Predicting Eruptions

Warning Signs

Before an eruption, magma moves into the area beneath the volcano and collects in a magma chamber, or reservoir. As it comes closer to the surface, the magma releases gases. These events can offer valuable clues about the likelihood of an eruption. For example, the movement of magma produces small earthquakes and vibrations (seismicity). Magma gathering in a chamber causes slight swelling of the volcano's slopes. Gases released near the volcano can be measured for changes in quantity and makeup.

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 sulfur dioxide--a telltale gas that is released in increasing quantities before an eruption. Using these and other tools, it's possible to closely monitor activity at an awakening volcano.

The Problem of Prediction

Volcanologists are becoming very skilled at predicting the likelihood of an eruption. Still, a number of barriers remain. It's very difficult to pinpoint exactly when an eruption will happen. Often, moving magma doesn't result in an eruption, but instead cools below the surface. Monitoring potential eruptions is expensive. With many volcanoes erupting only every few hundred or thousand years, it's not possible to monitor every site. Volcanic eruptions don't occur without warning, however. If we set up monitoring devices, we should not be caught off guard by disastrous eruptions.