Predicting Volcanoes
It is very difficult to pinpoint the precise time of an imminent eruption. Moving magma does not always result in an eruption, cooling below the surface instead. Monitoring potential eruptions is expensive. With many volcanoes erupting only every few hundred or thousand years, it is impossible to ensure that every site is constantly monitored.

Volcanology can be a dangerous pursuit. Between 1979 and 2000, 23 volcanologists died while working on volcanoes. Yet without their efforts the science of predicting eruptions could not advance. As more and more people inhabit ‘hot spots’ around the world, advances are needed to avoid more fatalities (30,000 or so have occurred in the last 20 years).

Scientists can often find clues about past eruptions by analysing the deposits left behind. Areas affected by lava flows, debris flows, tephra, or pyroclastic flows can be mapped, making disaster planning for future eruption more effective. As well as this type of long-range forecasting, scientists are becoming more and more skilled at spotting the warning signs of an eruption.

Monitoring Methods
A number of tools can be used to record these warning signs. Seismographs can detect small earthquakes, while tiltmeters and geodimeters can measure the subtle swelling of a volcano. Correlation spectrometers (COSPECS) can measure amounts of sulphur dioxide - a telltale gas that is released in increasing quantities before an eruption.

1. Seismic Activity
Ground motions sensed by the seismometer are converted into electronic signals, which are transmitted by radio and are recorded on seismographs. There are four main types of seismograms: tectonic, volcanic, surface and tremor. Mapping the earthquake activity allows scientists to track the sub-surface movement of magma.

2. Tiltmeters
Electronic tiltmeters are highly sensitive instruments designed to detect minute changes in a volcano's shape. Unfortunately, this sensitivity makes electronic tiltmeters respond to signals that have nothing to do with volcanic processes- temperature. However, tiltmeters excel at imaging fast, short-term events that might otherwise pass unnoticed.

3. New Technologies
Radar satellites that continually orbit the earth can detect as little as a one-millimetre increase in swelling on the flanks of a volcano. Pioneering volcanologists are now flying to the summits of volcanoes in special helicopters, designed to withstand volcanic ash, in order to plant digital cameras on crater rims to keep an ongoing photographic diary of volcanic activity.

4. Anti-Disaster Research
For the first ever attempt to bore a hole into the core of a volcano, a structure like an oilrig has been built on the slopes of Japan's Mount Unzen. A slurry of water will be pumped into the drill shaft to cool the 700º C magma. By sampling the underground magma, scientists hope to find out more about the way volcanic gases build up and create explosions.