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Volcanic Eruption Case Study

Volcano case studies

You should make sure you are familiar with 2 case studies:
Either: Nyiragongo, Democratic Republic of Congo - Poor Country or Montserrat, Caribbean - Poor Country
AND
Either: Mount St. Helens, USA - Rich Country or Iceland - Rich Country

Key terms:

Primary effects: the immediate effects of the eruption, caused directly by it
Secondary effects: the after-effects that occur as an indirect effect of the eruption on a longer timescale
 Immediate responses: how people react as the disaster happens and in the immediate aftermath 
Long-term responses: later reactions that occur in the weeks, months and years after the event

Nyiragongo

The video below contains more information on the primary and secondary effects of a volcano

On 17th January 2002 Nyiragongo volcano in the Democratic Republic of Congo (DRC) was disturbed by the movement of plates along the East African Rift Valley. This led to lava spilling southwards in three streams.

The primary effects - The speed of the lava reached 60kph which is especially fast. The lava flowed across the runway at Goma airport and through the town splitting it in half. The lava destroyed many homes as well as roads and water pipes, set off explosions in fuel stores and powerplants and killed 45 people 

The secondary effects - Half a million people fled from Goma into neighbouring Rwanda to escape the lava. They spent the nights sleeping on the streets of Gisenyi. Here, there was no shelter, electricity or clean water as the area could not cope with the influx. Diseases such as cholera were a real risk. People were frightened of going back. However, looting was a problem in Goma and many residents returned within a week in hope of receiving aid.

Responses - In the aftermath of the eruption, water had to be supplied in tankers. Aid agencies, including Christian Aid and Oxfam, were involved in the distribution of food, medicine and blankets.


Montserrat - Poor country case study

Mount St Helens - Rich country case study

Mount St. Helens is one of five volcanoes in the Cascade Range in Washington State, USA. The volcano erupted at 8:32am on 18th May 1980. 

Effects - An earthquake caused the biggest landslide ever recorded and the sideways blast of pulverised rock, glacier ice and ash wiped out all living things up to 27km north of the volcano. Trees were uprooted and 57 people died.

Immediate responses - helicopters were mobilised to search and rescue those in the vicinity of the catastrophic blast. Rescuing survivors was a priority, followed by emergency treatment in nearby towns. Air conditioning systems were cleaned after by clogged with ash and blocked roads were cleared. Two million masks were ordered to protect peoples lungs.

Long-term responses - Buildings and bridges were rebuilt. Drains had to be cleared to prevent flooding. The forest which was damaged had to be replanted by the forest service. Roads were rebuilt to allow tourists to visit. Mount St. Helens is now a major tourist attraction with many visitor centres.


Iceland - Rich country case study

Location:
Iceland lies on the Mid-Atlantic Ridge, a constructive plate margin separating the Eurasian plate from the North American plate. As the plates move apart magma rises to the surface to form several active volcanoes located in a belt running roughly SW-NE through the centre of Iceland. Eyjafjallajokull (1,666m high) is located beneath an ice cap in southern Iceland 125km south east of the capital Reykjavik

The Eruption:
In March 2010, magma broke through the crust beneath Eyjafjallajokull glacier. This was the start of two months of dramatic and powerful eruptions that would have an impact on people across the globe. The eruptions in March were mostly lava eruptions. Whilst they were spectacular and fiery they represented very little threat to local communities,
However, on 14th April a new phase began which was much more explosive. Over a period  of several days in mid-April violent eruptions belched huge quantities of ash in the atmosphere.

Local impacts and responses:
The heavier particles of ash (such as black gritty sand) fell to the ground close to the volcano, forcing hundreds of people to be evacuated (immediate response) from their farms and villages. As day turned to night, rescuers wore face masks to prevent them choking on the dense cloud of ash. These ash falls, which coated agricultural land with a thick layer of ash, were the main primary effects of the eruption.
One of the most damaging secondary effects of the eruption was flooding. As the eruption occurred beneath a glacier, a huge amount of meltwater was produced. Vast torrents of water flowed out from under the ice. Sections of embankment that supported the main highway in Southern Iceland were deliberately breached by the authorities to allow floodwaters to pass through to the sea. This action successfully prevented expensive bridges being destroyed. After the eruption, bulldozers were quickly able to rebuild the embankments and within a few weeks the highway was reconstructed.

Local impacts:
800 people evacuated
Homes and roads were damaged and services (electricity & water) disrupted
Local flood defences had to be constructed
Crops were damaged by heavy falls of ash
Local water supplies were contaminated with fluoride from the ash

National impacts:
Drop in tourist numbers - affected Iceland's economy as well as local people's jobs and incomes
Road transport was disrupted as roads were washed away by floods
Agricultural production was affected as crops were smothered by a thick layer of ash
Reconstruction of roads and services was expensive

International impacts:
Over 8 days  - some 100,000 flights were cancelled
10 million air passengers affected
Losses estimated to be £80 million
Industrial production halted due to a lack of raw materials
Fresh food could not be imported
Sporting events such as the Japanese Motorcycle grand prix, Rugby leagues challenge cup and the Boston Marathon were affected

International impacts and responses:
The eruption of Eyjafjallajokull became an international event in mid-April 2010 as the cloud of fine ash spread south-eastwards toward the rest of Europe. Concerned about the possible harmful effects of ash on aeroplane jet engines, large sections of European airspace closed down. Passenger and freight traffic throughout much of Europe ground to a halt.
The knock-on effects were extensive and were felt across the world. Business people and tourists were stranded unable to travel in to or out of Western Europe. Industrial production was affected as raw materials could be flown in and products could not be exported by air. As far away as Kenya, farm workers lost their jobs or suffered pay cuts as fresh produce such as flowers and bean perished, unable to be flown to European supermarkets. The airline companies and airport operators lost huge amounts of money.
Some people felt that the closures were an over-reaction and that aeroplanes could fly safely through low concentrations of ash. However, a scientific review conducted after the eruption concluded that under the circumstances it had been right to close the airspace. Further research will be carried out as a long-term response to find better ways of monitoring ash concentrations and improving forecast methods.


 

 

Left:  Mt. Pinatubo eruption plume, July 1991, from Clark Air Base control tower.  Photo by J.N. Marso, U.S. Geological Survey.

The effects of several historic eruptions have been observed and the impacts of larger, prehistoric eruptions can be estimated.

 

Estimates of the fraction of sunlight transmitted through stratigraphic aerosols after major eruptions. Roza refers to a flood basalt eruption in the northwestern United States. Graph from Rampino and others (1988).

 

The pages in this section explore the following case studies for their impact on global climate

Toba, 75,000 years ago
Laki, Iceland, 1783
Tambora, Indonesia, 1815
Krakatau, 1886
El Chichon, Mexico, 1982
Mt. Pinatubo, Philippines, 1991

 

Impact of some major historic eruptions.

Eruption

VEI  (Explosivity Index)

Magma Volume (km3)

Column height (km)

H2SO4 aerosols (kg)

Northern Hemisphere temperature decrease

Laki, 1783

4

14-15

 

<1 x10 11

about 1.0

Tambora, 1815

7

>50

>40

2x10 11

0.4-0.7

Krakatau, 1883

6

>10

>40

5x10 10

0.3

Santa Maria, 1902

6

about 9

>30

<2x10 10

0.4

Katmai, 1912

6

15

>27

<2x10 10

0.2

St.Helens, 1980

5

0.35

22

3x10 8

0-0.1

Agung, 1963

4

0.3-0.6

18

1-2x10 10

0.3

El Chichon, 1982

4

0.3-0.35

26

1-2x10 10

0.4-0.6

Data from Rampino and Self, 1984.