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Unlock This CourseThe spec asks for one detailed example of a named volcano. Ours is the 2010 eruption of Mount Merapi. We use ideas from Types of Volcano and Their Features, Volcanic Hazards, Impacts of Earthquakes and Volcanic Eruptions, Responses, Monitoring and Prediction and Protection, Planning and Technology. Here we apply them, not teach them again.
Location: Merapi is on the island of Java in Indonesia, in South-east Asia. It lies about 30 km north of the city of Yogyakarta. Indonesia was an MIC in 2010. Merapi means 'mountain of fire' and it is one of the most active volcanoes in the country.
Named places to use in an answer: Yogyakarta and its airport, the district of Sleman, the village of Kinahrejo, the Gendol and Code rivers, and Borobudur temple.
25 October 2010: the highest alert level is issued and a 10 km exclusion zone is set.
26 October: the first explosive eruption begins in the evening.
3 November: the exclusion zone is widened to 15 km.
5 November: the biggest eruption takes place, and the zone grows to 20 km.
Mid to late November: activity slowly weakens.
December 2010: the alert level and exclusion zone are reduced.
This was a known risk. Merapi had erupted many times before, so scientists were already watching it closely.
| Type | Impacts |
|---|---|
| Social | More than 340 people died, many of them killed by pyroclastic flows. About 350,000 people were evacuated and lived in shelters for weeks. More than 2,000 homes were destroyed. Schools were closed and shelters were crowded. |
| Economic | Losses were several hundred million US dollars (estimates range from about 450 to 780 million). Farmland, crops and cattle were lost, and farmers on the slopes lost their income. Tourism near Yogyakarta fell. Yogyakarta airport closed and many flights were cancelled because of the ash. |
| Environmental | Pyroclastic flows burned forest and farmland on the upper slopes. Ash fell on land far from the volcano. Heavy rain then washed loose ash into rivers as lahars, which buried land and damaged bridges and homes. |
Strategies are the action plans. Techniques are the methods used.
| Strategy | Techniques |
|---|---|
| Monitoring and prediction | Indonesia's volcano agency (the Centre for Volcanology and Geological Hazard Mitigation) and its observatory in Yogyakarta watched Merapi all the time. They used seismometers for earthquakes and tremors, tiltmeters and GPS to measure the swelling of the summit, and gas measurements. Before the eruption they saw rising earthquake activity and swelling. |
| Alert levels and exclusion zones | A four-level alert system told people what to do. Level 4 ('Awas') was issued on 25 October, and the danger zone was widened in steps from 10 km to 15 km to 20 km as the eruption grew. |
| Hazard maps and evacuation plans | Maps showed which valleys and villages were at risk from pyroclastic flows and lahars. Villages had planned routes and shelters, and local people were educated about the risks. |
| Lahar dams | Check dams (called sabo dams) were built across river channels. They trap sediment and slow lahars, protecting towns and farmland downstream. |
Sustainable here means management that keeps people safe over the long term, at a cost the country can afford, while letting communities keep farming the fertile land.
| Strengths | Weaknesses |
|---|---|
| Good monitoring gave early warning. Estimates suggest that more than 10,000 lives were saved by the evacuations. Zones were widened in step with the activity. Lahar dams and hazard maps gave long-term protection. | More than 340 people still died, including some inside the danger zone. Some people ignored warnings or went back. Camps were crowded, and moving about 350,000 people was costly. Lahars kept threatening people for months. |
Judgement: monitoring was the most important strategy because it allowed a timely evacuation, which saved thousands of lives. The death toll could have been far higher. In an exam answer, give figures, named places and a balanced judgement.
Study the 2010 eruption of Mount Merapi in Indonesia.
(a) Identify the type of plate boundary on which Merapi lies. [1 mark]
(b) Explain why a strato-volcano such as Merapi erupts explosively. [2 marks]
(c) Describe two ways the eruption affected the economy. [2 marks]
(d) Evaluate how far the strategies and techniques used at Merapi managed the impacts of the eruption. [6 marks]
(a) A convergent (destructive) boundary (1).
(b) The lava is thick and sticky (1), so gas cannot escape and pressure builds up until it explodes (1).
(c) Farmland, crops and cattle were lost, so farmers lost income (1). Yogyakarta airport closed and many flights were cancelled because of the ash.
(d) Level 3 (5-6 marks): Indonesia used monitoring, alert levels, exclusion zones, hazard maps and lahar dams. Monitoring of earthquakes and swelling gave early warning, so about 350,000 people were evacuated and more than 10,000 lives were probably saved. The exclusion zone was widened from 10 km to 20 km as the eruption grew, which kept people away from the pyroclastic flows. Lahar dams helped to protect rivers such as the Code near Yogyakarta over the long term. However, more than 340 people still died, because some ignored warnings or were inside the zone, and camps were crowded and costly. Overall, management was largely successful because monitoring and evacuation saved thousands of lives, but it could not remove every risk. A Level 2 answer would describe the strategies and give one strength or weakness; a Level 1 answer would only list them.
For a six-mark evaluation, include a named place, a figure with 'about' or 'more than', a strength, a weakness and a final judgement.