Vulcanicity- Case Studies Flashcards
What is the tectonic setting of Soufrière Hills?
- destructive margin where two oceanic plates move together
- formation of deep ocean trenches and volcanic island arcs due to subduction
What is the tectonic setting of Eyjafjallajökull ?
- one of Iceland’s smaller ice caps
- located in the far south of the island
- ice cap covers a caldera that is 1666m above sea level
What is the nature of the hazard in Soufrière Hills?
- continual eruptions of the volcano with biggest around July 1995
- violent tephra, ash and bombs
- 25th June; 4.3 million metres cubed of material
What was the nature of the hazard in Eyjafjallajökull?
- a fissure opened up 150m in length with 10-12 erupting craters
- lava 100 degrees C up to 150m in the air
- ejected fine glass-rich ash over 8km which was deflected East by westerly winds
What was the vulnerability of Soufrière hills?
- quite vulnerable; a small island that relies heavily on agriculture and is a relatively poor country
What was the vulnerability of Eyjafjallajökull ?
- a remote corner of Iceland where there is only a local, dispersed farming community so had minor local impacts
What was the capacity to cope in Soufrière hills
- quite prepared; US geologists already there as part of Volcano Disaster Assistance Program
- help from Britain but was criticised for late response
- hazard mapping and evacuation meant only 19 people died
What was the capacity to cope in Iceland?
- not much planning/preparation/prevention due to remote location of the volcano
What were the short term impacts in Soufrière hills?
- buildings, farmland and forest destroyed (economy)
- livestock killed
- Plymouth buried in over 10m of ash and mud
- airport and docking facilities destroyed
- Southern part of the island rendered uninhabitable
What were the short term impacts of Eyjafjallajökull
- a thick layer of ash fell on farm pastures
- local river levels rose because ice cap melted
- local gravel roads blocked by falling ash
What were the long term impacts in Soufrière hills
- tourist industry stopped completely
- loss of services and docking facilities = collapse in the economy
- unemployment rose from 7% to 50%
- mass migration and skills shortages
Long term impacts of Eyjafjallojökull
- air travel over North West Europe was disrupted majorly because the ash got into the polar jet stream
Immediate responses to Soufrière hills
- evacuation
- hazard mapping creating exclusion zones
- setting up of temporary shelters in the north
Immediate responses to Eyjafjallajökull
- 500 local farmers evacuated overnight
- roads closed because of fears of flash floods
Long term responses to Soufrière hills
- financial help with resettlement from the UK (£2500)
- resettlement of population in the safer north
- re-establishment of air and sea links
- new permanent housing built
- moving of capital from Plymouth to Salem
- farming areas provided in the north
- setting up of Montserrat Volcano Observatory (MVO)
Long term responses to Ejyafjallajokull
- flights of NW European countries stopped 14th-21st April
- sporadic disruption to flights for several days
- six day shutdown estimated to have cost airlines 1.2 billion pounds
What are the comparison case studies?
Chances Peak, Soufrière Hills, Montserrat (1997)
Eyjafjallajökull, Iceland (2010)
Case studies for planning and prediction
- Sakurajima, Japan
- Soufrière Hills, Montserrat
- Mount Unzen, Japan
General facts about Sakurajima, Japan
- one of the most monitored volcanoes on earth
- lies near Kagoshima city, where 500,000 people live
Observation techniques used in Sakurajima, Japan
- swelling of land around the volcano
- earthquakes detected between 2-5km below the surface
- bore holes with temperature detectors
- a network of tilt meters detect every movement of the mountain
- seismometers detect earthquakes which occur immediately beneath the crater, signalling an eruption
Observation used in Montserrat
Monitoring, evacuation, public information and exclusion zones used
Success of Montserrat
- only 19 deaths and these were islanders that refused to leave their homes
- however much of the island was destroyed including the capital of Plymouth and a whole new infrastructure had to be built afterwards
General facts about Mount Unzen, Japan
- explosion in 1991, had been dormant for nearly 200 years
Planning in Mount Unzen, Japan
- a lava come appeared in May 1991 so the government issued an evacuation order and made a restriction zone
- 12,000 people were evacuated in June when the eruption increased in intensity
Success of Mount Unzen
The civilian population was protected; those who died were people from the media/science who willingly went into the danger zone
Case studies for direct control of the hazard
- Mount Etna, Italy
2. Eldfell, Heimaey
What happened in Mount Etna
- lava flow from 1991-1993 threatened the town of Zafferana
- earth barriers were constructed to divert lava but were overcome
- explosives were set off to disrupt a 7km lava tube system
- the explosion diverted the lava into a man made tube and the eruption queitened down, the town stayed safe
What happened in Eldfell, Heimaey
- an island off the South west coast of Iceland
- a fissure opened up from one length of the shore to the other
- the population was evacuated by fishing fleet
- they were determined to save their harbour so pumped millions of tonnes of sea water into the advancing lava front to cool the flow
- this worked and the lava flow enhanced the harbour entrance
