D Geophysical hazards

Geophysical hazards studies earthquakes, volcanic eruptions and mass movements: the Earth processes that cause them, why they put some places and people at far greater risk than others, and how societies can prepare for and recover from them. The hazards themselves cannot be prevented, but the number of people they kill depends largely on human decisions about where and how people live.

Questions that frame the option

The option follows four lines of geographical inquiry. The first asks how geological processes give rise to hazard events of different types and sizes. The second asks how these physical systems create hazard risks that differ from place to place. The third asks why hazard events of similar size affect people so differently in different local contexts, and even within the same town. The fourth asks what can be done to lessen human vulnerability in future.

These inquiries lead to real questions that geographers try to answer with evidence:

• Why did the magnitude 7.0 earthquake in Haiti in January 2010 kill far more people than the much stronger magnitude 8.8 earthquake in Chile six weeks later?

• Why did earthquakes of the same magnitude, 7.8, kill more than 59,000 people in Türkiye and Syria in 2023 and two people in New Zealand in 2016?

• Why did the 2018 eruption of Volcán de Fuego kill at least 190 people, while the 2021 eruption of Nyiragongo, whose lava reached the edge of Goma, killed 32?

• Why did the Wayanad debris flow kill at least 420 people in 2024, while the Portuguese Bend landslide in California destroyed homes but killed no one?

• Can a town survive on top of an active rift, as Grindavík in Iceland has tried to since 2023?

What the option covers

The option has four subtopics. The first explains the physical systems, the second the distribution of hazards and why risk varies, the third six contrasting events in detail, and the fourth trends and management.

The six contrasting case studies are paired by hazard type. Each pair differs in the severity of its impacts, in its socio-economic setting or, for mass movements, in its physical character, so together they show both physical and human explanations at work. Other subtopics refer to these events from their own angles, such as the mechanism of an eruption or the management of a slope.

How the subtopics connect

The concept map shows the main links as a cycle. The geophysical process sets where events happen and how large they can be, which is the starting point of hazard risk. Economic, social, demographic and political risk factors then explain why the six events in the third subtopic had such different impacts. The lessons of those events shape preparation and response, and better monitoring of each process feeds back into the understanding of the physical systems.

At the centre of the map is the risk equation: risk rises with the hazard and with vulnerability, and falls as the capacity to cope rises. It explains why management concentrates on the human terms, which can be changed, rather than on the hazard, which cannot. The Pressure and Release model traces vulnerability from root causes, such as poverty and limited access to power, through dynamic pressures to the unsafe conditions of a particular place.

Key concepts in Geophysical hazards

The four key concepts run through the option, together with its specialised concepts: risk and vulnerability, which both vary with local context, and resilience and adaptation, which are the aims of management before and after an event.

The option links closely to the core. Risk, vulnerability and resilience are defined in the unit on climate, where they describe responses to global climate change; climate change also adds to geophysical risk through heavier rainfall that triggers landslides and through the collapse of glaciers and slopes as mountain ice and frozen ground thaw, as at Blatten in 2025.

The unit on population explains why exposure is rising: urbanisation spreads cities onto faults, steep hillsides and volcano flanks, and informal settlements on unstable slopes concentrate the people least able to cope. Tsunamis and storm surges connect the option to Oceans and coastal margins, and urban resilience links it to Urban environments.

How SL and HL differ

Geophysical hazards is one of seven options. SL students choose two options and HL students choose three. The content of the option is identical at both levels: every subtopic, case study and skill, including the six contrasting case studies, is studied in the same depth, and nothing on the option’s pages is HL only.

Both levels answer the same Paper 1 question on the option, marked with the same markbands. SL and HL differ only in the number of options studied and in the HL extension units, which HL students take in addition. Hazard risk and resilience return at HL in the extension unit on global risks and resilience.

Assessment

Geophysical hazards is examined in Paper 1. For each option studied there is a structured question built on a stimulus, worth 10 marks, followed by one extended answer worth 10 marks, chosen from two. The structured question typically has four parts: (a)(i) and (a)(ii), one mark each, read a value or fact from the stimulus; (b), two marks, asks for an outline of one cause or effect; and (c), three marks plus three, asks for two developed explanations.

Stimuli for this option are often maps of earthquakes, volcanoes and plate boundaries, a Benioff zone cross-section, a magnitude–frequency graph, an isoseismal map, a hazard event profile or data on deaths and losses. Typical short questions ask candidates to describe a distribution, estimate a depth or a recurrence interval, outline one secondary hazard or explain two reasons why vulnerability differs between groups. Extended questions usually offer one theme on processes or the relative importance of physical and human factors, and one on the effectiveness of pre-event or post-event management.