OCR A-Level Geography Geographical debates (03), June 2025: Question 19
33 marks · Hard difficulty · Extended Response
Assess the extent to which explosive volcanic eruptions generate the most dangerous hazards.
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Question text
Topic 3.5 – Hazardous Earth
‘Explosive volcanic eruptions generate the most dangerous hazards.’
To what extent is this true? [33]
Mark scheme
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Question Answer Mark Guidance
‘Explosive volcanic eruptions generate the most 33 Indicative content AO1 – 9
dangerous hazards.’ To what extent is this true? AO1 x9 marks
AO2 x24 Demonstrating knowledge and understanding of hazards
AO1 generated by volcanic eruptions could potentially include:
Level 4 (7–9 marks) • Hazards generated by volcanic eruptions e.g. lava
Demonstrates comprehensive knowledge and understanding flows, pyroclastic flows, tephra, toxic gases, lahars,
of hazards generated by volcanic eruptions. floods, tsunamis.
• Types of volcanic eruptions e.g. explosive / effusive
Level 3 (5–6 marks) • Accept all hazards associated with tectonic activity
Demonstrates thorough knowledge and understanding of (seismic and volcanic).
hazards generated by volcanic eruptions.
AO2 – 24 marks
Level 2 (3–4 marks) Application of knowledge and understanding to analyse and
Demonstrates reasonable knowledge and understanding of evaluate the extent to which explosive volcanic eruptions
hazards generated by volcanic eruptions. generate the most dangerous hazards could potentially
include:
Level 1 (1–2 marks) • Expect range of ‘dangerous’ e.g. impact on people, over
Demonstrates basic knowledge and understanding of hazards time or different spatial scales
generated by volcanic eruptions. • Dangerous to what? Life, injuries, property, economic
activities, culture, political situation
0 marks • Yes – higher VEI scores with more pyroclastic flows
No response or no response worthy of credit. travelling longer distances (up to 20km from crater) and
faster than lava flows (500km/hr)
AO2 • Yes – danger over larger area e.g. Pinatubo impacts felt
Level 4 (19–24 marks) globally → ash carried around world affecting crops and
Demonstrates comprehensive application of knowledge and air temperatures. 1816 – ‘year without a summer’ in
understanding to provide a clear, developed and convincing northern hemisphere → Mt Tambora, Indonesia eruption
analysis that is fully accurate of how explosive volcanic 1815
eruptions generate the most dangerous hazards.
• Yes / no – large effusive eruptions e.g. E15 not
dangerous to human life but more damaging to economy
Demonstrates comprehensive application of knowledge and
→ interruption to movements of goods and people
understanding to provide a detailed and substantiated
• Yes / no – effusive eruptions on Hawaii affect large areas
evaluation that offers secure judgements leading to rational
of the island – agriculture, transport, housing
conclusions that are evidence based as to the extent to
which explosive volcanic eruptions generate the most • No - Lake Nyos poisonous gas hazard – very dangerous
dangerous hazards. as least understood and not predictable.
• Depends on factors such as level of economic resourcing
Relevant concepts are authoritatively discussed. in an area – AC / EDC / LIDC
• Seismic hazards – factors affecting level of danger, e.g.
Level 3 (13–18 marks) magnitude, preparedness, population density, wealth.
Mark Scheme June 2025
Demonstrates thorough application of knowledge and
understanding to provide a clear and developed analysis that 50
shows accuracy of how explosive volcanic eruptions generate
the most dangerous hazards.
Demonstrates thorough application of knowledge and
understanding to provide a detailed evaluation that offers
generally secure judgements, with some link between rational
conclusions as to the extent to which explosive volcanic
eruptions generate the most dangerous hazards.
Relevant concepts are discussed but this may lack some
authority.
Level 2 (7–12 marks)
Demonstrates reasonable application of knowledge and
understanding to provide a sound analysis that shows some
accuracy of how explosive volcanic eruptions generate the
most dangerous hazards.
Demonstrates reasonable application of knowledge and
understanding to provide a sound evaluation that offers
generalised judgements and conclusions, with limited use of
evidence as to the extent to which explosive volcanic
eruptions generate the most dangerous hazards.
Concepts are discussed but their use lacks precision.
Level 1 (1–6 marks)
Demonstrates basic application of knowledge and
understanding to provide a simple analysis that shows limited
accuracy of how explosive volcanic eruptions generate the
most dangerous hazards.
Demonstrates basic application of knowledge and
understanding to provide an un-supported evaluation that offers
simple conclusions as to the extent to which explosive volcanic
eruptions generate the most dangerous hazards.
Concepts are not discussed or are so inaccurately.
0 marks
Mark Scheme June 2025
No response or no response worthy of credit.
Quality of extended response
Level 4
There is a well-developed line of reasoning which is clear and
logically structured. The information presented is relevant and
substantiated.
Level 3
There is a line of reasoning presented with some structure. The
information presented is in the most-part relevant and
supported by some evidence.
Level 2
The information has some relevance and is presented with
limited structure. The information is supported by limited
evidence.
Level 1
The information is basic and communicated in an unstructured
way. The information is supported by limited evidence and the
relationship to the evidence may not be clear.
How to answer it
Topic 3.5 Hazardous Earth: Evaluating Volcanic Hazard Danger
This 33-mark evaluative essay assesses your ability to synthesize tectonic theory with empirical case study evidence under two core assessment objectives:
- AO1 (9 Marks): Depth and accuracy of knowledge regarding volcanic processes, eruption types (explosive vs effusive), characteristics of primary/secondary hazards (pyroclastic flows, lahars, tephra, ash clouds, lava flows, toxic gases), and comparative tectonic events (including seismic hazards).
- AO2 (24 Marks): Critical evaluation and balanced analysis of what constitutes "danger" (spatial footprint, loss of life, economic cost, disruption to aviation/food security) and whether danger is governed by eruption explosivity (VEI) or mediated by human factors (vulnerability, economic status: AC vs EDC vs LIDC, governance, preparedness).
Question 19* Analysis
‘Explosive volcanic eruptions generate the most dangerous hazards.’ To what extent is this true? [33 marks]
• AO1: 9 marks maximum (Level 4: 7–9 marks — Comprehensive, detailed knowledge)
• AO2: 24 marks maximum (Level 4: 19–24 marks — Fully developed, evidence-based, balanced evaluation reaching substantiated conclusions)
• * Quality of Extended Response: Assessed holistically on structure, clarity of logic, and geographic terminology.
1. Deconstructing the Question: Defining "Danger"
📐 Analytical Criteria: What is "Danger"?
Top-band answers unpack the word "danger" at the outset rather than treating it as a simple death toll:
- Morbidity & Mortality: Immediate threat to human life (e.g., speed and lethality of pyroclastic flows).
- Spatial Scale: Local (lava flows) vs regional (lahars/tephra) vs global (aerosols, climatic cooling, ash in the jet stream).
- Economic & Infrastructure: Farmland ruined, flight corridors closed, property buried.
- Temporal Scale: Immediate acute crisis vs long-term famine or displaced populations.
🧠 Essay Structure Blueprint
- Introduction: Define explosive (viscous, silicic magma, destructive margins, high VEI 4–8) vs effusive (basaltic, low viscosity, constructive/hotspot, VEI 0–2). Set up the multi-criteria definition of danger.
- Paragraph 1 (Agree): Explosive primary hazards kill instantly (Pyroclastic Density Currents at Mt St Helens / Mt Pinatubo; global climatic cooling like Tambora 1815).
- Paragraph 2 (Counter - Effusive Hazards): Basaltic eruptions cause catastrophic structural and economic devastation (Kilauea, Hawaii) or unique global economic paralysis (Eyjafjallajökull 2010).
- Paragraph 3 (Counter - Invisible/Atypical Volcanic Hazards): Toxic volcanic gas events (limnic eruption at Lake Nyos, Cameroon 1986 killed 1,700 with zero explosive pyroclastics).
- Paragraph 4 (Synoptic Counter - Hazard vs Vulnerability & Earthquakes): Are earthquakes far more dangerous than *any* volcanic hazard? (Haiti 2010 vs Merapi). Vulnerability determines disaster risk: Risk = (Hazard × Vulnerability) ÷ Capacity .
- Conclusion: Direct, substantiated verdict weighing scale, hazard type, and development context.
2. Evidence & Comparative Arguments
✅ Arguments Supporting the Statement (Explosive = Most Dangerous)
- Pyroclastic Flows (PDCs): Speeds exceeding 200–500 km/h and temperatures over 700°C leave zero evacuation window once initiated (e.g., Mt Pelée 1902 killed 30,000; Montserrat 1997 rendered 60% of the island uninhabitable).
- Global Climatic Hazard: Plinian columns inject SO₂ and aerosols into the stratosphere. Mt Tambora (1815, VEI 7) triggered the 1816 "Year Without a Summer," causing global agricultural collapse and tens of thousands of starvation deaths.
- Secondary Lahars: Heavy ash fall mixing with rainfall or glacial melt produces devastating lahars (e.g., Nevado del Ruiz 1985 buried Armero, killing >23,000).
💡 Arguments Challenging the Statement (Effusive, Other Hazards & Context)
- Effusive Economic Devastation: Eyjafjallajökull 2010 (VEI 4, phreatomagmatic/effusive characteristics) grounded transatlantic aviation, costing airline industry ~$1.7 billion USD without a single death.
- Persistent Lava Inundation: Kilauea (Hawaii, 2018) effusive fissure flows destroyed over 700 homes and displaced thousands; high financial asset loss despite negligible death toll.
- Silent Gas Disasters: Lake Nyos (1986), a limnic degassing event of magmatic CO₂, asphyxiated 1,746 people overnight—proving non-explosive events can be extraordinarily lethal.
- Earthquakes vs Volcanoes: Ground shaking, liquefaction, and tsunamis (e.g., Boxing Day Tsunami 2004, Haiti 2008/2010) generate casualties orders of magnitude higher than Holocene explosive volcanism due to lower predictability and sudden onset.
3. Direct Comparison Matrix for Top-Band (Level 4) AO2
| Eruption / Event | Type / Mechanism | Nature of Danger | Danger Verdict |
|---|---|---|---|
| Mt Pinatubo (1991) | Explosive (VEI 6, Dacitic) | PDCs, global SO₂ cooling (-0.5°C), massive typhoon-induced lahars. | High Global & Regional Danger: High death toll mitigated only by successful early monitoring/evacuation (USGS/PHIVOLCS). |
| Eyjafjallajökull (2010) | Explosive ash column under glacier | Silica-rich fine ash plumes drifting into European commercial flight corridors. | High Economic Danger: Zero direct human casualties, but severe global supply chain and GDP impact. |
| Kilauea, Hawaii (2018) | Effusive (Basaltic, Hotspot) | Fast-moving 'A'ā and Pāhoehoe lava flows, toxic vog (SO₂ gas). | High Spatial Property Danger: Little threat to human life due to slow flow paths, but complete permanent destruction of land and property. |
| Port-au-Prince, Haiti (2010) | Seismic (Conservative margin) | Magnitude 7.0 Mw ground shaking, building collapse, disease outbreak. | Absolute Danger: >220,000 fatalities, illustrating that seismic hazards frequently exceed volcanic events in lethality. |
4. Examiner Guidance: How to Secure Level 4 Marks
❌ Common Errors that Cap Marks
- One-sided narrative: Simply listing dangerous explosive volcanoes without comparing them to effusive eruptions, toxic gases, or seismic events.
- Equating "danger" solely with deaths: Ignoring infrastructural wipeout, global air travel shutdown, and food security impacts.
- Ignoring human vulnerability: Forgetting that an explosive eruption in an unpopulated zone (e.g., Novarupta 1912) creates minimal risk, whereas moderate eruptions near dense populations in LIDCs/EDCs (e.g., Mt Merapi, Indonesia) are catastrophically dangerous.
- Vague case details: Stating "ash went everywhere" instead of referencing tephra depths, flight bans, or specific spatial radii.
🧠 What Distinguishes Top-Level (29–33 Mark) Scripts
- Continuous Evaluation: Using evaluative discourse markers throughout ("However, danger cannot be measured in raw energy alone...", "While explosive eruptions present unmatched acute mortality risks, effusive eruptions...").
- Clear Magma Mechanics: Accurately linking high viscosity, high silica content (andesitic/rhyolitic), and trapped gases to violent explosive hazards (PDCs, tephra plumes).
- Nuanced Conclusion: Concluding that while explosive eruptions generate the greatest potential for catastrophic global disruption and rapid loss of life, the actualized danger is heavily controlled by population density, governance, monitoring, and level of economic development (AC vs LIDC).
Topics
Topic 3.5 Hazardous Earth · 2.a. There is a variety of volcanic activity and resultant landforms and landscapes. · 2.b. Volcanic eruptions generate distinctive hazards. · 3.b. Earthquakes generate distinctive hazards.
Question and mark scheme from the OCR A-Level Geography examination, Geographical debates (03), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.