OCR A-Level Geography H481
Coastal Landscapes
Glaciated Landscapes
Dryland Landscapes
Earth’s Life Support Systems
Changing Spaces; Making Places
Trade in the Contemporary World
Global Migration
Human Rights
Power and Borders
Climate Change
Disease Dilemmas
Exploring Oceans
Future of Food
Hazardous Earth
Geographical Skills
Hazardous Earth
Earthquake-triggered landslides, avalanches and flooding
- 2 things to know
- Component 03
Overview
Recall questions on why shaking triggers landslides and which slopes fail, landslides in the 2008 Sichuan earthquake, landslide dams and how they are made safe, avalanches at Yungay in 1970 and after the 2015 Nepal earthquake, flooding from failed dams, levees and subsidence, and what makes a landslide a disaster.
What you need to know
Answer each one before you reveal it.
Which slope conditions make earthquake landslides most likely?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Why does shaking trigger landslides?
Model answer
The ground acceleration adds a horizontal force to the slope and momentarily reduces the friction holding the material in place, so the shear stress exceeds the shear strength and the slope fails.
- 2
Which slope conditions make earthquake landslides most likely?
Model answer
Steep slopes of weathered rock or loose regolith, especially where they are already saturated by heavy rain.
- 3
Why can landslides kill more people than the shaking itself in mountainous regions?
Model answer
Settlements are confined to valley floors beneath unstable slopes, so a landslide can bury a whole village in seconds and cut the roads needed to reach it.
- 4
What happened in Sichuan, China, in 2008 that illustrates the landslide hazard?
Model answer
A magnitude 7.9 earthquake set off tens of thousands of landslides across the mountains, burying settlements, blocking roads and damming rivers.
- 5
What is a landslide dam, and why is it dangerous?
Model answer
A barrier of debris that blocks a river and impounds a lake behind it; the loose dam can fail suddenly and release a destructive flood downstream.
- 6
How are landslide dams usually made safe?
Model answer
Engineers cut a controlled spillway across the debris so that the lake drains steadily instead of bursting through.
Other ways to work this
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