Living with tectonic hazards

Why do people live with the risk?

Millions of people live near volcanoes or on fault lines. Why?

Fertile soil: volcanic ash breaks down into rich soil. Farmers grow grapes, olives and citrus on the slopes of Mount Etna in Sicily.
heat from underground can make electricity and heat homes. Most homes in Iceland are heated by geothermal energy.
volcanoes, hot springs and geysers attract visitors and create jobs.
Minerals: volcanic areas can be rich in metals and other minerals to mine.
Jobs and cities: big cities on fault lines, such as Tokyo, Kathmandu and San Francisco, offer jobs and services.
Home and family: people don't want to leave their home and community, or can't afford to move.
Low perceived risk: big eruptions and earthquakes are rare, and people may trust buildings and warnings to keep them safe.

Key terms

Reducing the risk

We can't stop earthquakes or eruptions, but we can reduce their effects.

Remember

The four Ps: , , and .

Monitoring means watching for warning signs, using scientific equipment.
Prediction means using that information to forecast when and where a hazard will happen.
Protection means designing buildings and defences to withstand a hazard.
Planning means organising where people live and what they do in an emergency.

Key terms

Monitoring and prediction

Volcanoes give warning signs before they erupt, which scientists monitor:

Seismometers detect small earthquakes as magma rises.
Tiltmeters and satellites detect the ground swelling.
Gas sensors detect rising levels of gases such as sulphur dioxide.

Example: in 1991, scientists monitoring Mount Pinatubo in the Philippines forecast a huge eruption. Tens of thousands of people were evacuated before it erupted, and the US Geological Survey and Philippine scientists estimated that at least 5,000 lives were saved.

Earthquakes can't yet be predicted. Scientists know which places are at risk, and how often big earthquakes have happened there, but not exactly when the next one will strike.

Common mistake

Don't say scientists can predict earthquakes. They can forecast volcanic eruptions and map where earthquakes are likely.

Protection and planning

Earthquake-resistant buildings: deep foundations, steel frames, cross-bracing, and rubber shock absorbers in the foundations that let a building sway without collapsing. Chile's strict building codes are one reason fewer people died there in 2010.
and tsunami barriers along coasts at risk.

Hazard maps show the most dangerous areas, so building there can be limited.
, emergency supplies and shelters are prepared in advance.
Drills and education: in Japan, schools and businesses practise every year on Disaster Prevention Day, 1 September, the anniversary of the 1923 Great Kantō earthquake.

Judgement: protection and planning save the most lives in the long run, but they cost money, which is why poorer countries remain more vulnerable.

Exam practice

Plan your own answer first, then open the model answers to see what each level looks like.

9 marks · about 9 minutes

Assess how far monitoring, prediction, protection and planning can reduce the effects of tectonic hazards.

Assess means: Weigh up how important or successful something is, then make a judgement.

Link it

Use the facts from:

Chile 2010 and Nepal 2015 earthquakes (Maule, Chile, and Gorkha, Nepal, 27 February 2010 and 25 April 2015)

Level 1 (Basic)· 3/9 marks (band 1–3)

Monitoring can tell people when a volcano will erupt so they can leave. Strong buildings stop them falling down in earthquakes. Planning helps people know what to do.

Why this level: Three of the four Ps are described, but simply, with no examples and no judgement of how far they work. To reach Level 2: use named examples and explain how each one reduces the effects.

Level 2 (Clear)· 5/9 marks (band 4–6)

Monitoring volcanoes can save lives. Seismometers and gas sensors gave warning before Mount Pinatubo erupted in 1991, so tens of thousands of people were evacuated and at least 5,000 lives were saved. Protection, such as earthquake-resistant buildings, helps too: Chile's strict building codes are one reason why fewer people died there in 2010 than in Nepal in 2015. Planning, such as drills in Japan, teaches people what to do.

Why this level: Clear explanations with good examples, but it doesn't assess limits (earthquakes can't be predicted; cost), so there is no balanced judgement. To reach Level 3: weigh up where the four Ps work less well, then make a judgement.

Level 3 (Detailed)· 8/9 marks (band 7–9)

Monitoring and prediction can greatly reduce the effects of volcanic eruptions, because volcanoes give warning signs. At Mount Pinatubo in 1991, scientists detected small earthquakes and rising gases, so tens of thousands of people were evacuated and at least 5,000 lives were saved. However, earthquakes can't yet be predicted, so for them protection matters more. Chile's strict building codes are one reason why its magnitude 8.8 earthquake in 2010 killed about 520 people, while Nepal's weaker 2015 earthquake killed over 8,790. Planning also helps: in Japan, yearly drills mean people know to take cover and evacuate quickly. Yet all four Ps cost money. Seismometers, resistant buildings and drills are hard for poorer countries such as Nepal to afford, so the people most at risk often benefit least. Overall, the four Ps can reduce effects a great deal, especially deaths, but how far depends on the type of hazard and on whether a country can afford them.

Why this level: Detailed, accurate examples for each P, with limits weighed (earthquakes can't be predicted; cost for poorer countries) and a reasoned judgement that answers "how far". This is Level 3.

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