Edexcel Specification focus:
‘Characteristics of tectonic hazards (magnitude, speed of onset, areal extent, duration, frequency, spatial predictability) can be compared using hazard profiles.’
This subsubtopic explores how tectonic hazards differ in nature and impact, using comparative characteristics to understand their complexity and predictability across global contexts.
Comparing Characteristics of Tectonic Hazards
Understanding Tectonic Hazards
Tectonic hazards are physical events arising from the movement of Earth's lithospheric plates. These include earthquakes, volcanic eruptions, and tsunamis. Each hazard type has unique characteristics, and analysing these helps geographers assess potential impacts and inform risk management strategies.
To compare different hazards systematically, geographers use hazard profiles.
Hazard Profile: A diagram or description that compares the physical characteristics of different tectonic hazards to understand their potential impacts and risks.
Hazard profiles allow geographers to visualise and contrast the nature of different tectonic events, particularly across geographical regions and development levels.
Key Characteristics Used in Hazard Profiles
Magnitude
Magnitude refers to the amount of energy released by a tectonic event.
Earthquakes are measured using the Moment Magnitude Scale (MMS), which quantifies seismic energy.
Volcanic eruptions are assessed using the Volcanic Explosivity Index (VEI), which considers eruption volume, height of the eruption column, and duration.
Tsunamis do not have a dedicated magnitude scale but are influenced by the magnitude and depth of the triggering earthquake or submarine landslide.
Higher magnitudes generally correlate with more severe impacts, but the vulnerability of the area also plays a crucial role.
Speed of Onset
This refers to how quickly the hazard manifests after the initiating event.
Earthquakes have an extremely sudden onset with no warning once stress is released along a fault.
Volcanic eruptions often have a slower onset, with precursory signals such as gas emissions, ground deformation, and seismic activity.
Tsunamis typically follow an earthquake or undersea displacement and can arrive within minutes to hours depending on distance from the epicentre.
The speed of onset affects the population's ability to respond in time, especially in vulnerable or densely populated areas.
Areal Extent
Areal extent describes the geographical area affected by the hazard.
Earthquake impacts can be local or regional, depending on fault length and depth.
Volcanic hazards tend to be more localised, though ash clouds can affect wider areas, even globally in rare cases (e.g. 2010 Eyjafjallajökull eruption).
Tsunamis may have the widest areal extent, especially when waves radiate across ocean basins and strike multiple coastlines.
The larger the areal extent, the more complex the emergency response and the broader the potential economic impact.
Duration
This is the length of time the hazard lasts.
Earthquakes generally last seconds to minutes, but their effects (aftershocks, structural damage) may persist.
Volcanic eruptions can last days to months, with prolonged environmental and societal disruption.
Tsunamis may involve a series of waves over several hours, but the inundation event typically occurs within minutes.
Longer durations often strain resources and complicate recovery, especially in areas with limited resilience.
Frequency
Frequency refers to how often a hazard of a particular type or magnitude occurs.
Low-magnitude earthquakes happen frequently, but high-magnitude earthquakes are less common.
Volcanic activity varies by volcano type and tectonic setting. Some volcanoes erupt repeatedly; others may lie dormant for centuries.
Tsunamis are relatively infrequent, particularly destructive ones, but when they occur, the impacts are often catastrophic.
High-frequency hazards may become normalised in local populations, whereas low-frequency events often catch communities unprepared.
Spatial Predictability
This characteristic assesses how accurately the location of the hazard can be predicted.
Earthquakes occur along known fault zones, especially at convergent and transform plate boundaries, but exact timing and location are unpredictable.
Volcanic eruptions are more spatially predictable, as they usually occur at specific volcanic cones or fissure systems.
Tsunamis depend on undersea disturbances, and although the source zone is known, the spread and impact location of waves are harder to forecast without real-time data.
Greater spatial predictability enhances preparedness and targeted mitigation strategies.
Constructing and Using Hazard Profiles
Hazard profiles typically compare multiple hazards along the six characteristics listed above.
These profiles help:
Identify the most dangerous hazards in a given area.
Support risk assessment and prioritisation of mitigation strategies.
Inform emergency planning and resource allocation.
Compare the hazard risk between different regions or countries.
For example:
A high-magnitude, sudden-onset, widespread tsunami is considered high-risk, especially for low-lying coastal regions.
A frequent, small-magnitude volcanic eruption with high predictability may pose limited threat if communities are well-prepared.
Hazard profiles also highlight differences in risk between countries at different levels of development. Developing countries may be more vulnerable due to limited infrastructure and response capacity, even if the physical characteristics of the hazard are less severe.
Limitations of Hazard Profiles
While useful, hazard profiles have limitations:
They often simplify complex events, excluding human factors such as governance, economic conditions, and cultural responses.
Some characteristics, like predictability, are qualitative, which may lead to subjective interpretations.
Secondary impacts such as fires, disease outbreaks, or long-term displacement are not always fully accounted for.
Despite these limitations, hazard profiles remain a valuable geographical tool to better understand, compare, and manage tectonic hazards. They encourage systematic thinking about risk and reinforce the need for contextual understanding in disaster planning.
FAQ
Speed of onset refers to how quickly a hazard occurs once the triggering event begins. For example, an earthquake starts almost instantaneously, while a volcanic eruption may develop over days or weeks.
Frequency, on the other hand, refers to how often a hazard occurs in a given area over time. Some locations may experience frequent low-magnitude earthquakes, while large tsunamis may only occur once every few decades.
These characteristics are independent — a hazard can occur quickly but rarely, or slowly but frequently.
Spatial predictability helps planners and emergency services focus mitigation efforts in areas most likely to experience a hazard.
For example:
Earthquakes are known to occur along plate boundaries, but pinpointing the exact fault or segment is difficult.
Volcanoes, in contrast, erupt from known locations, allowing for clear risk zones to be established.
Higher spatial predictability allows for zoning laws, evacuation plans, and targeted infrastructure investment to reduce risk.
Hazard profiles allow geographers to assess the physical nature of a hazard independently from human factors.
By comparing hazard characteristics in countries at different development levels, it becomes easier to identify:
Why similar physical events may have drastically different impacts
Where investment in infrastructure or early warning systems could reduce risk
This helps distinguish between the physical hazard itself and the population’s vulnerability to it.
Yes, different tectonic hazards can share similar characteristics depending on context.
For instance:
A low-magnitude earthquake and a small volcanic eruption might both have limited areal extent, short duration, and low impact.
A high-magnitude submarine earthquake and a major volcanic eruption could both be widespread, have long-term effects, and be hard to predict.
Hazard profiles focus on physical characteristics rather than hazard type, so overlapping profiles are possible.
Hazard profiles typically focus on measurable physical characteristics, which may not fully account for human vulnerability or cascading impacts.
Limitations include:
Not capturing secondary hazards like fires, landslides, or disease
Ignoring population density, preparedness, or governance quality
Treating qualitative traits like “predictability” as if they are uniform
As a result, the actual risk or impact can be greater than the profile suggests, especially in high-risk communities.
Practice Questions
Question 1 (2 marks)
Define the term "hazard profile" and explain one of its uses in understanding tectonic hazards.
Mark Scheme:
1 mark for a correct definition:
Hazard profile: A diagram or description that compares the physical characteristics of different tectonic hazards to understand their potential impacts and risks.
1 mark for explaining one valid use, e.g.:
They help compare the severity or impact of different hazard types.
They assist in planning and risk assessment by visualising hazard characteristics.
Question 2 (6 marks)
Explain how two characteristics from hazard profiles can influence the severity of tectonic hazard impacts. Use examples to support your answer.
Mark Scheme:
Up to 3 marks for each characteristic explained (maximum 2 characteristics):
1 mark for identifying a characteristic (e.g. magnitude, areal extent, speed of onset).
1 mark for explaining how this characteristic influences impact.
1 mark for an appropriate example to support the explanation.Indicative content may include:
Magnitude: Higher magnitude events (e.g. a 9.0 earthquake) release more energy and are likely to cause more damage and fatalities, especially in poorly prepared areas.
Areal extent: Events that affect wider areas can impact more communities, overwhelm response services and increase economic damage (e.g. the widespread effect of the 2004 Indian Ocean tsunami).
Speed of onset: Sudden hazards like earthquakes give little or no warning, limiting evacuation time and increasing potential loss of life.
Spatial predictability: More predictable events (e.g. volcanic eruptions) may allow for early warning systems and evacuations, reducing impact severity.
Levelled response guidance:
5–6 marks: Clear explanation of two characteristics with developed examples.
3–4 marks: Some explanation of one or two characteristics with basic examples.
1–2 marks: Descriptive or partial response with limited linkage to impact severity.
