Why do tropical cyclones only form over warm tropical oceans?
They need sea surface temperatures above ~27 degrees C to a depth of 50m to provide energy through evaporation, plus enough Coriolis effect (away from the equator) to spin. Learn it step by step →
Hazards & Tectonics is a core part of A-Level Geography. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
Tropical cycloneLow-pressure storm with sustained winds >118 km/h; called hurricane, typhoon or cyclone regionally.
Eye wallRing of intense thunderstorms around calm eye; strongest winds and rain.
Storm surgeSea level rise from low pressure and wind; Hurricane Katrina surge reached 8.5 m.
Subduction zoneConvergent plate boundary where oceanic crust dives beneath; sites of largest earthquakes.
Mercalli scaleEarthquake intensity from felt effects (I-XII); contrast with magnitude scales.
LiquefactionSaturated soil loses strength during shaking; collapsed buildings in Christchurch 2011.
Questions where students often pick the tempting wrong answer — make sure you know the right one:
Why do tropical cyclones only form over warm tropical oceans?✗ Hurricanes form wherever there are strong winds over the sea.✓ They need sea surface temperatures above ~27 degrees C to a depth of 50m to provide energy through evaporation, plus enough Coriolis effect (away from the equator) to spin.
Why do earthquakes typically cause more deaths in LICs than HICs?✗ LICs have more earthquake deaths because more earthquakes happen there.✓ LICs often have poorly enforced building codes, weak emergency response, dense informal housing and limited preparedness — not because the earthquakes are stronger.
Practise Hazards & Tectonics — free games
Test yourself with these quick revision games for this topic:
