Volcano Case Studies

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  • Created by: FloraD
  • Created on: 05-06-16 09:24

Heimaey

Date: 1973

Margin: Divergent (constructive) Basic lava - basaltic

Plates: American - Eurasian

Eruption type: Fissure - Effusive

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Physical Events

PHYSICAL EVENTS

  • Ash build up of half a metre every hour
  • 100m3 of lava flow every second
  • snow falls

HUMAN SITUATION/VULNERABILITY

  • People moving their possesions out of their homes to prevent damage
  • The 5,300 people of Heimaey were mainly rescued by sea - some old and ill were airlifted
  • Due to severe stroms just days before the eruption, the whole fishing fleet was in the harbour
  • Defensive barriers were created to prevent lava flows
  • Water was pumped onto the oncoming lava 
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Long and Short Term Effects

Short Term Effects

  • Over 300 buildings destroyed
  • Lava flows broke through gates
  • 60-70 homes has been buried by tephra
  • Carbon dioxide, with small amounts of poisonous gases became concentrated in some buildings
  • Only 1 death - man suffocated upon breaking into a chemists to get drugs

Long Term Effects

  • Tephra covered the island and was 5 metres deep in places
  • By the end of March, a fifth of the town had been covered in lava flows
  • 32 pumps (for water) has been brought in from the USA
  • Knowledge and understanding was gained from the experience
  • The harbour became safer - more sheltered
  • Used the latent heat from the remaining lava to heat water/homes
  • The tephra was used to extend the runway and also for landfill, upon which 200 new houses were built.
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Nyiragongo

Date: 2002

Margin: American Rift Valley - Divergent Margin

Plates: Merican Plate - Cratons

Eruption Type: Fissure - Effusive - ash & flowing lava

Nyiragongo is a stratovolcano in east Africa's rift valley in the Democratic Republic of Congo.

Volcanism in this region results from tension and stretching of the continental crust and lithosphere.

Nyiragongo has an enormous summit crater - over 500m deep, this crater contains an active lava lake. 

Sometimes, crack develop in the crater, causing lava to drain out = 2002

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Physical Events

Physical Events

  • Lava drained from the crater and poured down the volcano's steep eastern and southern slopes, into the nearby city of Goma
  • Lava flows were 50m across and 6m high
  • Toxic gases released - vents on the slope released 50,000mcf
  • Acid rain was created as a result of the formation of sulfur dioxide emitted by the eruption

Human Situation/Vulnerability

  • 500,000 live in Volcano's shadow & Nyiragaongo is one of Africa's most active volcanoes
  • The local population is poor, depends heavily on subsistence farming, and has few resources to buffer it against natural hazards
  • 400,000 people were evacuated with thousands fleeing to neighbouring Rwanda where they were housed in temporary shelters
  • Vulnerability was also increased by the civial war in the Congo at the time - poor economic conditions
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Long and Short Term Effects

Short Term Effects

  • 110 people died
  • One fifth of Goma was destroyed 
  • 120,000 people became homeless after the eruption
  • The water treatment plant, hospital and cathedral were flattened
  • Lava flowed across the runway at Goma's airport - preventing large aircraft landing and hindering emergency relief

Long Term Effects

  • Fear that infectious diseases would spread through the population due to poor sanitation, people living in overcrowded refugee camps and shortages of portable drinking water
  • Cholera and diarrhoea were contained 
  • Leaflets have been distributed to raise awareness of the risks
  • Videos made that explain the hazards and the early warning and evacuation procedures.
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Montserrat

Date: 1995 - present

Margin: Convergent - destructive - acidic lava - andestic - viscous

Plates: North American & Caribbean

Eruption Type: Composite Cone & Explosive

The island of Montserrat owes it's existence to the Soufriere Hills stratovolcano.

Principle hazards are pyroclastic flows, tephra falls, debris avalanches and occasional lava flows.

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Physical Events and Human Vulnerability

Physical Effects 

  • Pyroclastic flows, tephra falls, debris avalanches and lava flows 
  • These generally create fires

Human Vulnerability

  • The inhabitants had been evacuated 3 times previously to the eruption which thus created a 'creid wolf' effect - few of the inhabitants were willing to evacuate again - thought it was another false alarm
  • Refuge camps were ready ad in palce
  • Designated the southern half of the island an exclusion zone and evacuating its population to safe areas in the north
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Long and Short Term Effects

Short Term Effects

  • 19 people dies in eruption
  • Plymouth (capital) was destroyed
  • The airport was also destroyed
  • Two thirds of the island uninhabitable
  • fertile agriculture land destroyed by ash falls and pyroclastic flows

Long Term Effects

  • 5,000 people migrated out of Montserrat
  • Half the displaced population migrated overseas and settled permenantly in UK and USA and nearby islands such as Antigua
  • Tourism sector damaged
  • New airport has been rebuilt
  • UK and EU have spent £200 million on regeneration projects
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Martinique

Date: 1902

Margin: Convergent - destructive - acidic lava - andesitic

Plates: North America & Caribbean

Eruption Type: Comosite & Explosive

Mount Pelee is a semi-active volcano on the northern end of Martinique. It's volcanic cone is composed of layers of volcanic ash and hardened lava.

Mount Pelee is the result of a typical subduction zone

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Physical Events and Human Vulnerability

Physical Events 

  • Lots of warning - boiling lake in crater near the summit - volcanic activity
  • A mini tsunami occured as well
  • Lahars, ash clouds and pyroclastic flows
  • A notch became apparent in the crater

Human Vulnerability

  • No one was allowed to leave due to upcoming elections
  • People moved to urban areas in an attempt to keep safe
  • 'cry wolf' idea
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Long and Short Term Effects

Short Term Effects 

  • 30,000 died in eruption
  • The town of St.Pierre destroyed
  • Only 1 real survivor - prisoner in concrete prison - severe burns
  • First time a pyroclastic flow had been identitfied

Long Term Effects

  • The plantations did not recover - economy suffered hugely
  • Tourism was lost shortly but has started again - curiosity over volcano 
  • Part of the island was vener developed
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