contaminated lake kivu killing wildlife as well
  • Social = it was a major drinking source so it was difficult for many people to access clean water
20
Q

Case study

What was an immediate short term response and what 4 things did the UN provide that cost around $15m

A
  • authorities issued a red alert for Goma and surrounding areas enabling for a full evacuation and was a big reason for such a low death toll
  • UN provided : emergency rations, set up camps for displaced people, health care and water
21
Q

Case study

What is a long term response and why is it both expensive and difficult

A
  • rebuilding homes, infrastructure and livelihoods
  • expensive as much of Goma was destroyed
  • difficult as the loss of businesses meant large unemployment which made it hard to rebuild livelihoods
22
Q

Case study 2

Why was vulnerability to Eyjafjallajökull very low

A
  • not many people live in that part of iceland
23
Q

Case study 2

What is a key characteristic of the volcano and what is the 3 step process of it causing large ash clouds

A
  • covered by an ice cap
  • 1) When magma hits the ice cap it suddenly cools forming a glass-like material which instantly disintegrates
    2) Explosions of gas from the main vent pulverise this glass-like material into very tiny particles
    3) These particles are carried in the ash and as it gets further away from the volcano it becomes invisible - can be sucked into engine
24
Q

Case study 2

When did the volcano erupt and and what was it on the VEI

A
  • April 14th 2010

- 4 on the scale

25
Q

Case study 2

What were the 2 impacts of the eruption and how did they have a social, economic and environmental impact

A
  • The eruption caused large amounts of ice to melt causing floods to rush down the nearby river and 1,000 people to be evacuated (social)
  • Large quantities of ash into the atmosphere (environmental) and blown towards Europe in the jet stream - Cost an estimated £130m for the six days airspace was shut (economic)
26
Q

Case study 2

Now that Eyjafjallajökull is considered dormant why is the neighbouring Kalta earthquake a concern

A
  • When it last erupted in 1918 it produced 5 times the amount of ash Eyjafjallajökull did in 2010
  • there are signs magma is rising beneath Kalta and therefore could be close to erupting