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• A volcano is a hazard caused by plate tectonics.
• Volcanic eruptions have both primary effects (such as the destruction of buildings) and secondary effects (such as homelessness).
• There are ways of reducing the effects of volcanic eruptions by, for example, planning, predicting and preparing.

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A volcano is an opening in the Earth's crust. Ash, magma and gases escape from this opening. Volcanic eruptions can be a hazard to people and the environment.

Volcanoes occur either at the unstable boundaries of tectonic plates or in the middle of plates where the crust is thin or where there is a particularly hot spot in the mantle.

Find out more about tectonic plates.

Explore the different parts of a volcanic eruption using the diagram below.

A volcanic eruption can cause a variety of effects. These can be classed as primary or secondary effects. Primary effects are caused by the volcanic eruption whereas the secondary effects are caused by the primary effects.

• As the volcano erupts, streams of molten rock called lava flow from the volcano causing damage to habitats and property.
• Pyroclastic flows are flows of super-heated gas and ash. These can travel at hundreds of kilometres per hour.
• Ash fall from volcanoes can land on the roofs of buildings causing them to collapse.

• Volcanic eruptions can lead to climate change. Ash from volcanoes can reflect the sun’s energy and lead to cooling, the carbon dioxide released can contribute to global warming.
• Roads can become blocked by solidified lava flows making it difficult to travel around.
• There can be positive effects of volcanic eruptions. Ash from the volcano can act as a fertiliser for soils.

There are a number of reasons why people choose to live near volcanoes:

• Geothermal energy can be harnessed by using the steam from under the ground.
• Many people can visit the area, creating a tourism industry.
• The soil around volcanoes is rich in minerals and therefore creates excellent agricultural land.

After an eruption the country must respond. Some responses will happen very quickly (immediate responses) and some may go on for months or years (long-term responses).

Immediate responses

• Evacuating residents from the area is a priority following a volcanic eruption, or before, if an eruption has been predicted.
• Setting up exclusion zones, areas where people are not allowed to go, can help to reduce the number of deaths.
• Providing medical care to those injured.

Long term responses

• Rebuilding of damaged buildings and infrastructure must take place.
• Resettling people affected by the eruption. This may mean building new houses or even moving people to a whole new location.
• Installing monitoring equipment.

Play a Planet Planners mission and help to follow the disaster plans and restore normality after a volcanic eruption.

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Countries can try to reduce the risk of damage from volcanic eruptions by attempting to predict when they might occur, protecting their buildings and preparing their population for what to do in the event of an eruption. The extent to which a country can do this depends on their level of development. A high income country can spend more than a low income country meaning the effects would be reduced more.

Prediction

It is much easier to predict volcanic eruptions than earthquakes. Monitoring the area for seismic activity, changes in shape of the volcano and gas emissions can all help to predict when an eruption may occur.

Protection

There is little that can be done to protect buildings or land from a volcanic eruption but it may be possible to restrict what can be built in at-risk areas. For example, an area that is high-risk may have restrictions that do not allow the building of homes.

Preparation

By training people on what to do in the event of an evacuation people can prepare for an eruption. This may involve drills in schools or advising people to pack survival kits.