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Volcanic eruptions are unpredictable, however scientists can monitor volcanoes to try and estimate when they are likely to erupt. Scientists can use a variety of techniques to do this, such as:

• seismometers – used to measure earthquakes occurring near an eruption
• tiltmeters and global positioning systems (GPS) satellites – these devices monitor any changes in landscape, eg volcanoes tend to swell near an eruption
• thermal imaging – this allows a camera to monitor heat sources within the crust or volcano, it may help predict the onset of an eruption
• infrared camera imagery – these images can potentially show the magma chamber and any build-up of hot gases, steam or lava
• monitoring gases escaping from a volcano using robots called spiders – often there is an increased release of sulphur dioxide near an eruption as the magma gets closer to the surface
• measuring temperature – volcanoes become hotter when magma starts to rise through the main vent
• looking at previous eruptions – scientists can identify patterns of activity

Hazard mapping

Planning evacuation areas and removing the people most at risk from tectonic hazards is vital in reducing vulnerability. Hazard mapping allows local areas to limit access to the danger zones and prevent buildings near to potential hazards from being built. Exclusion zones can also be created, where no-one is allowed in them before, during or after an event.