HookIn 2010 two earthquakes struck weeks apart. One killed 500; the other killed 220,000
On 12 January 2010 a magnitude 7.0 earthquake struck near Port-au-Prince, Haiti, and killed an estimated 220,000 people. Six weeks later, on 27 February, a magnitude 8.8 earthquake struck off the coast of Chile — a quake that released roughly 500 times more energy — and killed around 500. The larger event, by every physical measure, produced a tiny fraction of the deaths. Read that pairing slowly, because it dismantles the single most common misconception in this unit: that the size of the natural event determines the scale of the disaster.
It does not. Chile had enforced seismic building codes, wealth, a functioning state and disaster planning; Haiti had unreinforced concrete, deep poverty, weak governance and no capacity to respond. The disaster is not the hazard — it is the collision of a hazard with human vulnerability, minus a society's capacity to cope. That relationship, often written as Risk = (Hazard × Vulnerability) ÷ Capacity to cope, is the spine of the entire topic. Every question here — volcanic, seismic, storm or wildfire — is asking you to separate the physical event from the human outcome, and to explain why the same magnitude produces catastrophe in one place and inconvenience in another.
ModelThe disaster is the vulnerability, not the hazard
AQA opens the unit with the concept of hazard itself. A natural hazard is a natural process or event that threatens people and property; it becomes a disaster only when it causes serious harm that overwhelms a community's ability to cope. The gap between the two is vulnerability (exposure and susceptibility) and capacity to cope (wealth, governance, preparedness, technology). This is why the risk equation matters more than any single statistic: a huge hazard in a well-prepared, wealthy place can be low-risk, while a modest hazard in a poor, exposed place can be catastrophic.
How people respond depends on hazard perception, which is shaped by wealth, education, past experience, religion and value systems. Responses run along a spectrum from fatalism (acceptance, often religious) through adaptation and mitigation to active management, prediction and prevention. Two models organise this. Park's disaster-response curve plots quality of life over time through the stages of relief, rehabilitation and reconstruction, and its shape — how deep the dip and how fast the recovery — reveals a country's resilience. The hazard management cycle (mitigation, preparedness, response, recovery) frames it as a continuous loop rather than a one-off reaction. Deploying these frameworks, rather than just narrating events, is what lifts an answer into the higher AO2 bands.
Read the Haiti and Chile 2010 pairing through the risk equation. The hazard was larger in Chile (magnitude 8.8 versus 7.0). But Haiti's vulnerability was extreme — dense, informally-built Port-au-Prince, unreinforced masonry, a shallow focus almost beneath the capital — while its capacity to cope was minimal (a low-income economy, weak institutions, a collapsed government including the presidential palace). Chile inverted every term: lower vulnerability through strict seismic codes, higher capacity through wealth and planning. Risk = (Hazard × Vulnerability) ÷ Capacity to cope therefore predicts exactly what happened — the smaller hazard produced roughly four hundred times the death toll — and on Park's curve Haiti's line plunges far deeper and recovers far more slowly. That is a full evaluative paragraph built from one framework.
MechanismPlate tectonics: the engine underneath
The distribution of earthquakes and volcanoes is explained by plate tectonic theory. The Earth's rigid lithosphere is broken into plates that move over the weaker asthenosphere, driven by ridge push at spreading centres and, more importantly, slab pull as dense subducting plates sink, with mantle convection completing the picture. Evidence came from sea-floor spreading and palaeomagnetism — the symmetrical magnetic stripes either side of mid-ocean ridges recording reversals of Earth's magnetic field as new crust formed.
The hazards cluster at plate margins. At constructive (divergent) margins plates pull apart and magma rises, giving gentle effusive volcanoes and shallow, low-magnitude earthquakes (Iceland on the Mid-Atlantic Ridge). At destructive (convergent) margins one plate subducts beneath another, producing the most violent explosive volcanoes and the largest earthquakes, including tsunami-generating megathrust events (the Pacific 'Ring of Fire', the Andes, Japan). At conservative (transform) margins plates slide past one another, generating powerful earthquakes but no volcanism (the San Andreas Fault). Magma plumes or hot spots produce volcanoes far from any margin, such as Hawaii. Matching a hazard's character to its margin type is a reliable AO1 foundation for the whole section.
MechanismVolcanic hazards: form, magnitude and response
Volcanic hazards take several forms, and their danger depends on the magma type. Effusive basaltic volcanoes produce mostly lava flows — destructive to property but usually slow enough to escape. Explosive volcanoes at destructive margins produce the killers: fast, superheated pyroclastic flows, ash and tephra falls that collapse roofs and ground aircraft, toxic gases, and lahars — volcanic mudflows of ash mixed with water or meltwater that can bury towns hours after an eruption. In Iceland, sub-glacial eruptions add jökulhlaups, sudden glacial meltwater floods.
Magnitude is measured on the Volcanic Explosivity Index (VEI), a logarithmic scale from 0 to 8 based mainly on the volume of ejected material — each step up represents roughly a tenfold increase. The 1991 eruption of Mount Pinatubo in the Philippines reached VEI 6 and injected enough sulphate aerosol into the stratosphere to cool global temperatures by about half a degree Celsius for a year — a reminder that volcanic impacts can be secondary and global as well as primary and local. Responses divide into short-term (evacuation, exclusion zones, emergency relief) and long-term (monitoring seismicity and ground deformation, hazard mapping, land-use planning, rebuilding). Successful evacuation before Pinatubo, informed by monitoring, saved tens of thousands of lives — prediction turning a potential catastrophe into a managed emergency.
MechanismSeismic hazards: why magnitude and death toll diverge
Earthquakes result from the sudden release of built-up strain along faults, usually at plate margins. The primary hazard is ground shaking, but the secondary hazards frequently do the most damage: liquefaction (saturated, loose sediment temporarily behaving as a liquid, so buildings sink or tilt), landslides, and — where the seabed is displaced — tsunamis. Magnitude is measured on the moment magnitude scale (which has largely replaced the older Richter scale for large events), while the Mercalli scale records intensity of felt shaking and damage at a place. Crucially, magnitude scales are logarithmic: each whole number is about ten times the ground-shaking amplitude and roughly 31.6 times the energy release.
That logarithmic jump, combined with vulnerability, explains the Haiti–Chile paradox. Responses to seismic risk rest on the three Ps — prediction (still unreliable for timing, so reliance falls on probabilistic hazard mapping), protection (aseismic building design, retrofitting, and tsunami defences and warning systems), and preparation (drills, education, emergency planning). Because timing cannot be forecast, engineering and preparedness — not prediction — save the most lives, which is exactly why Chile's enforced building codes mattered more than any warning could have.
Prove the divergence with the magnitude maths. Energy released rises by a factor of about 31.6 for every one-point rise in moment magnitude, so the ratio between Chile's 8.8 and Haiti's 7.0 is 31.6^(8.8 − 7.0) = 31.6^1.8. Working the exponent as powers of ten, 31.6 ≈ 10^1.5, so 31.6^1.8 = 10^(1.5 × 1.8) = 10^2.7 ≈ 500. Chile's earthquake therefore released roughly 500 times the energy of Haiti's, yet killed roughly one four-hundredth as many people. State the calculation, then the interpretation: since the physically far larger event was far less deadly, the death toll must be governed by vulnerability and capacity to cope — enforced seismic codes, wealth and governance — not by magnitude. That is AO3 skill feeding a decisive AO2 judgement.
MechanismStorm hazards and fires in nature
Tropical cyclones (hurricanes, typhoons) form only under specific conditions: sea-surface temperatures of at least about 26.5°C to a depth of roughly 50 m, latitudes between about 5° and 20° where the Coriolis effect can spin the system, low vertical wind shear, and an unstable, humid atmosphere. Their hazards are high winds, torrential rain and inland flooding, landslides, and — the biggest killer — storm surge, the dome of seawater driven ashore by low pressure and wind. Magnitude is measured on the five-step Saffir–Simpson scale, with Category 5 beginning at sustained winds of 157 mph (252 km/h). Responses span prediction (satellite tracking and warnings), protection (sea walls, cyclone shelters, building codes) and preparation (evacuation planning and education).
Fires in nature — wildfires — depend on the interaction of fuel, weather and ignition. Intense fires are favoured by abundant, dry fuel (oil-rich vegetation such as eucalyptus or chaparral), a climate with a dry season, recent weather that is hot, droughted and windy, and fire behaviour that can escalate from ground to surface to crown fires. Causes are both natural (lightning) and human (arson, discarded cigarettes, power lines, land clearance). Australia's 2019–20 Black Summer bushfires burned roughly 18.6 million hectares, destroyed thousands of homes and were estimated to have killed or displaced around three billion animals — a hazard whose scale was amplified by record drought and heat, illustrating the same principle as every other hazard here: physical conditions set the potential, but exposure and preparedness set the outcome.
CaseThe Philippines, Haiyan and the twin quakes
AQA requires a multi-hazardous environment beyond the UK and a local-scale study of a place recently affected by a hazard. The Philippines is the model multi-hazard environment: it sits on the Pacific Ring of Fire, so the subducting Philippine Sea Plate generates frequent earthquakes and active volcanoes (Pinatubo, Taal, Mayon), while its western Pacific location exposes it to around twenty tropical cyclones a year. The same population is therefore squeezed by overlapping tectonic and atmospheric hazards, and poverty in exposed coastal and informal settlements multiplies the vulnerability across all of them.
For recent events, two contrasts do the analytical work. Typhoon Haiyan (Yolanda) struck the Philippines in November 2013 as a Category 5 storm; a storm surge of up to around five to seven metres devastated Tacloban and the death toll reached roughly 6,300 — a low-capacity, high-vulnerability outcome that maps directly onto Park's curve and the risk equation. Set it against a high-income storm response, or set the Haiti (2010, magnitude 7.0, about 220,000 deaths) and Chile (2010, magnitude 8.8, about 500 deaths) earthquakes side by side, and the pattern is consistent: development level, governance and preparedness — not the physical magnitude — decide whether a hazard becomes a disaster. Naming the events, dates, magnitudes and death tolls, then explaining the divergence through vulnerability and capacity, is the difference between a Level 2 and a Level 4 response.
VocabularyKey terms the mark scheme pays for
TrapsMisconceptions that cost marks
ExamWhat examiners want
AQA marks Hazards against AO1 (the tectonic theory, hazard forms, magnitude scales and models), AO2 (applying and evaluating them, above all on the 9- and 20-mark items) and AO3 (interpreting maps, graphs and hazard data). On resource questions, quote the figure and convert it into meaning — a Saffir–Simpson category, a VEI value, a death-toll contrast — because credit is for geographical inference, not description. Where numbers appear, be ready to reason with a logarithmic scale: showing that a one-point magnitude difference is a roughly thirty-fold energy difference is a high-value AO3 move.
The extended essays reward frameworks over narrative. Structure evaluative answers around the risk equation, Park's curve or the hazard management cycle, and drive every judgement back to the question's command word — 'Assess', 'Evaluate' and 'To what extent' all demand a sustained, evidenced argument with a substantiated conclusion, which the top mark-scheme level requires. The single most reliable line of reasoning on this topic is that the level of development, governance and preparedness — not the physical magnitude — determines whether a hazard becomes a disaster; prove it with paired, named, dated case studies (Haiti versus Chile 2010, Typhoon Haiyan, the Philippines) and quantified detail rather than assertion.