What is a natural hazard?

A natural hazard is a natural event that has the potential to threaten life or damage property. They fall into three groups: tectonic (earthquakes, volcanoes), atmospheric (tropical storms, extreme weather) and geomorphological (landslides, flooding).

Plate tectonics theory

The Earth's crust is split into tectonic plates that float on the semi-molten mantle and move due to convection currents. There are two types of crust: oceanic (denser, thinner, younger) and continental (less dense, thicker, older).

Plate boundaries

• Destructive (convergent): plates move together, denser oceanic crust subducts under continental crust, causing composite volcanoes and powerful earthquakes, eg the Nazca and South American plates.
• Constructive (divergent): plates move apart, magma rises to fill the gap, forming shield volcanoes and shallow earthquakes, eg the Mid-Atlantic Ridge.
• Conservative: plates slide past each other, no volcanoes, but pressure builds and releases as strong earthquakes, eg the San Andreas Fault.
• Collision: two continental plates meet, crust crumples upwards to form fold mountains, eg the Himalayas.

Volcanoes

Composite volcanoes have steep sides, erupt violent thick lava (viscous, high in silica) and form at destructive boundaries. Shield volcanoes have gentle slopes, erupt runny lava (low viscosity) frequently but less violently, and form at constructive boundaries or hotspots.

Earthquakes

Measured on the Richter scale (magnitude) or the Mercalli scale (observed effects). The focus is the point underground where the earthquake starts; the epicentre is the point on the surface directly above the focus. Seismic waves radiate outward from the focus.

Managing tectonic hazards

• Monitoring: seismometers, satellite imagery, gas/tilt sensors on volcanoes.
• Prediction: patterns of past activity help forecast, though earthquakes cannot be predicted precisely.
• Protection: earthquake-resistant buildings (cross-bracing, base isolators, automatic shutoff valves).
• Planning: evacuation routes, hazard maps, drills and exclusion zones.

Common mistakes

• Mixing up focus and epicentre.
• Saying earthquakes only happen at destructive boundaries (they happen at all boundary types).
• Forgetting conservative boundaries have no volcanoes.
• Confusing shield (runny lava, gentle) with composite (thick lava, steep) volcano characteristics.
• Not linking case study impacts to development level (LICs suffer more due to poor building standards and slower emergency response, HICs cope better due to funding and planning).

The UK weather hazard

The UK gets extreme weather from the position of the jet stream and the collision of tropical maritime, polar maritime and polar continental air masses. Extreme UK weather events include storms (eg named storms bring gusts over 90mph), flooding (like Cumbria 2015, over 300mm rain in 24 hours) and heatwaves (UK record temperature 40.3C, Coningsby, July 2022). Extreme weather is becoming more frequent due to climate change.

Global atmospheric circulation

The three-cell model explains global climate belts. Warm air rises at the Equator (low pressure, heavy rainfall) and sinks at 30 degrees North and South (high pressure, hot deserts like the Sahara). Air rises again at 60 degrees (temperate, unsettled weather) and sinks at the poles (high pressure, cold and dry). This circulation creates the pattern of tropical rainforest, hot desert and temperate climate belts. Common mistake: students forget air always rises where it is warm and sinks where it is cool, driving wind belts between the cells.

Tropical storms

Tropical storms (hurricanes, cyclones, typhoons - same feature, different names by region) form over oceans at least 26.5C, between 5 and 30 degrees latitude, where the Coriolis effect is strong enough to create spin. They lose energy over land or cold water because the moisture supply is cut off. The Saffir-Simpson scale rates them Category 1 to 5. The calm centre is the eye, surrounded by the eyewall where winds are strongest.

Ecosystems

A tropical rainforest has a four-layer structure: emergent, canopy, under canopy and shrub layer. Nutrient cycling is rapid because heat and rainfall speed up decomposition, but soils are nutrient-poor as nutrients are stored in the biomass, not the ground. Deforestation causes soil erosion, loss of biodiversity and disrupts the water cycle. Hot deserts (eg Sahara) have adapted plants (xerophytes, like cacti with waxy skin and long roots) and animals (nocturnal behaviour, large ears to lose heat) to cope with under 250mm rainfall a year and extreme temperature ranges.

Common mistakes

• Confusing weather (short-term, day to day) with climate (long-term average pattern).
• Saying hurricanes form 'because of warm water' without adding the 26.5C threshold and 5-30 degree latitude band.
• Forgetting nutrient cycling arrows must show fast transfer in rainforests, not slow.

River processes

Rivers erode, transport and deposit material as they flow from source to mouth. Erosion has four types: hydraulic action (force of water), abrasion (load scrapes the bed and banks), attrition (load particles collide and get smaller/rounder) and solution (dissolving soluble rock like limestone). Transport happens by traction (large rocks rolled), saltation (bouncing pebbles), suspension (fine sediment carried in the water) and solution (dissolved material).

Long profile landforms

In the upper course, rivers form V-shaped valleys, interlocking spurs and waterfalls with plunge pools, caused by differential erosion between hard and soft rock. In the middle course you get meanders, formed by helicoidal flow: faster water on the outer bend erodes to form a river cliff, slower water on the inner bend deposits to form a slip-off slope. In the lower course, meanders can be cut off to form ox-bow lakes, and floodplains and levees form from repeated flooding and deposition.

Coastal processes and landforms

Coasts are shaped by the same four erosion types plus longshore drift, which moves sediment along the coast in a zig-zag pattern following the prevailing wind direction (swash goes up the beach at the wind angle, backwash returns straight down the steepest gradient under gravity). Erosional landforms include headlands and bays (formed on discordant coastlines where hard and soft rock alternate), caves, arches, stacks and stumps (formed in sequence at headlands). Depositional landforms include beaches, spits (with a curved end shaped by a change in wind direction or river current) and bars (formed when a spit joins two headlands, trapping a lagoon).

Management strategies

Hard engineering for rivers includes dams and reservoirs, channel straightening and embankments. Soft engineering includes floodplain zoning and afforestation. For coasts, hard engineering includes sea walls, groynes and rock armour; soft engineering includes beach nourishment and managed retreat (deliberately allowing the sea to flood an area).

Common mistakes

• Do not muddle backwash (straight down the beach, gravity) with swash (up the beach, at the wind angle) — this is the cause of longshore drift.
• Remember helicoidal flow explains WHY meanders erode on the outside and deposit on the inside — always link cause to landform.
• Groynes trap sediment on the updrift side, which can starve beaches further along the coast of material — a classic exam consequence question.
• Hydraulic action and abrasion are often confused: hydraulic action is the force of water alone, abrasion needs the river's load to scrape material.

Urban issues and challenges (Edexcel GCSE Geography B, Topic 6)

Urbanisation is fastest in NEEs (Newly Emerging Economies) like Nigeria and India, driven by rural-urban migration (push: poor services, drought, lack of jobs) and pull factors (jobs, education, healthcare). Megacities (10 million+ people) are growing mostly in Africa and Asia.

Case study 1: Lagos, Nigeria (NEE city)

• Lagos is Nigeria's largest city, population around 21 million, growing due to rural-urban migration and natural increase.
• Opportunities: informal jobs (over half the workforce), Makoko floating school, small businesses.
• Challenges: squatter settlements like Makoko (stilt housing over water), poor sanitation, traffic congestion.
• Improvement schemes: site and service schemes, self-help schemes where residents improve their own homes with council support (e.g. providing materials, water, electricity connections).

Case study 2: A UK city (commonly Bristol or London)

• Migration (national and international) has shaped the ethnic and cultural make-up of UK cities.
• Urban deprivation: inequality between inner-city and suburban areas shown by indices like the IMD (Index of Multiple Deprivation).
• Urban sprawl leads to loss of greenfield land; solutions include Green Belt policy and brownfield redevelopment.
• Traffic and pollution: solutions include park and ride schemes, cycle lanes, and Clean Air Zones/Low Emission Zones.
• Urban regeneration example: London Docklands or a local dockland regeneration scheme, turning derelict industrial land into housing and business space.

Sustainable urban living

• Sustainable cities balance environmental, social and economic needs for the future without compromising resources.
• Features: renewable energy, efficient public transport, green spaces, recycling schemes, water and energy conservation, mixed land use.
• Curitiba (Brazil) is a classic example of sustainable transport (Bus Rapid Transit system).

Common mistakes

• Do not confuse a squatter settlement (informal, self-built) with council housing.
• Learn specific named case studies and use accurate figures, not vague statements.
• Always link urbanisation causes to push AND pull factors, not just one side.
• Remember NEE cities face different challenges from UK cities: focus infrastructure and services for NEEs, focus inequality and regeneration for the UK.
• Use the term 'informal settlement' or 'squatter settlement', never 'slum' in exam answers, as examiners prefer neutral geographical terminology.

What this topic covers

The changing economic world looks at global development gaps, why they exist, and how countries try to close them. You need one detailed case study of an NEE (Newly Emerging Economy - usually Nigeria or India) and one UK example of how the economy is changing.

Measuring development

• GNI per capita: total income divided by population, in US dollars.
• HDI (Human Development Index): combines life expectancy, education (literacy and years of schooling) and income into a score from 0 to 1.
• Birth rate, death rate and infant mortality rate are social measures.
• Single measures (like GNI) can mislead because they hide inequality - HDI is more reliable as it's composite.

The Demographic Transition Model (DTM)

• Five stages, moving from high birth and death rates (Stage 1) to low birth and death rates (Stage 5).
• Population grows fastest in Stage 2 (death rate falls, birth rate stays high) - typical of many LICs.
• NEEs sit mainly in Stage 3, where birth rate starts falling due to development.

Causes of uneven development

• Physical: climate (drought/disease like malaria), landlocked location, few natural resources.
• Historical: colonialism drained resources and wealth from many LICs.
• Economic: trade imbalances, debt, and reliance on primary products with volatile prices.

Consequences of uneven development

• Wealth: measured by GNI/HDI gaps between countries.
• Health: disease prevalence, e.g. malaria linked to poverty in tropical LICs.
• Migration: people move from poorer to richer regions, causing brain drain and remittances.

Strategies to reduce the gap

• Investment: foreign direct investment (FDI) brings jobs and infrastructure.
• Aid: top-down (government-to-government) or bottom-up (small NGO projects, e.g. water wells).
• Intermediate technology: appropriate, low-cost tech that locals can maintain themselves.
• Fair trade: guarantees producers a minimum price, reducing exploitation.
• Debt relief: cancelling debt frees money for health and education.
• Microfinance loans: small loans help set up businesses in LICs/NEEs.

Common mistakes

• Mixing up LIC, NEE and HIC - always check the classification the question uses.
• Forgetting named case study detail (Nigeria/India TNC examples, UK example like South Wales or Cambridge).
• Confusing GNI (income measure) with HDI (composite measure) - know exactly what each includes.
• Writing about 'poor countries getting rich' too vaguely - always link causes to consequences with specific evidence.

What is resource management?

Resources are things people need: food, water and energy. Demand for all three is rising globally because of population growth, rising incomes and changing diets and lifestyles. A resource is 'insecure' when supply cannot reliably meet demand.

Food

• Global food production has risen but distribution is unequal - some regions have surplus, others deficit.
• Factors affecting supply: climate (drought/flooding), technology, pests and disease, water stress, conflict, and cost of inputs.
• Impacts of food insecurity: undernutrition, rising food prices, land grabs, and increased conflict over farmland and water.
• Sustainable solutions include appropriate technology, permaculture, and biological pest control rather than heavy chemical use.

Water

• Water stress occurs when demand approaches or exceeds available supply.
• Physical water scarcity: not enough water exists (e.g. arid climates). Economic water scarcity: water exists but lack of infrastructure/investment prevents access, common in parts of sub-Saharan Africa.
• Causes of rising demand: population growth, industrialisation, irrigation for agriculture, and domestic consumption rising with living standards.
• Sustainable schemes: small-scale, community-run and appropriate to local conditions - e.g. rainwater harvesting, drip irrigation - tend to work better long term than large dams.

Energy

• Global energy mix still dominated by fossil fuels (oil, gas, coal) but renewables are growing fastest.
• Factors affecting supply: physical availability of resources, cost of extraction, technology, and political decisions/energy security concerns.
• Impacts of energy insecurity: exploration of extreme environments (deep sea, Arctic), use of fossil fuels beyond their peak, and international conflict over supply routes.

Fieldwork skills - the exam essentials

Edexcel expects you to know the enquiry process in order:

1. Title, aim and hypothesis

2. Risk assessment and location choice, justified

3. Methods of data collection (primary and secondary; qualitative and quantitative)

4. Sampling method (random, systematic, stratified) - and why it suits the study

5. Presentation techniques (graphs, GIS, annotated photos, maps)

6. Analysis and drawing conclusions linked back to the hypothesis

7. Evaluation - limitations, reliability, accuracy, and how you could improve it

Common mistakes

• Confusing physical and economic water scarcity - always say which one and why.
• Vague fieldwork answers with no named location or specific method - examiners want detail, e.g. 'systematic sampling every 10 metres along a transect', not just 'sampling'.
• Forgetting to evaluate: every fieldwork question can ask 'how could you improve reliability?' - always have an answer ready (bigger sample size, repeat readings, different time of day).
• Mixing up food/water/energy case study facts - keep separate named examples for each.