Interpret global geophysical disaster trends and projections, and evaluate adaptation, pre-event and post-event strategies for earthquakes, tsunamis, volcanoes and mass movements, using Grindavík and other named examples.
Each is in the Geography glossary, with every other term in the subject.
A stage in a scale of warnings, often numbered or coloured, that tells authorities and the public how active a volcano or other hazard is and what actions, such as evacuation, to take.
The design of buildings and infrastructure so that they bend, absorb or isolate earthquake shaking without collapsing, for example through flexible frames, cross-bracing, shear walls, dampers and base isolation.
A method of aseismic design in which a building rests on flexible bearings, such as layers of rubber and steel, that absorb ground motion so that less shaking reaches the structure above.
An approach to recovery that uses reconstruction to reduce future disaster risk, for example by rebuilding to stronger codes, moving homes out of hazard zones and improving services.
A bond sold to investors that pays a government or insurer a set sum if a defined disaster, such as an earthquake above a given magnitude in a given area, occurs; otherwise investors keep their money and interest.
An approach in which local people identify the hazards they face and plan, carry out and monitor their own risk reduction actions, often with support from governments and NGOs.
Mapping in which many volunteers add data, such as roads, buildings or damage seen on satellite images or reported by phone, to a shared online map used by responders.
Describe global trends in geophysical hazard events, disasters, deaths and economic losses, and explain why they differ.
Evaluate the reliability of disaster databases such as EM-DAT.
Explain how population growth and urbanisation are likely to change exposure to geophysical hazards in the future.
Distinguish between hazard adaptation and hazard mitigation, and between government planning and personal resilience.
Evaluate land-use zoning, building codes, preparedness, insurance and new technology as ways of adapting to geophysical hazards.
Explain pre-event management strategies for mass movements, earthquakes, tsunamis and volcanoes.
Analyse a GPS deformation time series and other monitoring data.
Evaluate post-event management (rescue, rehabilitation, reconstruction) using the disaster response curve.
Examine how communications technologies are used to map disasters, locate survivors and support continuing human development.
No technology can prevent an earthquake or a volcanic eruption. What societies can change is how many people are exposed, how vulnerable they are and how quickly they recover. Future resilience, the capacity to absorb a hazard event, recover from it and adapt, depends on decisions about planning, buildings, monitoring and response made before and after each event.
The key concept of possibility is central to future resilience. Future losses depend on how fast cities grow into hazard zones and on which management strategies are chosen. Power matters too, because governments, insurers, engineers and communities decide which strategies are funded and who benefits from them.
62 exam-style questions on this subtopic, written in the style of the IB papers. The first has its markscheme open. Counted on
Evaluate the role of flood warning technology in reducing flood risk in countries at different levels of economic development.
10 marks
Marks should be allocated according to the markbands.
Flood warning technology includes river gauges with telemetry, rainfall radar, satellite observation, hydrological and hydraulic models, forecasting systems and the means of sending warnings (sirens, mobile phone alerts, apps, radio and television, community networks). Flood risk depends on the hazard and on the exposure and vulnerability of people. Warnings cannot stop a flood but can reduce its impacts. Answers should consider countries at different levels of economic development, which may be high-, middle- or low-income.
Possible applied themes (AO2) demonstrating knowledge and understanding (AO1):
High-income countries: dense gauge networks, radar and model-based forecasts; tiered warning systems (eg the UK Environment Agency's flood alert, flood warning and severe flood warning, sent by phone, text and email); continental systems such as the European Flood Awareness System (EFAS).
Warnings allow property-level protection to be put in place, defences and barriers to be operated and people to evacuate, reducing losses.
Failures in high-income countries: July 2021, Ahr valley in Germany, where forecasts were available days ahead but local warnings and evacuation were too late; more than 180 people died in Germany.
Lower-income countries: Bangladesh's Flood Forecasting and Warning Centre and its cyclone and flood shelters, plus volunteer networks, have helped cut deaths; newer satellite and AI-based forecasts can extend lead times where gauges are scarce.
Low-technology systems (community flood monitors, flags, megaphones, mosque loudspeakers) may be effective where mobile coverage or trust in authorities is limited.
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A model, devised by Park in 1991, that shows how quality of life falls during a hazard event and recovers through the phases of relief, rehabilitation and reconstruction.
The policies and actions that aim to prevent new disaster risk, reduce existing risk and manage what remains, so that losses of life, livelihoods and assets are reduced.
The change over time in the number of recorded disasters, the deaths they cause, the people affected or their economic losses, usually shown by year or by decade.
A system that detects the first, faster seismic waves of an earthquake and sends automatic alerts that arrive seconds to tens of seconds before the strongest shaking reaches more distant places.
The Emergency Events Database, a global record of disasters since 1900 kept by the Centre for Research on the Epidemiology of Disasters in Belgium, which lists events that meet set thresholds for deaths, people affected or calls for help.
The use of fixed satellite navigation (GNSS) receivers on a volcano or fault to measure ground movement of a few millimetres, such as the uplift caused by magma collecting below.
Adjusting land use, buildings, behaviour and institutions so that people can live with a hazard and suffer less harm from it, without trying to stop the hazard itself.
Interferometric synthetic aperture radar: a satellite technique that compares radar images taken at different times to map ground uplift or subsidence of a few millimetres over large areas.
Changing the path of a lava flow away from settlements and infrastructure by building earth barriers or channels, or by cooling the flow front with water.
The capacity of individuals and households to prepare for, cope with and recover from a hazard event, for example through emergency plans, savings, insurance and knowledge of what to do.
The actions taken after a hazard event to save lives, meet urgent needs and restore and improve communities, usually divided into rescue, rehabilitation and reconstruction.
The measures taken before a hazard event to reduce its impact, including monitoring, warnings, land-use planning, building design, defences, education and evacuation plans.
The long-term phase of post-event management, lasting months to years, in which buildings, infrastructure and the economy are rebuilt, ideally to a safer standard than before.
The phase of post-event management, lasting weeks to months, in which temporary housing is provided and basic services, infrastructure and livelihoods are restored.
The emergency provision of food, water, shelter, medical care and other essentials to people affected by a disaster, mainly during the rescue phase.
The first phase of post-event management, lasting hours to days, in which survivors are found and freed, the injured are treated and urgent needs for shelter, water and food are met.
A wall built at the foot of or across a slope to hold back soil or rock and prevent it from sliding, often with drains to let water out from behind it.
A steel rod drilled and fixed deep into a rock face or slope to tie loose surface rock or soil to stable material underneath; a soil nail does the same in soil.
A dam built across a valley on a volcano or mountain slope to trap the boulders and sediment carried by lahars and debris flows while letting water pass through.
Strengthening an existing building or structure so that it can better withstand earthquakes, for example by adding steel bracing, concrete jackets around columns or shear walls.
A United Nations agreement adopted in Sendai, Japan, in 2015 that sets seven global targets and four priorities for reducing disaster deaths, people affected and losses between 2015 and 2030.
Engineering and vegetation measures that increase the shear strength of a slope or reduce the shear stress on it, such as drainage, regrading, retaining walls, rock bolts and planting.
An instrument that measures very small changes in the slope of the ground, used on volcanoes to detect swelling as magma rises and deflation after it erupts or drains.
A structure built to reduce the height or force of tsunami waves reaching the land, such as a seawall, breakwater or embankment, or a natural barrier such as a coastal forest or mangroves.
A network of seismometers, sea-level gauges and deep-ocean pressure sensors linked to warning centres that detect a possible tsunami and send alerts to coastal populations.
The specialised location, extraction and first medical care of people trapped in collapsed buildings, carried out by trained teams with equipment such as listening devices, cameras and cutting tools.
Escaping a tsunami by climbing to the upper floors or roof of a strong, tall building or a purpose-built tower or mound, used where high ground is too far away to reach in time.
The continuous measurement of a volcano's earthquakes, ground deformation, gas emissions and temperature to detect rising magma and forecast eruptions.
A disaster trend describes how the number of disasters, the deaths they cause, the people affected or their economic losses change over time. Trends for geophysical disasters behave differently from trends for the events themselves, and separating the two is the first step in interpreting them.
Most global disaster statistics come from EM-DAT, the Emergency Events Database, kept by the Centre for Research on the Epidemiology of Disasters (CRED) at the University of Louvain in Belgium. An event is entered if it kills at least 10 people, affects at least 100 people, or leads to a declared state of emergency or a call for international help.
The number of earthquakes and eruptions has no clear long-term trend. About 15 earthquakes of magnitude 7 or more occur in a typical year, and this rate has stayed broadly stable throughout the instrumental record, because plate motion does not change on human timescales. The number of recorded geophysical disasters, however, rose steeply from the 1960s to the 2000s.
Three reasons explain the rise. First, reporting improved: satellite communications, television and the internet mean that events in remote places are now recorded. Second, more people live in hazard zones, so more events affect enough people to pass the thresholds. Third, more countries ask for international help, which also qualifies an event for inclusion. The levelling off in the 2010s may reflect better building and warning in some countries, but the data are too short to be sure.
Deaths from geophysical disasters show no steady trend. A few catastrophic events dominate each decade: the 2004 earthquake and tsunami killed about 228,000 people, and the 2010 Haiti earthquake about 222,000 in EM-DAT’s count, so a single event can make one decade look far worse than the next. When measured as deaths per event, or per million people exposed, many countries show a clear fall as building standards, warnings and emergency services improve.
Economic losses, by contrast, have risen strongly. Cities in hazard zones contain more valuable buildings, infrastructure and businesses than ever before, so the same shaking destroys more money’s worth of assets. Losses are largest in absolute terms in HICs such as Japan and the United States, but largest relative to GDP in poorer and smaller economies.
The future risk of geophysical disasters depends more on the growth of population and cities than on changes in the hazards themselves. The United Nations projects that the world’s population will grow from about 8.2 billion in 2024 to about 9.7 billion in 2050, peaking at about 10.3 billion in the 2080s. Most of the growth will be in cities in Africa and Asia, many of them in hazard zones.
Many of the world’s largest cities lie on or near active faults or volcanoes: Tokyo, Istanbul, Tehran, Lima, Manila, Jakarta and Mexico City are all megacities or close to that size. As cities grow, informal settlements spread onto steep hillsides that are prone to landslides, as in Freetown, La Paz and Rio de Janeiro. The number of people exposed to a large earthquake or landslide is therefore likely to rise even if the hazards do not change.
Global climate change adds to future risk for mass movements in particular. More intense rainfall increases the number of rainfall-triggered landslides, and the thawing of permafrost and the retreat of glaciers destabilise mountain slopes. In May 2025 the collapse of the Birch Glacier in Switzerland buried most of the village of Blatten, after monitoring had led to the evacuation of its roughly 300 residents nine days earlier.
Governments have agreed global targets for disaster risk reduction, the policies and actions that prevent new risk, reduce existing risk and manage what remains. The Sendai Framework for Disaster Risk Reduction 2015–2030, adopted by United Nations member states in Sendai, Japan, in March 2015, replaced the earlier Hyogo Framework for Action (2005–2015).
The Sendai Framework is the main global agreement on disaster risk reduction.
Sendai Framework | Content |
|---|---|
Four priorities | 1. Understanding disaster risk. 2. Strengthening disaster risk governance. 3. Investing in disaster risk reduction for resilience. 4. Enhancing preparedness for response, and to "build back better" in recovery and reconstruction. |
Seven targets for 2030 | Substantially reduce disaster deaths and the number of people affected (per 100,000, compared with 2005–2015); reduce direct economic losses relative to global GDP; reduce damage to critical infrastructure such as schools and hospitals; increase the number of countries with national and local strategies; increase international cooperation with poorer countries; increase access to multi-hazard early warning systems. |
The framework marks a shift from responding to disasters towards reducing risk before they happen. Its targets are not legally binding, and progress depends on national governments and their budgets; large events such as the 2023 Türkiye–Syria earthquakes show how far some countries remain from them.
Because geophysical hazards cannot be stopped, most strategies aim to reduce their impacts by adapting where and how people live. Hazard adaptation describes these adjustments.
Land-use zoning keeps buildings away from the most dangerous land. It begins with hazard mapping: faults, lahar paths, lava flow routes, tsunami inundation zones and unstable slopes are mapped, and planning rules then restrict what may be built in each zone.
California’s Alquist-Priolo Earthquake Fault Zoning Act (1972), passed after the 1971 San Fernando earthquake, maps zones along active faults and prohibits most new homes from being built across them.
New Zealand sets fault avoidance zones in which building is limited, and after the 2010–2011 Christchurch earthquakes the government created a residential "red zone" where liquefaction had made land unfit to rebuild. The Crown bought and cleared more than 8,000 properties, and about 98% of owners accepted the offers.
Volcanic exclusion zones keep people out of the areas most likely to be hit by pyroclastic flows and lahars, as on the slopes of Merapi in Indonesia and Soufrière Hills in Montserrat.
Zoning is cheap compared with engineering, and it prevents losses permanently. Its limitations are political and social: land in hazard zones is often valuable or already built on, landowners resist restrictions, and poor households may have nowhere else to live. Managed relocation, as in Christchurch, is expensive and breaks up communities, and the full offers in Christchurch were made only to insured owners, while uninsured owners and owners of vacant land were first offered half the value, which critics saw as unfair.
Building codes set minimum standards for how buildings resist shaking, and their enforcement matters as much as their content. Chile, which has strict seismic codes, lost 525 people in an Mw 8.8 earthquake in February 2010, one of the largest earthquakes ever recorded; much of the damage on the coast came from the tsunami rather than from shaking. Codes protect new buildings only, so older buildings need strengthening, which is slower and costly.
Emergency plans and drills prepare whole populations. Japan holds its national Disaster Prevention Day each year on 1 September, the anniversary of the 1923 Great Kantō earthquake, and schools practise evacuations regularly. The "ShakeOut" drills begun in California, in which millions of people practise "drop, cover and hold on" at the same moment, have spread to many other countries.
Government planning leaves some risk with every household. Personal resilience describes what individuals and households do to prepare, cope and recover.
Personal preparedness includes an emergency kit, a family plan and meeting place, secured heavy furniture and water heaters, and knowledge of evacuation routes. Its cost is low, but it depends on awareness, which fades between events, and on money and space that the poorest households lack.
Insurance spreads the cost of losses across many policyholders and over time, so that households and businesses can rebuild quickly. Its use varies widely. New Zealand has a national public scheme that covers residential earthquake damage for homes with fire insurance, so insurers paid most of the costs of the 2016 Kaikōura earthquake. In California, by contrast, earthquake cover is sold separately and only a minority of homeowners buy it, and standard US home insurance does not cover land movement at all, as owners at Portuguese Bend found. In most LICs, very few households are insured.
Governments also insure themselves. A catastrophe bond transfers the risk of a defined disaster to investors, and regional pools such as the Caribbean Catastrophe Risk Insurance Facility (CCRIF), founded in 2007, make rapid payouts to member governments when a measured trigger, such as earthquake shaking or wind speed above a set level, is reached. Because the payout depends on the measurement rather than on a damage assessment, money arrives much sooner than an ordinary insurance payout.
Earthquake early warning systems detect the first, faster P waves of an earthquake near the epicentre and send automatic alerts before the slower, more damaging S waves and surface waves arrive further away.
System | Key facts | Limits |
|---|---|---|
Japan (Japan Meteorological Agency) | Public alerts since October 2007; uses data from 4,235 seismometers; alerts issued when two or more detect P waves; sent by TV, radio and cell broadcast to phones; trains slow and factories stop automatically | Places close to the epicentre feel shaking before any warning; false or exaggerated alerts, for example when aftershocks overlap |
United States (ShakeAlert, USGS and partners) | Public alerts in California from 2019, Oregon and Washington from 2021; delivered by apps, Wireless Emergency Alerts and Android phones; BART trains brake automatically | Some alerts were late or missed when an earthquake’s size was first underestimated |
Android Earthquake Alerts (Google) | Uses the motion sensors in millions of Android phones as a seismic network, so it can reach countries without expensive sensor networks | Accuracy depends on the number of phones; alerts can be wrong |
Warnings of a few seconds sound small, but they are enough to drop, cover and hold on, to stop trains and lifts, and to open fire station doors before power fails. Other technologies support resilience in the same way: satellite phones and messaging services keep people in contact when local networks fail, and apps share hazard maps and evacuation routes.
Communities also act together, at a scale between the household and the government. In community-based disaster risk reduction, residents map their own hazards, identify vulnerable neighbours, train volunteers and organise warnings and evacuations. It costs little, uses local knowledge and builds trust, but it needs support from governments and NGOs and cannot replace large investments such as engineering or monitoring networks.
Strategy | Scale and stakeholder | Strengths | Limitations |
|---|---|---|---|
Land-use zoning | Local and national government | Prevents exposure permanently; cheap once in place | Hard to apply where land is already built on; resisted by landowners; needs accurate maps |
Building codes | National government, engineers, builders | Saves the most lives in earthquakes | Useless without enforcement; covers new buildings only; raises building costs |
Drills and education | Schools, employers, communities | Low cost; fast, practised responses | Awareness fades between events; may not reach migrants or visitors |
Personal preparedness | Households | Very low cost; increases self-reliance | Depends on income, space and awareness |
Insurance | Households, insurers, governments | Speeds recovery; spreads costs | Unaffordable for the poor; does not save lives; may encourage building in risky places |
Early warning | National agencies, phone companies | Seconds of warning for millions at once | Little use near the epicentre; false alarms can reduce trust; expensive sensor networks |
Each strategy has gaps, so the most resilient places combine government planning, which reduces exposure and vulnerability for everyone, with personal resilience, which helps households cope with what remains. Equity is the main weakness of most strategies: insurance, retrofitting and even smartphones are least available to the people who are most vulnerable.
Pre-event management covers everything done before a hazard strikes to reduce its impact: monitoring and warning, engineering, planning, education and evacuation. The right mix depends on the hazard’s profile, especially its speed of onset and spatial predictability.
A slope fails when the shear stress pulling material downslope exceeds the shear strength holding it in place. Slope stabilisation either increases the strength or reduces the stress, and the most important single measure is drainage, because water raises pore-water pressure and reduces friction between grains.
Drainage: surface channels and deep drains carry water out of the slope, lowering pore-water pressure; at Portuguese Bend in California, pumping groundwater from wells slowed a large slide.
Regrading and terracing: cutting the slope to a lower angle or into steps reduces the downslope component of gravity.
Retaining walls hold back soil at the foot of the slope; rock bolts and soil nails tie loose surface layers to stable rock behind them; netting and sprayed concrete (shotcrete) stop small falls.
Vegetation and bioengineering: roots bind soil and plants remove water, a low-cost method suited to rural slopes.
Rockfall barriers and catch fences protect roads and railways below steep faces.
Retaining walls support a slope from below, while rock bolts and soil nails tie its surface layers to the stable material behind.
Monitoring warns of slope movement before failure. Inclinometers in boreholes measure movement at depth, GPS stations and satellite radar (InSAR) measure surface movement, and rainfall thresholds trigger landslide warnings when rain exceeds the amount that has caused failures before.
Hong Kong shows what a sustained programme can achieve. After landslides killed 71 people at Sau Mau Ping and 67 at Po Shan Road in 1972, and more at Sau Mau Ping in 1976, the government set up a geotechnical control office in 1977 to regulate slope design and maintenance. About 60,000 man-made slopes are now registered, older substandard slopes have been upgraded, and a landslip warning is issued when rainfall reaches set thresholds. The government estimates that the landslide risk from old man-made slopes has fallen to less than a quarter of its 1977 level.
Earthquakes kill mainly through collapsing buildings, so the most effective pre-event strategy is aseismic design: buildings that sway, bend or absorb shaking without falling down.
Base isolation separates a building from the ground on flexible bearings, often layers of rubber and steel, so that much less of the ground motion reaches the structure above. Dampers absorb energy like a car’s shock absorbers; a tuned mass damper, such as the large steel sphere near the top of Taipei 101 in Taiwan, swings against the building’s motion. Simple design rules matter as much: regular shapes, no weak open ground floors, and enough steel reinforcement tied correctly at joints.
YouTubeMost people live in existing buildings, so seismic retrofitting is essential. Schools, hospitals and older apartment blocks can be strengthened with steel bracing, concrete jackets around columns or new shear walls. Low-cost methods suit LICs: timber frames, confined masonry (brick walls framed by small reinforced concrete columns and beams) and improved traditional building techniques can save lives at a fraction of the cost of high-tech engineering.
A tsunami can cross an ocean in hours, so there is often time to warn distant coasts; near the source, the first waves can arrive within minutes. A tsunami warning system combines seismometers, which detect a large undersea earthquake, with sea-level gauges and deep-ocean pressure sensors, which confirm whether a tsunami has formed.
The Pacific Tsunami Warning Center in Hawaii has served the Pacific since 1949. The Indian Ocean had no system in 2004; the Indian Ocean Tsunami Warning System, coordinated by UNESCO, became active in June 2006, with seismic stations, national warning centres and deep-ocean DART buoys, and regional warning roles for Australia, India and Indonesia.
In the Mw 8.6 earthquake off Sumatra on 11 April 2012, the system worked as designed: India issued a high-level tsunami warning for the Andaman and Nicobar Islands, Sri Lanka ordered coastal evacuations, and people in Aceh moved to higher ground, many by car and motorcycle. The tsunami was small, but the event showed that the hardest part of a warning system is the "last mile", getting the warning to every person in time and giving them a safe route to follow.
Japan has built the world’s largest tsunami defences. After the 2011 Tōhoku tsunami overtopped many existing walls, a chain of seawalls roughly 400 km long was built along the north-east coast, with walls more than 12 m high in places, such as the 12.5 m wall along the waterfront of Rikuzentakata. Critics argue that the walls are very costly, block the view of the sea and access for fishing communities, and may create a false sense of security; some residents preferred to move homes to higher ground instead.
Evacuation is the most reliable way to save lives, because walls can be overtopped. Signs, evacuation routes and drills help people reach high ground; where it is too far away, vertical evacuation to the upper floors of strong buildings or purpose-built towers is used. Education about natural warnings, such as strong shaking or the sea drawing back, is vital for local tsunamis that arrive before any official warning.
Volcanoes usually give warning signs before they erupt, because rising magma pushes the ground up, cracks rock and releases gas. Volcano monitoring measures these signs continuously.
Method | What it measures | Sign of a coming eruption |
|---|---|---|
Seismometers | Earthquakes inside the volcano | Swarms of small earthquakes; harmonic tremor as magma moves |
GPS monitoring (GNSS) | Movement of fixed stations to a few millimetres | Uplift and outward movement as magma accumulates |
InSAR | Radar images from satellites compared over time | Maps of uplift over the whole volcano, without instruments on the ground |
Tiltmeters | Tiny changes in the angle of the ground | Flanks tilt outwards as the volcano inflates |
Gas sensors | Sulfur dioxide (SO₂) and carbon dioxide (CO₂) | Rising emissions as magma nears the surface |
Thermal cameras and drones | Surface temperature; crater changes | New hot spots, lava domes, crater lake changes |
Three of these methods measure ground deformation, the swelling of a volcano as magma collects beneath it.
GPS gives precise, continuous measurements at a few fixed points, while satellite radar maps deformation across the whole volcano at intervals of days.
Tiltmeters record the same swelling as a change in angle, continuously and at low cost.
Monitoring data feed an alert level system, which tells authorities and the public what to do. At Mount Pinatubo in the Philippines in 1991, the volcano observatory PHIVOLCS, assisted by the USGS, used a five-level scale based on earthquake swarms, tilt and sulfur dioxide. As alerts rose, the evacuation zone was widened from 10 km to 40 km, tens of thousands of people left, and the climactic eruption on 15 June (VEI 6) killed far fewer than it would have done otherwise; about 847 died, many when wet ash collapsed roofs during a typhoon.
Monitoring records are interpreted as time series. The graph is a typical GPS record from a volcano.
Where lava flows slowly, it can be diverted. Lava diversion uses earth barriers, channels or water to steer lava away from settlements. In 1973 on Heimaey, Iceland, about 7.3 million m³ of seawater was pumped onto advancing lava for five months, and the lava stopped short of blocking the island’s harbour.
On Etna in Sicily, engineers used explosives to breach the wall of a lava channel in 1983, the first attempt of its kind, and in 1992 they built an earth barrier and dropped concrete blocks into the main lava channel to protect the town of Zafferana Etnea. Diversion works only for slow, fluid lava: it cannot stop pyroclastic flows, which move at over 100 km h⁻¹, and it can send lava onto someone else’s land, which raises questions of fairness.
Lahars are managed with warning systems along valleys, such as tripwires and acoustic flow monitors, and with sabo dams, open dams that trap boulders and sediment while letting water through. Japan and Indonesia use them widely on volcanoes such as Sakurajima and Merapi.
Hazard | Strategy | Cost | Effectiveness | Suitability for LICs |
|---|---|---|---|---|
Mass movement | Drainage, terracing, vegetation | Low to moderate | High for shallow slides; less for deep slides | High: low-tech methods work |
Mass movement | Retaining walls, rock bolts, monitoring | High | High on known slopes | Low to moderate |
Earthquake | Aseismic design, base isolation | High | Very high if built and enforced | Low for high-tech methods; confined masonry is affordable |
Earthquake | Retrofitting schools and hospitals | Moderate | High | Moderate with aid funding |
Tsunami | Warning systems and evacuation | Moderate | High for distant tsunamis; limited near the source | High if the "last mile" works |
Tsunami | Seawalls | Very high | Moderate; can be overtopped | Low |
Volcano | Monitoring and alert levels | Moderate | High where acted on | Moderate; needs steady funding |
Volcano | Lava diversion | Moderate to high | Only for slow lava | Low |
The evaluation shows a common pattern. Strategies that reduce exposure and keep people informed, such as zoning, warnings, evacuation plans and simple drainage, are cheaper and more widely applicable than large engineering works. Engineering is most effective where the hazard is spatially predictable and the assets protected are valuable. The Goma Volcano Observatory, which could not pay for its internet connection in 2021, shows that even moderate-cost monitoring fails when funding is not sustained.
Grindavík is a fishing town on the Reykjanes Peninsula in south-west Iceland, about 50 km by road from Reykjavík, with about 3,700 residents before 2023. The peninsula is where the Mid-Atlantic Ridge, a divergent boundary, comes ashore, and after about 800 years of quiet it entered a new period of eruptions in 2021.
Nearby are the Svartsengi geothermal power station, which supplies hot water and heating to about 30,000 people on the peninsula, and the Blue Lagoon, one of Iceland’s most visited tourist sites. Iceland is a high-income country with a well-funded meteorological office and a national catastrophe insurance scheme, which makes Grindavík a test of how far pre-event management can protect a town built on top of an active rift.
From 24 October 2023 an intense earthquake swarm began near Svartsengi; more than 22,000 earthquakes were recorded by 10 November, the largest of magnitude 5.3. The Icelandic Meteorological Office used GPS stations and InSAR to show that the ground near Svartsengi was rising as magma collected about 4–5 km below. On 10 November a dyke of magma about 15 km long intruded beneath the town in roughly six hours, the GPS station in Grindavík dropped by about 1 m, and a graben opened through the streets. The civil protection authorities declared an emergency and evacuated the whole town that night: about 4,000 people, almost 1% of Iceland’s population.
The evacuation was made before any eruption, on the basis of monitoring alone. When the first eruption began on 18 December 2023, no one was in the town. Between then and mid-2025 there were nine eruptions, each preceded by a cycle of uplift at Svartsengi and a sudden fall when magma left the chamber. Hazard maps were updated after each event, and the zones around the town were reclassified as activity changed.
In November 2023 the Althing, Iceland’s parliament, approved a law to build earth barriers to protect Svartsengi, the Blue Lagoon and Grindavík. Building began around the power station that month and around the town on 2 January 2024. By 2025 about 14 km of barriers had been built from about 3 million m³ of rock and soil, at an estimated cost of ISK 10–11 billion, paid for partly by a temporary property tax on all Icelandic homes. In late 2024, water cannons fed with excess water from the power station cooled lava near the barriers.
The barriers worked for most of the eruptions. In May and June 2024 lava was deflected away from the power station and the town. They were not complete, however. On 14 January 2024 a fissure opened inside the barrier, about 100 m from the edge of the town, and lava destroyed three houses.
The February 2024 eruption cut the hot-water pipeline from Svartsengi, leaving about 20,000 people without hot water in winter for several days, and in November 2024 lava covered the Blue Lagoon’s car park. A worker filling a crack in Grindavík disappeared on 10 January 2024 and is presumed to have died, the first death linked to an eruption in Iceland since Heimaey in 1973.
Damaged property was covered by Iceland’s national Natural Catastrophe Insurance. In February 2024 the government passed a law allowing it to buy residents’ homes through a state company, Þórkatla, so that families could move on with the value of their property; more than 900 applications, covering about 930 properties, had been received by November 2024, at an expected cost of about ISK 75 billion. Former owners have the right to buy their homes back within three years.
The town reopened to the public on 21 October 2024, but by 2026 only about 40 to 60 homes were occupied, although about 1,100 people were still registered as residents. The schools reopened in August 2026 with about 40 pupils enrolled, compared with about 550 before the evacuation.
Strategy | Successes | Limitations |
|---|---|---|
GPS, InSAR and seismic monitoring | Detected magma accumulation weeks before each eruption; allowed evacuation before the first eruption | Could not predict the exact place or time of fissures, such as the one inside the barrier in January 2024 |
Evacuation and hazard zoning | No resident was killed by lava | Long-term displacement of about 4,000 people; town life largely ended |
Lava barriers and water cooling | Protected the power station, the Blue Lagoon and most of the town | Very expensive; three houses and the hot-water pipeline still lost |
Insurance and state buy-out | Allowed families to rebuild their lives elsewhere quickly | Very costly to the state; ended many residents’ link to the town |
Grindavík shows both the possibilities and the limits of pre-event management. In a wealthy country with strong institutions, monitoring and lava diversion prevented almost all deaths and protected critical infrastructure that serves 30,000 people. Yet the management could not save the town as a community: once the hazard became frequent, most residents chose to sell and leave. The choice of what to protect also involved power. The power station and the Blue Lagoon were protected first because of their national economic value, and the costs were spread across all Icelandic households through the property tax.
To what extent was the management at Grindavík successful, and for whom?
Suggest why lava diversion was possible at Grindavík but would not have helped at Fuego in 2018.
Examine whether the Grindavík approach could be used in a low-income country such as the DR Congo.
Sources: Icelandic Meteorological Office, 2023–2025; Icelandic Civil Protection, 2023; Natural Catastrophe Insurance of Iceland, 2024; Þórkatla, 2024; Wikipedia, 2023–2025 Sundhnúkur eruptions, 2026.
Post-event management begins the moment a hazard strikes and can last for decades. Its purpose is to save lives, meet urgent needs and then restore, and ideally improve, the affected community.
Rescue is the first phase, lasting hours to days. Survivors are found and freed, the injured are treated, and urgent needs for shelter, water and food are met.
Survival chances for people trapped in rubble fall steeply after the first three days, the "golden 72 hours", so speed matters more than anything else. Emergency relief, the provision of food, water, shelter and medical care, is the main activity during this phase.
After large earthquakes, national teams are joined by international urban search and rescue (USAR) teams, coordinated through the UN’s International Search and Rescue Advisory Group (INSARAG). After the 2023 Türkiye–Syria earthquakes, more than 141,000 people from 94 countries took part in the rescue effort, using listening devices, cameras on probes and trained dogs to locate survivors.
Rehabilitation lasts weeks to months. Temporary housing replaces tents, water, power and roads are repaired, schools and clinics reopen, and people begin to earn a living again.
Reconstruction lasts months to years: permanent homes, infrastructure and the economy are rebuilt.
The disaster response curve, proposed by Chris Park in 1991, shows how quality of life changes through the phases of a disaster. It is a sketch graph with time on the x-axis and quality of life, or level of normality, on the y-axis.
The shape of the curve differs between places. In an HIC the fall is usually smaller, because buildings and services withstand more of the hazard, and recovery is faster, because insurance, government funds and contractors are available. In an LIC the fall is deeper and recovery slower, and quality of life may never return to its previous level, especially if a second event strikes before recovery is complete.
Strengths | Limitations |
|---|---|
Simple and visual; shows the sequence of phases clearly | Quality of life is not measured; the curve is qualitative |
Allows events and places to be compared by depth and length of the dip | Phases overlap in reality: rescue in one district, reconstruction in another |
Shows that recovery can end above or below the starting level | One curve hides differences between groups within a community |
Links response to development and to pre-event preparation | Ignores slow-onset or repeated events, such as the Grindavík eruptions or a slow landslide |
The model is most useful for comparing rapid-onset events in contrasting places. It is least useful for events that unfold over years, and it should be supplemented by data on the different groups within a community, because the recovery of the wealthy can hide the slower recovery of the poor.
After a disaster, responders need to know where damage is worst, where people are trapped and which roads are open, and communications technologies now supply much of this.
Satellite imagery: the International Charter Space and Major Disasters, set up in 2000, lets national agencies request free satellite images of a disaster zone from space agencies worldwide, and the European Union’s Copernicus Emergency Management Service produces rapid damage maps, often within hours of an event.
Crowdsourced mapping: after the 2010 Haiti earthquake, volunteers around the world traced roads and buildings on satellite images in OpenStreetMap, and text messages from survivors were mapped on the Ushahidi platform. The Humanitarian OpenStreetMap Team now organises such mapping after most large disasters.
Drones map damage and inspect unsafe buildings and slopes where people cannot go.
Mobile phones and social media: "safety check" features let people report that they are safe; location data from phone networks show where displaced people have gone; mobile money allows aid agencies to send cash directly; digital identity records help survivors who have lost their documents to register for aid and prove ownership of land.
Search tools: acoustic sensors, cameras on probes and thermal imaging help USAR teams locate people trapped under rubble.
These technologies have clear limits. Power and phone networks often fail in the worst-hit areas; the digital divide means that older, poorer and rural people are least likely to have smartphones; misinformation spreads quickly on social media; and location data raise privacy concerns. Technology is most effective when it is used by local responders who know the area.
Reconstruction is an opportunity to reduce future risk. Build back better means rebuilding to stronger codes, moving homes out of the most dangerous zones and improving services, so that the community ends up less vulnerable than before. The phrase is written into the fourth priority of the Sendai Framework.
Successful recovery restores livelihoods and education quickly, because income and schooling are the foundations of human development, and it involves local people in decisions. Cash transfers, rebuilding grants paid in stages as safer homes are built, and the rapid reopening of schools all help. Christchurch’s red zone shows build back better at the scale of a city: rather than rebuild on land that liquefies, the government cleared more than 8,000 properties and turned the land along the Avon River into a planned river corridor park of about 600 ha.
Recovery can also fail. Reconstruction may be slow, as when people remain in temporary housing for years; aid may create dependency or reach the well connected first; corruption can divert funds and allow unsafe rebuilding; and relocation can move people far from their work. Recovery after the 2023 earthquakes in Türkiye raised exactly these questions, because the speed of rebuilding had to be balanced against the need to enforce the building rules that had failed.
Structured questions on this content often give a chart of disaster trends, a monitoring graph or a diagram of a strategy. Extended answers usually ask you to evaluate strategies or to discuss whether some approaches matter more than others, with named, located examples across hazard types and income levels.
The table shows the number of recorded geophysical disasters per decade (EM-DAT, CRED, via Our World in Data, 2025).
Decade | Earthquakes | Landslides | Volcanic activity |
|---|---|---|---|
1970s | 109 | 54 | 23 |
1980s | 173 | 119 | 31 |
1990s | 264 | 162 | 52 |
2000s | 284 | 199 | 59 |
2010s | 259 | 188 | 46 |
The frequency of earthquakes and eruptions is stable, but recorded geophysical disasters rose steeply from the 1960s to the 2000s because of better reporting and greater exposure.
Deaths are dominated by a few huge events, while economic losses keep rising; EM-DAT’s thresholds and gaps mean that trend data must be read with care.
Population growth and urbanisation into hazard zones will raise exposure; climate change adds to landslide risk; the Sendai Framework sets targets to 2030.
Adaptation combines government planning (zoning, building codes, drills) with personal resilience (preparedness, insurance, new technology such as earthquake early warning).
Pre-event strategies include slope stabilisation, aseismic design and retrofitting, tsunami warnings, defences and evacuation, and volcano monitoring, alert levels and lava diversion.
Grindavík shows that monitoring, evacuation and lava barriers can prevent deaths and protect infrastructure, but cannot always save a community.
Post-event management moves through rescue, rehabilitation and reconstruction; the Park model shows deeper, longer dips in LICs than in HICs.
Satellite mapping, crowdsourced maps and phones help responders, but are limited by outages, the digital divide and access; build back better aims to leave communities less vulnerable.
I can describe and explain global trends in geophysical events, disasters, deaths and losses.
I can evaluate the reliability of EM-DAT and other disaster data.
I can explain how population growth and urbanisation will change future exposure to geophysical hazards.
I can distinguish adaptation from mitigation and evaluate zoning, codes, preparedness, insurance and early warning.
I can explain pre-event strategies for mass movements, earthquakes, tsunamis and volcanoes with named examples.
I can analyse a GPS deformation time series and explain what it shows about a volcano.
I can draw and use the disaster response curve to evaluate post-event management in contrasting places.
I can examine how communications technologies support rescue, recovery and continuing human development.
Limits in lower-income countries: sparse gauges, poor maintenance, transboundary rivers where upstream data are not shared, and people who cannot evacuate or have nowhere to go; Pakistan 2022 shows that warnings alone could not prevent huge losses when about a third of the country was affected.
Warnings reduce deaths more than economic losses, since buildings, crops and infrastructure cannot be moved.
Good answers may be well structured (AO4) and may additionally offer a critical evaluation (AO3) which weighs the strengths and limitations of warning technology against other measures, and recognizes that the effectiveness of a warning depends on the last mile: communication, trust, education and the ability to act (vulnerability, power). Another approach might be to argue that the contrast between countries is not simply about wealth: some lower-income countries achieve large reductions in deaths through community-based systems, while some wealthy places fail to act on good forecasts.
For 5–6 marks, expect some weakly-evidenced outlining of flood warning technology and its benefits.
For 7–8 marks, expect a structured account which includes:
either well-evidenced explanation of the role of flood warning technology in countries at different levels of development
or a discursive conclusion (or ongoing evaluation) grounded in geographical concepts and/or perspectives.
For 9–10 marks, expect both of these traits.
NB. Maximum [6] if only one level of economic development is considered.
Marks | Level descriptor |
|---|---|
0 | The response does not reach a standard described by the descriptors below. |
1–2 | Too brief, lists unconnected information, not focused on the question and lacks structure. Knowledge is very general, with large gaps or errors; examples or case studies are missing or only listed. No analysis; terminology is missing or used incorrectly. |
3–4 | Too general, lacks detail, not focused on the question and largely unstructured. Outlines examples, statistics and facts, both relevant and irrelevant, with links to the question only listed. Basic terminology is used, with errors or inconsistently. No critical evaluation of evidence; any conclusion is irrelevant. |
5–6 | Partially addresses the question, with a narrow argument, an unsubstantiated conclusion and limited evaluation. Describes relevant supporting evidence (examples, case studies) and outlines links to the question. The argument repeats one point or covers only part of the question. Other perspectives, or strengths and weaknesses of evidence, are listed. |
7–8 | Addresses the whole question; the analysis is evaluated and the conclusion is relevant but lacks balance. Relevant evidence is described correctly and covers all the main points. The argument is clear but one-sided or unbalanced. Complex terminology is used correctly but not consistently. Other perspectives, or strengths and weaknesses of evidence, are described. |
9–10 | In-depth and specific to the question (topic and command term). Correct, relevant examples, statistics and detail are integrated and their link to the question explained. The argument is balanced, explaining complexity, exceptions and comparisons. Evaluation of evidence and perspectives is well developed, and the conclusion is balanced and aligned with the evidence. Logically structured and easy to follow. |
Examine the relevance of hazard magnitude and frequency for the management of geophysical hazard risk in one or more named places.
10 marks
Examine how education and hazard awareness affect the vulnerability of communities to geophysical hazards.
10 marks