Cambridge IGCSE Environmental Management 6: Natural hazards

Natural hazards become disasters when hazardous processes meet exposed and vulnerable people, buildings, infrastructure or ecosystems. Cambridge IGCSE Environmental Management 0680 Topic 6 requires more than naming an event. You need to connect its physical cause to its impacts, then judge how management before, during and after the event changes risk.

These notes follow sections 6.1 to 6.4 of the Cambridge syllabus for examinations in 2027, 2028 and 2029. Field investigation methods remain in the separate Environmental Management fieldwork hub.

6.1 Earthquakes and volcanoes

The Earth has a thin crust, a much thicker mantle and a central core. The crust is divided into tectonic plates. Slow convection currents within the mantle contribute to plate movement, so most earthquakes and volcanoes occur in belts near plate boundaries. A hotspot is different: magma rises within a plate and can form a chain of volcanoes as the plate moves over it.

The seven continents used in this syllabus are Africa, Antarctica, Asia, Europe, North America, Oceania and South America. Locating a hazard on a world map matters because the distribution provides evidence for plate movement.

Three boundary types explain contrasting hazards:

• At a divergent or constructive boundary, plates move apart. Magma rises into the gap, producing volcanic activity and shallow earthquakes.
• At a convergent or destructive boundary, one plate can be forced beneath another. Friction and sudden movement cause earthquakes, while melting and rising magma can form a line of volcanoes.
• At a conservative boundary, plates slide past one another. Stress builds when they stick and is released as an earthquake. Volcanoes are not normally produced because crust is neither created nor subducted.

An earthquake releases stored energy at the focus inside the Earth. The epicentre is the point on the surface directly above the focus. Magnitude describes the energy released and is reported using the Moment Magnitude Scale. Magnitude is not the same as impact: an event of lower magnitude can cause greater harm if buildings are weak, the population is dense or emergency response is limited.

A volcanic eruption can release lava, ash, water vapour, carbon dioxide, sulfur dioxide, volcanic bombs and fast-moving pyroclastic flows. Sulfur dioxide can contribute to acid rain. The severity of harm depends on the eruption, distance, wind, relief, preparedness and the number of people or habitats exposed.

Tectonic events may damage buildings, roads, power lines and water systems; destroy crops, livestock and habitats; start fires; trigger landslides or tsunamis; contaminate drinking water; increase water-related disease; and cause injury, death, displacement and financial loss. A complete causal chain is stronger than a list. For example, an earthquake can rupture a water pipe, sewage can enter the supply, and unsafe water can then increase disease.