Maps and place knowledge, Year 10: earthquakes, eruptions and living with tectonic risk

A primary effect of a tectonic hazard

HintIt comes first, with nothing in between the event and the damage.

The whyDeaths and injuries from falling buildings, roads cracked by shaking and farmland buried by lava or ash are all immediate and direct. In an exam answer on your own case study, sort every effect into this group or the group of knock-on effects.

Secondary effects

HintThey are knock-on results, one step removed from the shaking.

The whyA knock-on effect happens because of the direct damage or the shaking, sometimes hours or weeks later. Fires from broken gas pipes, disease from dirty water, homelessness and lost jobs belong in the same group.

An immediate response to a hazard

HintThe name means 'straight away'.

The whyThe aim is to save lives and meet basic needs: rescue, first aid, food, clean water and shelter. Work that goes on for months and years afterwards, such as rebuilding homes and improving building rules, belongs in a different group.

The buildings, roads and businesses destroyed are worth more

HintCompare the price of what stands on each piece of ground.

The whyAn HIC has expensive property, factories, power stations and transport links, so the bill for the same shaking is larger. In a lower income country (LIC) the cost in money may be smaller, but it is often a bigger share of the country's wealth and far more lives are lost.

Broken water pipes and sewers, so drinking water is contaminated

HintThink about what runs under the streets and what happens when it cracks.

The whyCholera spreads through water polluted by sewage. When pipes burst and treatment works fail, people drink whatever water they can find. Crowded temporary camps make the spread faster. This is a classic secondary effect.

fertile

HintThe word describes ground that is rich in the minerals crops need.

The whyVolcanic rock and ash contain elements such as potassium and magnesium. As they weather, these are released into the soil. Harvests are good, so farming families have a strong reason to stay despite the danger.

Tourism provides jobs and income

HintThink of the guides, hotels, cafés and coach drivers.

The whyVisitors pay for places to stay, food, transport and tours, which supports the local economy. Volcanic areas can also offer geothermal energy and valuable minerals. For many people these benefits outweigh a risk that seems distant.

Rising magma gives warning signs that can be measured

HintSomething is on the move under the mountain before anything comes out.

The whyAs magma rises it causes many small earthquakes, makes the ground swell and releases more gas, especially sulfur dioxide. Instruments can record all three. Before an earthquake there is no reliable signal, so scientists can only give the probability of one in a region over a number of years.

A tiltmeter

HintIts name comes from a short verb meaning 'to lean'.

The whyRising magma makes a volcano swell like a slowly inflating balloon, so its sides become very slightly steeper. Recording that change, along with small earthquakes and gas emissions, helps scientists decide when to warn people to leave.

planning

HintIt is what you do when you work out in advance who goes where and when.

The whyThis strategy is about being ready: hazard maps that keep new building away from the most dangerous land, practised evacuation routes, drills in schools and workplaces, and stockpiles of food, water and medicine. It is cheap compared with engineering, so it matters most where money is short.