Vulcanicity- Case Studies

Question 1

What is the tectonic setting of Soufrière Hills?

Answer 1

• destructive margin where two oceanic plates move together

- formation of deep ocean trenches and volcanic island arcs due to subduction

Question 2

What is the tectonic setting of Eyjafjallajökull ?

Answer 2

• 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

Question 3

What is the nature of the hazard in Soufrière Hills?

Answer 3

• continual eruptions of the volcano with biggest around July 1995
• violent tephra, ash and bombs
• 25th June; 4.3 million metres cubed of material

Question 4

What was the nature of the hazard in Eyjafjallajökull?

Answer 4

• 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

Question 5

What was the vulnerability of Soufrière hills?

Answer 5

• quite vulnerable; a small island that relies heavily on agriculture and is a relatively poor country

Question 6

What was the vulnerability of Eyjafjallajökull ?

Answer 6

• a remote corner of Iceland where there is only a local, dispersed farming community so had minor local impacts

Question 7

What was the capacity to cope in Soufrière hills

Answer 7

• 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

Question 8

What was the capacity to cope in Iceland?

Answer 8

• not much planning/preparation/prevention due to remote location of the volcano

Question 9

What were the short term impacts in Soufrière hills?

Answer 9

• 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

Question 10

What were the short term impacts of Eyjafjallajökull

Answer 10

• a thick layer of ash fell on farm pastures
• local river levels rose because ice cap melted
• local gravel roads blocked by falling ash

Question 11

What were the long term impacts in Soufrière hills

Answer 11

• 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

Question 12

Long term impacts of Eyjafjallojökull

Answer 12

• air travel over North West Europe was disrupted majorly because the ash got into the polar jet stream

Question 13

Immediate responses to Soufrière hills

Answer 13

• evacuation
• hazard mapping creating exclusion zones
• setting up of temporary shelters in the north

Question 14

Immediate responses to Eyjafjallajökull

Answer 14

• 500 local farmers evacuated overnight

- roads closed because of fears of flash floods

Question 15

Long term responses to Soufrière hills

Answer 15

• 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)

Question 16

Long term responses to Ejyafjallajokull

Answer 16

• 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

Question 17

What are the comparison case studies?

Answer 17

Chances Peak, Soufrière Hills, Montserrat (1997)

Eyjafjallajökull, Iceland (2010)

Question 18

Case studies for planning and prediction

Answer 18

1. Sakurajima, Japan
2. Soufrière Hills, Montserrat
3. Mount Unzen, Japan

Question 19

General facts about Sakurajima, Japan

Answer 19

• one of the most monitored volcanoes on earth

- lies near Kagoshima city, where 500,000 people live

Question 20

Observation techniques used in Sakurajima, Japan

Answer 20

• 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

Question 21

Observation used in Montserrat

Answer 21

Monitoring, evacuation, public information and exclusion zones used

Question 22

Success of Montserrat

Answer 22

• 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

Question 23

General facts about Mount Unzen, Japan

Answer 23

• explosion in 1991, had been dormant for nearly 200 years

Question 24

Planning in Mount Unzen, Japan

Answer 24

• 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

Question 25

Success of Mount Unzen

Answer 25

The civilian population was protected; those who died were people from the media/science who willingly went into the danger zone

Question 26

Case studies for direct control of the hazard

Answer 26

1. Mount Etna, Italy

2. Eldfell, Heimaey

Question 27

What happened in Mount Etna

Answer 27

• 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

Question 28

What happened in Eldfell, Heimaey

Answer 28

• 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