Scientists can often find clues about past eruptions by studying the deposits left
behind. Areas affected by lava flows, debris flows, tephra, or pyroclastic flows can be mapped, making disaster planning more
effective. In addition to this type of long-range forecasting, scientists are becoming more and more skilled at spotting the
warning signs of an eruption.
Warning Signs :
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 :
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 :
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.