AQA GCSE Geography (8035) · Paper 1

🌋 Natural Hazards

Revision notes written to the specification, with examiner tips and the required practicals. Every point here has flashcards in the Stickwise app.

Tectonic hazards

A natural hazard is a natural event that threatens people or property. The risk from hazards is rising as populations grow, cities spread into dangerous places, and climate change sharpens weather extremes.

The Earth is made up of layers: a core, surrounded by the mantle, surrounded by the crust. The crust is cracked into tectonic plates, which are dragged along a few centimetres a year by convection currents in the mantle below. Earthquakes and volcanoes cluster along the boundaries between plates, called plate margins.

Destructive marginTwo plates collide, and the denser oceanic plate is forced underneath the other and melts, in a process called subduction. This produces violent earthquakes and volcanoes, as seen around the Pacific Ring of Fire.

Constructive marginTwo plates move apart, and magma rises through the gap and cools into new crust. This produces gentler shield volcanoes, as in Iceland.

Conservative marginTwo plates slide past each other, sticking and then snapping suddenly. This produces earthquakes but no volcanoes, as along the San Andreas Fault.

People continue to live in hazard zones because they offer fertile volcanic soil, geothermal energy, tourism and mineral wealth, and because poverty or family ties can make leaving impossible. Hazard management is often summarised as the four Ps: monitoring using sensors, prediction, protection through building design, and planning for evacuation and drills.

🎯 Examiner tip: Case-study comparisons score well when they contrast rather than simply describe, for example Chile in 2010, with a magnitude of 8.8 and around 500 deaths thanks to strict building codes, against Nepal in 2015, with a magnitude of 7.8 but around 9,000 deaths due to unreinforced buildings and slow aid to remote areas. Wealth, rather than magnitude, is usually what determines the death toll, and different examples fit the same comparison.

Weather hazards & the UK

Global atmospheric circulation describes how air moves around the planet. Hot air rises at the equator, creating low pressure and daily rain, then travels towards the poles and sinks again at around 30° latitude, creating high pressure and the world's deserts. These circulation loops also drive the trade winds, and they explain why the world's climate zones sit where they do.

Tropical storms form over oceans warmer than 27°C, between 5° and 30° latitude, where warm moist air rises rapidly. The Earth's spin twists the rising air into a spiral around a calm centre called the eye. Climate change is expected to make tropical storms more intense and to widen the range of ocean they can form over; scientists are more confident about storms becoming stronger than about them becoming more frequent.

Typhoon Haiyan 2013A category 5 storm that struck the Philippines, killing around 6,300 people, leaving 4 million homeless, and destroying about 90% of the city of Tacloban. The response included mass evacuation and global aid, followed by a 'Build Back Better' rebuilding programme and new storm-surge warning systems.

Somerset Levels 2014A UK flood case study in which record January rainfall combined with rivers that had not been dredged caused more than 600 homes to flood for several weeks. The response was a £20 million Flood Action Plan covering dredging, raised roads and new pumping stations.

The UK experiences the whole range of weather hazards, including storms, floods, snow and drought, because several competing air masses meet over the country. These extremes are becoming more severe: UK temperature records keep being broken, including 40°C for the first time in 2022, and warmer air holds more moisture, so downpours are becoming heavier.

Climate change

Evidence for climate change comes from ice cores, in which trapped air bubbles record ancient CO₂ levels, as well as from tree rings and modern instrument readings. Together these show around 1°C of warming since 1900, alongside shrinking ice and rising sea levels. Natural causes, such as orbital cycles, volcanic activity and changes in solar output, cannot explain the recent rise on their own; human causes, including burning fossil fuels, deforestation and agriculture, can.

MitigationAction that tackles the cause of climate change, such as switching to renewable energy, capturing carbon, planting trees, and international agreements such as the Paris Agreement of 2015.

AdaptationAction that adjusts to the effects of climate change, such as growing drought-resistant crops, managing water supplies more carefully, and building sea walls and raised buildings.

🎯 Examiner tip: Questions on mitigation versus adaptation come up often, and it is easy to confuse the two. Mitigation reduces the causes of climate change, while adaptation deals with its effects. State clearly which is which, then give two examples of each.

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