What you'll learn
This revision guide covers the tectonic hazards topic as examined by WJEC GCSE Geography. You'll understand why earthquakes and volcanic eruptions occur, how plate boundaries function, and the impacts of tectonic events in different economic contexts. The guide includes essential case study knowledge and exam-focused strategies to maximise your marks.
Key terms and definitions
Plate tectonics — the theory that Earth's crust is divided into large slabs (plates) that move due to convection currents in the mantle beneath them.
Destructive plate boundary — where two tectonic plates move towards each other, causing subduction of oceanic crust beneath continental crust or collision of continental plates.
Constructive plate boundary — where two tectonic plates move apart, allowing magma to rise and create new crust.
Conservative plate boundary — where two plates slide past each other horizontally without creating or destroying crust.
Epicentre — the point on the Earth's surface directly above the focus (origin point) of an earthquake.
Richter scale — a logarithmic scale measuring earthquake magnitude from 1 to 10, where each number represents a tenfold increase in ground movement.
Primary effects — the immediate impacts of a tectonic hazard, such as building collapse, ground shaking or lava flows.
Secondary effects — the subsequent impacts that occur as a result of primary effects, such as tsunamis, landslides, fires or disease outbreaks.
Core concepts
Structure of the Earth
The Earth consists of distinct layers that influence tectonic activity:
- Inner core: solid iron and nickel, approximately 1,200 km thick, temperatures reaching 5,500°C
- Outer core: liquid iron and nickel, approximately 2,200 km thick, generates Earth's magnetic field
- Mantle: semi-molten rock (magma), approximately 2,900 km thick, convection currents drive plate movement
- Crust: thin outer layer, 5-70 km thick, divided into oceanic (thinner, denser) and continental (thicker, less dense) types
The lithosphere comprises the crust and uppermost rigid mantle, broken into tectonic plates. Heat from radioactive decay in the core creates convection currents in the mantle, causing plates to move at 2-5 cm per year.
Types of plate boundaries and their features
Destructive (convergent) boundaries
Two scenarios occur at destructive boundaries:
Oceanic-continental convergence: The denser oceanic plate subducts beneath the continental plate, creating:
- Deep ocean trenches (e.g. Peru-Chile Trench)
- Fold mountains (e.g. Andes)
- Composite volcanoes with violent eruptions
- Frequent, powerful earthquakes at varying depths
- Example: Nazca Plate subducting beneath South American Plate
Continental-continental convergence: Neither plate subducts due to similar density, resulting in:
- Fold mountains (e.g. Himalayas)
- Powerful earthquakes but no volcanic activity
- Example: Indian Plate colliding with Eurasian Plate
Constructive (divergent) boundaries
Plates move apart, allowing magma to rise and create new crust:
- Mid-ocean ridges (e.g. Mid-Atlantic Ridge)
- Shield volcanoes with gentle, effusive eruptions
- Shallow earthquakes, generally low magnitude
- Rift valleys form on land (e.g. East African Rift)
- Example: Eurasian Plate and North American Plate diverging
Conservative (transform) boundaries
Plates slide horizontally past each other:
- No volcanic activity (no magma reaches surface)
- Earthquakes only, ranging from minor to very powerful
- Fault lines develop (e.g. San Andreas Fault, California)
- Friction causes plates to lock, building stress until sudden release
- Example: Pacific Plate sliding past North American Plate
Why people live in tectonically active areas
Despite risks, millions inhabit hazard zones due to:
Economic opportunities
- Volcanic soils contain minerals, supporting fertile agriculture (e.g. coffee in Indonesia, wine in Sicily)
- Geothermal energy generation (e.g. Iceland produces 25% of electricity from geothermal sources)
- Tourism revenue from volcanic landscapes and hot springs
- Mining of minerals concentrated by volcanic processes
Social and historical factors
- Established settlements with family and cultural ties
- Long periods between major events create false sense of security
- Improved building codes and monitoring reduce perceived risk
- Lack of economic means to relocate
Other benefits
- Building materials quarried from volcanic rock
- Flat land on floodplains near tectonically active regions
Monitoring, prediction and protection
Monitoring earthquakes
- Seismometers detect ground movements and tremors
- Laser reflectors measure plate movement along fault lines
- Radon gas detectors identify gas released before earthquakes
- Animal behaviour observation (controversial, not scientifically reliable)
Earthquakes cannot be accurately predicted, but monitoring identifies high-risk areas and times.
Monitoring volcanoes
- Tiltmeters measure ground swelling as magma rises
- Thermal imaging detects temperature increases
- Gas spectrometers analyse sulphur dioxide emissions
- Seismometers record harmonic tremors indicating magma movement
Volcanic eruptions can be predicted hours to weeks in advance, allowing evacuations.
Protection strategies
Immediate responses:
- Search and rescue teams with specialist equipment
- Emergency shelters and field hospitals
- International aid and disaster relief funds
- Evacuation procedures
Long-term planning:
- Earthquake-resistant building design (flexible steel frames, shock absorbers, deep foundations)
- Land-use zoning restricting development in high-risk areas
- Public education and evacuation drills
- Hazard mapping to identify vulnerable zones
- Reinforcing existing infrastructure
Impacts in contrasting economic contexts
Tectonic hazards affect high-income countries (HICs) and low-income countries (LICs) differently:
High-Income Countries (HICs)
Advantages:
- Strict building codes with earthquake-resistant design
- Advanced monitoring and warning systems
- Well-funded emergency services
- Comprehensive insurance coverage
- Effective evacuation infrastructure
Challenges:
- High economic costs (insured losses, business disruption)
- Dense urban populations increase casualty risk
- Complex infrastructure vulnerable to damage
Low-Income Countries (LICs)
Challenges:
- Poor building quality, often unreinforced masonry
- Limited monitoring technology
- Inadequate emergency services and medical facilities
- Dense informal settlements in high-risk areas
- Dependence on international aid
- Weaker governance and corruption affecting relief distribution
Advantages:
- Lower economic costs in absolute terms
- Traditional building methods sometimes earthquake-resistant
The death toll is typically far higher in LICs, whilst economic losses (in monetary value) are higher in HICs.
Case study requirements
WJEC requires knowledge of:
- An earthquake in a low-income country: causes, primary and secondary effects, immediate and long-term responses
- An earthquake in a high-income country: causes, primary and secondary effects, immediate and long-term responses
- A volcanic eruption: causes, primary and secondary effects, immediate and long-term responses
Example LIC earthquake: Haiti, 12 January 2010
Causes:
- Conservative boundary between Caribbean and North American plates
- Magnitude 7.0, focus 13 km deep
- Epicentre 25 km from Port-au-Prince
Primary effects:
- 230,000 deaths, 300,000 injured
- 1.5 million homeless
- 250,000 buildings collapsed, including presidential palace
- Port and airport damaged
Secondary effects:
- Cholera outbreak (7,000 deaths)
- Looting and crime increased
- 2 million without food/water
- Economic losses of $8 billion (120% of GDP)
Immediate responses:
- International rescue teams arrived within 24 hours
- $100 million aid pledged immediately
- Field hospitals established
- Water purification units deployed
Long-term responses:
- $10 billion pledged for reconstruction (not all delivered)
- 'Building Back Better' programme with improved codes
- Cash-for-work schemes
- Slow progress: 6 months later, 98% of rubble uncleared
Example HIC earthquake: L'Aquila, Italy, 6 April 2009
Causes:
- Destructive boundary between African and Eurasian plates
- Magnitude 6.3, focus 10 km deep
- Epicentre near L'Aquila, central Italy
Primary effects:
- 308 deaths, 1,500 injured
- 67,500 homeless
- Thousands of buildings damaged, including historic structures
- University halls of residence collapsed
Secondary effects:
- Economic losses of $16 billion
- Tourism industry severely affected
- Aftershocks caused psychological trauma
- Cultural heritage sites damaged
Immediate responses:
- Search and rescue within hours
- 40,000 evacuated to coastal hotels
- Emergency tents and temporary housing
- Italian Red Cross provided medical care
Long-term responses:
- €1.5 billion reconstruction fund
- Strengthening of historic buildings
- Modern earthquake-resistant buildings constructed
- Controversial prosecution of scientists for inadequate warning
Example volcanic eruption: Eyjafjallajökull, Iceland, April 2010
Causes:
- Constructive boundary where North American and Eurasian plates diverge
- Mid-Atlantic Ridge runs through Iceland
- Ice cap volcano producing explosive ash eruption
Primary effects:
- No deaths
- 800 people evacuated from local area
- Ash plume reached 11 km altitude
- Ice melt caused flooding (jökulhlaup)
Secondary effects:
- 100,000 flights cancelled across Europe (8 million passengers stranded)
- Economic losses of $5 billion globally
- Farmers lost livestock to ash inhalation
- Ash contaminated water supplies
Immediate responses:
- Exclusion zone established around volcano
- European airspace closed as precaution
- Emergency shelters for evacuees
- Scientists monitored eruption intensity
Long-term responses:
- Improved ash monitoring systems
- Review of aviation safety procedures
- Compensation claims to airlines
- Increased tourism to Iceland ('disaster tourism')
Worked examples
Question 1: Explain why earthquakes occur at conservative plate boundaries. [4 marks]
Mark scheme answer: At conservative plate boundaries, two tectonic plates slide horizontally past each other (1 mark). The plates do not move smoothly but become locked due to friction between them (1 mark). Stress and pressure build up over time as the plates attempt to move (1 mark). When the pressure exceeds the friction, the plates suddenly jerk past each other, releasing energy as seismic waves that cause earthquakes (1 mark).
Question 2: Compare the impacts of earthquakes in countries at different levels of economic development. [6 marks]
Mark scheme answer: In low-income countries (LICs), death tolls are typically much higher because buildings are poorly constructed without earthquake-resistant design (1 mark). For example, in Haiti (2010), 230,000 people died partly due to weak concrete buildings (1 mark). In contrast, high-income countries (HICs) like Italy have strict building codes, resulting in fewer casualties—L'Aquila (2009) had 308 deaths despite a significant earthquake (1 mark).
However, economic costs in monetary terms are often higher in HICs due to expensive infrastructure (1 mark). HICs also have better emergency responses with well-funded rescue services arriving quickly, whilst LICs depend heavily on international aid which takes longer to arrive (1 mark). Long-term recovery is faster in HICs because governments have resources to rebuild, whereas LICs like Haiti still had 98% of rubble uncleared six months after the earthquake (1 mark).
Question 3: Assess the effectiveness of methods used to predict volcanic eruptions. [9 marks + 3 SPaG]
Mark scheme answer structure: Introduction: Brief statement that volcanic eruptions can be predicted with reasonable accuracy using multiple monitoring techniques (1 mark).
Methods and effectiveness:
- Tiltmeters measure ground deformation as magma rises beneath volcanoes, providing several days' warning (2 marks, including example/detail)
- Thermal imaging detects increasing temperatures, allowing authorities to identify imminent eruptions (2 marks)
- Gas spectrometers analyse sulphur dioxide emissions which increase before eruptions, giving time for evacuation (2 marks)
- Seismometers detect harmonic tremors caused by magma movement through the crust (1 mark)
Evaluation:
- These methods successfully predicted eruptions like Eyjafjallajökull (2010), allowing 800 people to be evacuated with no deaths (1 mark)
- However, prediction is not perfect—timing can be uncertain by days or weeks, creating 'false alarms' that reduce public trust (1 mark)
- Methods are expensive, so less available in LICs where vulnerability is highest (1 mark)
Conclusion: Overall assessment of effectiveness with justified judgement (1 mark)
SPaG: 3 marks for accurate spelling, punctuation and grammar throughout.
Common mistakes and how to avoid them
Confusing plate boundary types: Remember—destructive boundaries involve collision/subduction, constructive boundaries involve plates moving apart, conservative boundaries involve plates sliding past. Draw annotated diagrams in revision to cement understanding.
Mixing up primary and secondary effects: Primary effects happen immediately (building collapse, deaths), secondary effects follow (disease, economic decline). Use the mnemonic "Primary comes before Secondary" and always check timing in your answers.
Vague case study detail: Examiners want specific facts—names, dates, numbers. "Many people died" scores no marks; "230,000 people died in Haiti" does. Create fact cards for each case study with precise data.
Ignoring command words: "Explain" requires reasons/causes, "Describe" requires characteristics, "Assess" or "Evaluate" requires judgement with evidence. Underline command words in exam questions before writing.
Stating management methods without explaining how they work: Don't just list "earthquake-resistant buildings"—explain that flexible steel frames absorb seismic waves, or shock absorbers in foundations reduce shaking.
Assuming all LICs or HICs respond identically: Economic development is a spectrum. Use specific country examples rather than generalising about all LICs or HICs.
Exam technique for "Tectonic Hazards"
Learn three detailed case studies: WJEC questions require specific named examples. Memorise at least 8-10 facts for each case study (location, causes, magnitude, death toll, specific effects, specific responses). Generic knowledge scores minimal marks.
Structure extended answers using PEE: Point, Evidence, Explanation. Make a clear statement, support it with case study evidence or data, then explain the geographical process or significance. For 6-9 mark questions, aim for 3-4 developed PEE paragraphs.
Use geographical terminology accurately: Terms like "subduction," "epicentre," "seismometer" demonstrate subject knowledge. Define terms when first used in longer answers to show full understanding.
Practice diagram annotation: WJEC often asks students to complete or label diagrams of plate boundaries or Earth structure. Practice drawing and labelling these without notes until automatic.
Quick revision summary
Tectonic hazards occur at plate boundaries where Earth's lithospheric plates interact. Destructive boundaries create earthquakes and violent volcanoes through subduction; constructive boundaries produce gentle volcanic activity; conservative boundaries generate earthquakes only. Effects vary dramatically between HICs and LICs due to differences in building quality, emergency preparedness and economic resources. Volcanic eruptions can be predicted using tiltmeters, gas monitoring and thermal imaging, whilst earthquakes remain unpredictable. Detailed case study knowledge with specific facts is essential for WJEC exam success.