Tectonic hazards: plates, margins and why depth matters
Earthquakes and volcanoes are not scattered at random. Learn the margins properly in week one and every case study afterwards becomes easier to explain.
Lesson overview
What you'll learn in this lesson
Explain tectonic and weather hazards, their effects and the management of risk in contrasting places.
Key learning points
- • Plate movement and the three margins
- • Primary and secondary effects
- • Why the same magnitude kills differently
- • Managing risk
This lesson at a glance
- 30 minutes
- 21 parts to scroll through
- 4 quick checks
- Marked quiz at the end
- Gentle pace: short sittings with pauses
Words to know
Scroll down — the lesson carries on below
Watch & discover
Part 1 of 21
Visual introductionPicture this
Tectonic hazards: plates, margins and why depth matters
Earthquakes and volcanoes are not scattered at random. Learn the margins properly in week one and every case study afterwards becomes easier to explain.
In a nutshell
Explain tectonic and weather hazards, their effects and the management of risk in contrasting places.
Learning cycle
Part 2 of 21
Learning cycle 1 of 2
Part 1 · Plate movement and the three margins
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 3 of 21
Learn
Plate movement and the three margins
Convection and slab pull drag the plates across the asthenosphere. At a destructive margin oceanic crust subducts beneath continental crust, generating deep earthquakes and explosive composite volcanoes. At a constructive margin plates separate, magma rises and shield volcanoes with runny basaltic lava form. At a conservative margin plates slide past one another; friction locks them, stress builds and releases as an earthquake — no volcano, because no magma reaches the surface.
Reset break
Part 4 of 21
Pause
That's sitting 1 of 5 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Explore the idea
Part 5 of 21
Learn
Primary and secondary effects
Primary effects happen at the moment of the event: buildings collapse, people are killed, roads fracture. Secondary effects follow from those: fire from ruptured gas mains, disease from broken water pipes, homelessness, lost income, tsunami. Exam answers lose marks by mixing the two, so label them explicitly.
Quick check
Part 6 of 21
Quick check
Part 7 of 21
Reset break
Part 8 of 21
Pause
That's sitting 2 of 5 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Learning cycle
Part 9 of 21
Learning cycle 2 of 2
Part 2 · Why the same magnitude kills differently
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 10 of 21
Learn
Why the same magnitude kills differently
A magnitude 7 event in a high-income country and in a low-income country produce very different death tolls. Building codes, emergency planning, hospital capacity, road access and the money to enforce regulation all change the outcome. Wealth is the underlying variable behind almost every contrast you will be asked to explain.
Explore the idea
Part 11 of 21
Learn
Managing risk
Four strategies recur: monitoring, prediction, protection and planning. Volcanoes can be monitored and, to a degree, predicted; earthquakes cannot be predicted reliably, so protection (aseismic design) and planning (drills, exclusion zones, insurance) carry more weight.
Reset break
Part 12 of 21
Pause
That's sitting 3 of 5 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Quick check
Part 13 of 21
Quick check
Part 14 of 21
Explore the idea
Part 15 of 21
Worked example
Model answer: 'Explain why effects differ between two contrasting areas of similar magnitude' (6 marks)
The magnitude of an event sets the energy released, but the effects depend on the vulnerability of the place. In a higher-income country, seismic building regulations mean frames flex rather than collapse, so primary effects such as deaths from building failure are reduced; well-funded emergency services also limit secondary effects, because fires are contained and water supplies restored quickly. In a lower-income country, informal housing built without reinforcement collapses under the same shaking, and limited hospital and road capacity means injuries become deaths and disease spreads through damaged sanitation. The difference in effects is therefore chiefly a difference in wealth and governance rather than in the hazard itself.
Reset break
Part 16 of 21
Pause
That's sitting 4 of 5 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Challenge round
Part 17 of 21
Game · Sort it
Which of these are true?
Drag each card into the right column. Tap a card first if dragging is fiddly.
True
Not true
Challenge round
Part 18 of 21
Game · Fill the gaps
Finish the sentences
Choose the word that belongs in each gap.
Primary ____ happen at the moment of the event: buildings collapse, people are killed, roads fracture.
Challenge round
Part 19 of 21
Game · Recall cards
Which margin produces explosive composite volcanoes?
Card 1 of 4
Mastery quiz
Part 20 of 21
Marked quiz
End of lesson quiz: Tectonic hazards: plates, margins and why depth matters
4 questions, marked with the reasoning shown. No timer.
1. Which margin produces explosive composite volcanoes?
2. Which is a secondary effect of an earthquake?
3. Why is no volcano found at a conservative margin?
4. Which management strategy is least reliable for earthquakes?
Lesson round-up
Part 21 of 21
Lesson round-up
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Ask LunaPart 1 of 21 · Watch & discover