Deformation and seismic activity are two of the three key sets of data that scientists rely on to make predictions about volcanoes. Advances also have come in the third set, volcanic gases.

Now scientists can fly over a volcano and take repeated samples of such gases, and even use GPS systems to track the flight so that computers can provide important details on changes in gas levels and concentration.

Also, scientists can use microphones to measure noise from shifting rock and video cameras to constantly monitor areas that otherwise could be inspected only periodically.

The most important change, however, is the improvement in telemetry, or the transmission of data from various remote control instruments by radio, microwave or even cell phones.

“There was essentially no way in 1980 to do anything remotely

Preparing
In recent years, with the eruptions of Mount St. Helens and Mount Pinatubo many advances have been made in the study of volcanoes particularily in eruption prediction. The problem with volcanoes is that, though there may be similarities between volcanoes, every volcano behaves differently and has its own set of hazards. That is why it's important for scientists to study and monitor volcanoes. Many active volcanoes near populated areas have not been sufficiently studied to assess risk.

By studying volcanic deposits, scientists can produce hazard maps. These maps indicate the types of hazards that can be expected in a given area the next time a volcano erupts. Dating of these volcanic deposits helps determine how often an eruption may occur and the probability of an eruption each year. Monitoring of a volcano over long periods of time will indicate changes in the volcano before it erupts. These changes can help in predicting when an eruption may occur.

There are thought to be about 600 million people living close enough to active volcanoes to be affected when they erupt. Casualties from volcanic eruptions have been modest (around 300,000 in the last 200 years) compared to other natural hazards, but economic losses and societal disruption can be considerable

New approaches to volcanic hazard assessment and risk management are emerging as society requires more information to respond to volcanic emergencies.

The Federal Aviation Administration monitors volcano eruptions to prevent planes from traveling in areas with possible ash particles in the air due to the dangers of loss of visibility and possible engine failure.

After eruptions
After a volcano erupts, gases are released into the atmosphere. These gases include water vapor as well as carbon dioxide, sulfur dioxide, hydrogen sulfide, carbon monoxide, hydrogen gas and methane. All of these gases can form acid rain in high concentrations.

Ash particles impede air traffic as well as create immense breathing difficulties for people living near an erupting volcano. After a volcano, these 2-mm or smaller ash particles fly