Mount Merapi's 2010 eruption: hazards, response and risk management
A sourced StudyForA example of the October–November 2010 Merapi eruption in Indonesia. Confirm that your centre selected this volcano before using it as your required example.
Section CASE-EXAMPLES · Centre-selected detailed specific examples
Exam scope and assessment notes
Cambridge IGCSE (9–1) Geography 0976, 2027–2029 syllabus, Topic 4.4.4. The syllabus does not prescribe one universal set of named detailed specific examples: centres select places suited to their learners. Sixteen optional StudyForA evidence packs now cover all sixteen example objectives, but the centre's choices are unconfirmed. Match each pack to your centre's chosen place and replace any mismatch before treating the course as complete. Original StudyForA explanations and self-check practice are not Cambridge papers, official grades or teacher-marked coursework. Map, graph and written answers are not automatically assessed. Paper 4 practice uses supplied or invented data and cannot certify safe fieldwork, equipment use or real data collection. Centre-set coursework and specialist teacher review remain pending. This is the separate 9–1 qualification. Cambridge limits this 9–1 syllabus to certain zones: in June it is available in Administrative Zone 3 and for centres in Oman and the UAE; in November it is available in Zone 3 only. Confirm the exam series and entry with your centre. Cambridge also says an entry cannot be switched from 9–1 to A*–G after the entries deadline.
Before you begin
- No previous Geography course is assumed. Use the supplied map, data or scenario; distinguish observation from explanation and support conclusions with evidence.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Why did CVGHM extend the Merapi evacuation zone to 20 km in November 2010?
What you will learn
- Explain the monitoring signs before Merapi's 2010 eruption
- Describe primary and secondary hazards and their impacts
- Use evidence about warning, evacuation and shelter
- Evaluate the limits of forecasting and long-term volcanic-risk management
Escalating signals preceded a major eruption
Mount Merapi is an active volcano in Central Java, Indonesia, close to densely settled areas. In October 2010, Indonesian scientists detected earthquakes, gas emissions and ground movement above the volcano's usual levels. Satellite radar tracked rapid lava-dome growth through cloud. On 26 October, the first explosive phase sent pyroclastic flows as far as 8 km; stronger explosions followed on 4–5 November. USGS described the sequence as Merapi's largest eruption in more than a century.
A lava dome can collapse and produce fast, hot pyroclastic flows of ash and rock. Merapi's eruption also left deposits that later rains remobilised as lahars down river valleys. These hazards differ in timing: pyroclastic flows can arrive during the eruption with little time to escape, while lahars can remain a danger after the main explosive phase.
People and livelihoods faced immediate and continuing impacts
USGS reported 341 deaths, more than 2,000 houses destroyed and nearly 350,000 people evacuated. Pyroclastic flows reached 15 km from the summit, damaging settlements and farmland; ash disrupted transport and flights. Heavy rain later generated lahars, and thousands more people had to flee in January 2011. Fatality totals in early reports vary as records were revised, so this pack uses the stated USGS figure and date rather than combining estimates.
Evacuation reduced exposure but displaced people from homes, work and services. Some residents did not want to leave land, livestock or livelihoods; risk communication and accessible shelters were therefore part of the response, not just scientific monitoring.
Monitoring informed expanding evacuation zones
Indonesia's Center for Volcanology and Geological Hazard Mitigation (CVGHM), supported by the USGS Volcano Disaster Assistance Program, interpreted seismicity, gas, ground movement and satellite radar. Authorities first evacuated people within 10 km. On 4 November, stronger warning signs led CVGHM to extend the evacuation zone to 20 km, just hours before the largest flows travelled as far as 15 km. More than 700 evacuation centres supported people who left. USGS estimates the timely warnings and evacuations saved between 10,000 and 20,000 lives; this is an estimate, not a directly counted total.
Long-term risk management also needs updated hazard zones, public warnings, evacuation routes, shelter capacity, local drills and plans for rain-triggered lahars. Evacuation boundaries must change when monitoring shows that hazards could travel farther than earlier estimates. Forecasts reduce risk when agencies can communicate clearly and people can reach safe places.
Judge the response without treating it as perfect prediction
The warning was successful because monitoring signals intensified and officials acted conservatively. It did not predict the eruption's exact size or remove all loss: 341 people died and lahars continued after the explosive phase. A sound evaluation recognises both the lives protected and the costs of displacement, the limits of forecasts and the need for long-term preparedness.
Sources for this lesson
Pause and explain
What does the estimate that evacuation saved 10,000–20,000 lives represent?
Worked example
Merapi's evacuation boundary expanded from 10 km to 20 km. Explain how this change related to the observed hazard and why the 15 km flow distance does not make a 15 km boundary automatically safe.
Show the worked solution
- The zone was expanded after stronger seismic and satellite evidence suggested a larger eruption was possible.
- Flows travelled as far as 15 km in this event, but future conditions and uncertainty can differ.
- Evacuation decisions include safety margins, route access, timing and lahar risk after the eruption.
Answer Authorities expanded the zone from 10 km to 20 km when seismicity and satellite observations indicated a larger event could occur. Although the longest reported flows travelled about 15 km, that distance is not a guaranteed limit for future flows. A 20 km boundary added a safety margin and also had to account for uncertainty, evacuation time and later lahars.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Describe two monitoring signs before the 2010 Merapi eruption and explain how they informed an evacuation decision.
Give me a hint
Name observable signals and connect them to the danger of a larger eruption.
Compare my reasoning
- Indonesian scientists observed stronger earthquakes, gas emissions and ground movement from 22 October.
- Satellite radar tracked rapid lava-dome growth through cloud.
- After increased seismicity and remote-sensing evidence, CVGHM extended the evacuation zone to 20 km on 4 November.
Higher seismicity, gas emissions, ground movement and rapid dome growth indicated an unusually active volcano. Satellite radar helped scientists track the dome despite cloud. CVGHM used the combined evidence to extend the evacuation zone to 20 km before the largest flows travelled as far as 15 km.
Look for these in your work
- Two monitoring signals accurately identified
- Evidence linked to a decision
- Timing and distance retained
Use Merapi evidence to explain one primary impact, one secondary impact and one response.
Give me a hint
Separate the pyroclastic flow during the eruption from later rain-triggered lahars.
Compare my reasoning
- Pyroclastic flows reached up to 15 km and destroyed homes; USGS reports 341 deaths.
- Rain later remobilised deposits as lahars, forcing additional people to flee in January 2011.
- More than 700 evacuation centres supported people moved from danger zones.
The eruption's pyroclastic flows destroyed homes and caused 341 deaths according to USGS. Heavy rain later produced lahars and forced further displacement. Authorities organised evacuation centres and expanded the danger zone as monitoring showed that flows might reach farther than first expected.
Look for these in your work
- Primary and secondary hazards distinguished
- Impact evidence attributed
- Response linked to exposure reduction
Evaluate how well the 2010 warning and evacuation system managed risk at Merapi.
Give me a hint
Balance lives protected against remaining deaths, displacement, forecast uncertainty and post-eruption hazards.
Compare my reasoning
- Monitoring and satellite radar helped Indonesian scientists identify a larger-than-usual eruption and extend the evacuation zone from 10 to 20 km.
- More than 700 centres supported evacuation; USGS estimates 10,000–20,000 lives were saved.
- Despite the response, 341 people died, people lost homes and livelihoods, and rain-triggered lahars continued.
- Effective future planning needs accessible warning, routes, shelters, drills and lahar plans as well as monitoring.
The response was effective in reducing exposure: monitoring and satellite radar informed an expanded 20 km evacuation zone, and USGS estimates that 10,000–20,000 lives were saved. But the estimate is not a direct count, 341 people still died and lahars caused further disruption. Risk management therefore needs accessible evacuation and shelter plans and continued lahar warnings, not monitoring alone.
Look for these in your work
- Effectiveness supported with evidence
- Limits and ongoing hazards recognised
- Practical improvements recommended
Common mistakes
- Treating all volcanic hazards as equally fast or equally widespread
- Assuming a 15 km observed flow is the maximum distance a future flow could reach
- Describing an evacuation estimate of saved lives as a counted total
- Ignoring lahars after the explosive phase
- Claiming no one died because the evacuation worked
- Treating warning as useful when routes and shelters are inaccessible
- Using this optional pack without checking your centre's selected volcano
What can you explain now?
Which hazard can continue after an eruption when rain remobilises volcanic deposits?
Compare with the explanation
A lahar
Ash and rock deposits can mix with water and move down river valleys as lahars.
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Make it stick
Name two monitoring signs, one primary hazard, one later hazard and one dated impact or response figure for Merapi in 2010.
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