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Volcano Viewing
January 11, 2001

Popocatepetl explodes.

Something’s bubbling up in the Phillipines and scientists are keeping a close watch. It’s a volcano called Mayon that volcanologists say could lead to an evacuation of the surrounding areas. Just last month when the volcano Popocatepetl erupted in Mexico, tens of thousands of people had already been evacuated from much of the surrounding danger zone.

Scientists have been keeping a watchful eye on these potential disasters for a long time. An elaborate monitoring system now allows experts to get early warning of eruptions, and move people out of harm’s way.

Averting disaster

More than 300,000 people live in the danger zone under Popocatepetl (which means "smoking mountain" and is pronounced poh-poh-kah-TEH-peh-til). But the villages in the valleys around Popocatepetl turned into ghost towns in December. Residents were evacuated after Mexican scientists, who had been monitoring the volcano’s activity together with experts from the U.S., accurately predicted that it was about to erupt. When it began spewing molten rock on December 18, in what some scientists called its biggest explosion of the millennium, it came as no surprise.

This US Geological Survey video shows one of the hazards of volcanos: ashfall.
courtesy USGS

This situation is in stark contrast to volcanic disasters such as Mt. St. Helen’s in 1980 and the Nevado del Ruiz volcano in Columbia which killed more than 25,000 people when it erupted in 1985. "In essence—in those days anyway—our ability to actually forecast exactly what was going to happen and when it was going to happen was fairly primitive," says C. Dan Miller, chief of the Volcano Disaster Assistance Program (VDAP).

VDAP, the world’s only volcano crisis response team, was formed by the U.S. Geological Survey (USGS) and the Office of Foreign Disaster Assistance to try and prevent fatalities caused by unforeseen eruptions.

"Since the 1980 eruptions we have refined our hazard assessment techniques," says Miller. "We much better understand volcano hazardous events such as directed blasts and debris avalanches and how to mitigate them, and we have developed some very exciting new monitoring tools that allow us to do a much better job of predicting the onset of explosive eruptive activity."

Although not every eruption can be predicted even if the volcano is being monitored, Popocatepetl is not the only disaster to have been averted. In 1991, the VDAP team, working with scientists in the Philippines, was able to predict the eruption of Mt. Pinatubo in time for more than 75,000 people to be evacuated. The eruption was more than ten times larger than Mt. St. Helen’s, according to Miller.

Warning signs

Lava flow.
File size is 1 MB. Please be patient.
If you prefer to view the movie with RealPlayer, click here.

clip courtesy of the National Museum of Natural History

Scientists are able to tell when a volcano might erupt thanks to accurate and portable monitoring equipment that clues them in to the mountain’s inner workings. "Basically, for a volcanic eruption to occur magma, or molten lava, has to move from deep inside the crust of the earth to the surface," explains Miller. "And as this viscous material moves up through the crust it makes a lot of noise. It has to fracture and break rock in order to move toward the surface, and we recognize this noise in the form of earthquakes."

By placing a seismic monitoring network around the volcano, Miller and his team can locate the earthquakes and tell whether they are becoming shallower, thereby tracking the movement of the magma as it approaches the surface.

Besides causing earthquakes, the magma also causes bulging or swelling in the surface of the mountain by pushing aside rock as it moves toward the ground surface. Using deformation-monitoring equipment, scientists can measure this bulging, tracking the change in the shape of volcanoes over time.

Volcanoes aren’t all bad

No one can deny the devastating effect volcanoes have, but there is an upside to them as well. Over millions of years the breakdown of volcanic rock has yielded some of the most fertile soils on Earth. The geothermal energy they produced has been harnessed to produce electricity, and minerals such as copper, gold, silver, lead, and zinc come from magma found in extinct volcanoes. In fact, the Earth’s crust itself is mostly a by-product of once active volcanoes and magma that never erupted.

In addition, magma produces sulfur dioxide and carbon dioxide, so monitoring these gases also allows experts to chart the movement of the magma as it rises.

Modern technology has made it possible to process all of these measurements quickly and safely. "Because of the advent of the PC computer, we have very small, tidy, inexpensive monitoring systems that can gather real-time earthquake information, and we can locate an earthquake just a few seconds after it occurs," says Miller.

The Global Positioning System (GPS) also allows scientists to install equipment on the sides of the volcano that lets them monitor the situation from a safe location. "This is an important improvement because it means we can put out a number of these GPS stations and watch them move in three dimensions, but it doesn’t involve sending out a scientist and putting them in harm’s way," says Miller.

While it’s true that nothing can stop these fiery mountains from exploding at unpredictable intervals, at least now scientists have begun to develop techniques that can help keep the tragic loss of human life to a minimum.

Elsewhere on the Web

America’s volcanic past

Volcanoes of the World

The Smithsonian’s Global Volcanism Program

Volcanic Language

Volcano World

Principal types of volcanoes



by Jill Max


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