A-Level Geography: Hazards and Tectonics

Hazards is examined on two things: whether you can name a mechanism, and whether you understand that a disaster is not simply a larger event. Every question here is built on one or the other.

The margins are given as observations rather than labels. Shallow earthquakes along a line, two plates sliding past one another, and no volcanoes anywhere: the absence is the evidence, because without subduction there is nothing to melt and nothing to rise. Then a trench, deep as well as shallow earthquakes, and explosive volcanoes inland — where the answer has to name the subduction and the melting rather than say the word "destructive". Eruptive style is decided by silica and therefore by viscosity, which is what allows gas to leave quietly or traps it until it does not.

Magnitude and intensity are separated on the ground rather than in a definition: one event, one magnitude, and two neighbourhoods reporting entirely different experiences because one sits on granite and the other on saturated sediment. The logarithmic scale gets its own question, with the answer that a whole step multiplies the recorded amplitude by about ten while the energy rises by a much larger factor — the common error being to treat one step as a doubling, and the second common error being to assume both quantities scale the same way.

Then the human half. Two regions meet the same magnitude; one has enforced building codes, a warning system and settlement off the steep ground, and the other has none, and the difference in outcome is vulnerability rather than a bigger earthquake. An agency does three things — names a date, publishes a thirty-year probability, funds codes and drills — and the answer has to label all three and say plainly that the first is not something seismology can currently do. Park's response curve is identified from what is being done in the district, not from how many months have passed: services back, temporary housing occupied, rebuilding not started, which is rehabilitation between relief and reconstruction. A community stays beside a volcano for fertile soil, family and work, which is a trade-off rather than ignorance, and "they do not know the risk" is offered to anyone who reaches for it. And an event whose shaking cracked a few walls but triggered a slope failure that did the real damage closes the set, because a hazard assessment that stops at the primary event stops too early.

Every place, event and figure described is invented. No real earthquake, volcano, town or country is named, and no measurement is attributed to a real event. Nothing is reproduced from any exam board specification, past paper or mark scheme.

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• Identify a plate margin from the evidence observed there, including what is absent
• Explain a subduction margin by its mechanism rather than by its label
• Trace eruptive style back to silica content and viscosity
• Separate magnitude from intensity, and explain a difference between two sites
• State what one step on a logarithmic magnitude scale changes, and what it does not
• Explain a disaster as a hazard meeting vulnerability
• Distinguish prediction, forecasting and preparedness, and say which is not currently available
• Place a situation on Park's response curve from what is being done
• Read continued settlement in a risky place as a trade-off, and follow a secondary hazard chain

Ten invented regions and events: a fault with shallow earthquakes and no volcanoes, a trench with explosive volcanoes inland, two volcanoes distinguished by viscosity and gas, one earthquake felt differently on granite and on sediment, a whole step on a logarithmic scale, two regions meeting the same magnitude with and without building codes, an agency naming a date and publishing a probability, a district eight months after an event, a community beside a volcano, and shaking that cracked walls and moved a hillside. Twelve flashcards carry the vocabulary — the three margins, subduction, viscosity, magnitude and intensity, vulnerability, resilience, prediction, forecasting, secondary hazard.