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
Predicting, monitoring and managing volcanic hazards
- 1 thing to know
- Component 03
Overview
Recall questions on why eruptions can be forecast, earthquake swarms, harmonic tremor, tiltmeters, satellite radar and gas monitoring, hazard maps and exclusion zones, mitigating the event by diverting lava at Heimaey and on Mount Etna, sabo dams, mitigating vulnerability and losses, community preparedness, and careful evacuation warnings.
What you need to know
Answer each one before you reveal it.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Why is a volcanic eruption easier to forecast than an earthquake?
Model answer
Magma moving towards the surface produces measurable warning signs over days to months, whereas strain building on a fault gives no reliable precursor.
- 2
What does a swarm of small earthquakes beneath a volcano indicate?
Model answer
That magma is forcing its way upwards and fracturing the rock, which is one of the clearest signs that an eruption may be approaching.
- 3
What is harmonic tremor, and what does it show?
Model answer
A continuous rhythmic vibration rather than a sharp shock, produced by magma and gas moving through the plumbing of the volcano.
- 4
How do tiltmeters help to forecast an eruption?
Model answer
They detect the slight swelling of the volcano's flanks as the magma chamber fills, measuring changes in slope far too small to see.
- 5
How is satellite radar used to monitor volcanoes?
Model answer
Repeated radar images of the same ground are compared to map centimetre-scale inflation or deflation across the whole edifice, without anyone having to visit it.
- 6
What does a rise in sulphur dioxide emission from a volcano suggest?
Model answer
That fresh, gas-rich magma has risen close enough to the surface for its gas to escape, which often precedes an eruption.
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