Tectonic Hazards

GeographyAQAGCSEUnit: The Challenge of Natural Hazards
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The basics

The Earthquake That Should Have Killed Thousands

🌋 The Earthquake That Should Have Killed Thousands

On 27 February 2010, the ground shook for nearly three minutes along the Chilean coast. At magnitude 8.8, it was one of the most powerful earthquakes ever recorded in human history — releasing roughly 500 times more energy than the bomb dropped on Hiroshima. The sea pulled back from the shore, then surged back as a tsunami. Half a million homes were damaged or destroyed. Yet fewer than 600 people died.

Five years later, on 25 April 2015, a much weaker earthquake — magnitude 7.8 — struck Nepal. Buildings collapsed across the Kathmandu Valley. Ancient temples that had stood for five centuries crumbled in seconds. Around 9,000 people were killed and 2.8 million were made homeless. In the remote mountain villages, rescue teams could not reach survivors for three days.

Chile's earthquake was 32 times more powerful. Nepal's killed 16 times more people. Why the difference? The answer is not geology — it is wealth, governance, and the choices societies make before disaster strikes.

What is a plate margin?: The boundary where two tectonic plates meet.
Key terms

Geography glossary

What is a plate margin?
The boundary where two tectonic plates meet.
Spotlight
How Tectonic Hazards Form

The Earth's outermost layer — the lithosphere — is not a single solid shell. It is broken into roughly 12 large tectonic plates and several smaller ones, all moving slowly across the surface of the planet. This movement is driven by convection currents in the semi-molten mantle below: hot rock rises, spreads outward, c

Exam tip

Earn the mark scheme marks

🧠 Exam Framework: CLEVER

Use this framework to structure any tectonic hazard answer, especially comparisons between two countries:

C — Context and Causes — What type of plate margin? Why does the hazard occur here? (Chile: Nazca subducting beneath South American Plate. Nepal: Indian colliding with Eurasian Plate.)
L — Location details — Where exactly? Magnitude? Depth of focus? Urban or rural? Proximity to coast (tsunami risk)?
E — Effects (primary and secondary) — Immediate: deaths, buildings destroyed, infrastructure damage. Delayed: fires, disease, economic disruption, landslides, aftershocks.
V — Vulnerability factors — Why was this place more or less able to cope? Building quality, wealth, terrain, governance, population density.
E — Emergency response — How quickly did help arrive? What were the barriers? National vs international response?
R — Rebuilding and recovery — How long did it take? Was it effective? What was improved for the future?

For plate margin types, use: D.C.C.

  • Destructive — subduction — earthquakes AND volcanoes (Chile)
  • Collision — crumpling — earthquakes ONLY (Nepal / Himalayas)
  • Conservative — sliding — earthquakes ONLY (San Andreas Fault)
  • (Constructive — pulling apart — mild earthquakes + shield volcanoes)

Now try it yourself

Quiz · Question 1 of 18

At which type of plate margin do two plates move towards each other, causing one to be forced beneath the other?

Tap an answer to check it

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