rocks + hot gas = danger
Seattle, for example, lies within destructive range of Mount Rainier. But that's chump change compared to El Popocatepetl. The giant volcano is visible on the skyline of Mexico City -- the world's largest metropolis, and about 30 million people live nearby.
Thus, while volcanologists are fascinated by hot lava -- and who wouldn't be? -- they are also obsessed with better volcano forecasts. Accurate forecasts of eruptions would allow prompt evacuation when necessary. Bogus warnings, on the other hand, cause havoc and make people less likely to heed the next warning. Today's eruption predictions rely on the earthquakes sparked by the rise of magma (molten, underground rock) inside a volcano. To improve those warnings, volcanologist Stanley Williams of Arizona State University studies gases -- rather than quakes -- released from rising magma. In volcanoes, as in soda bottles, gas is released when the pressure drops -- except that it's a bit more dramatic: Williams says the violent release of gas is what powers many explosive eruptions.
While you can safely measure earthquakes using seismometers that relay data via radio, measuring gas is tougher. One major gas, sulfur dioxide, can be measured with equipment designed to remotely monitor smokestack pollution. But measuring carbon dioxide, the predominant gas released in eruptions, might provide better clues to incipient eruptions, once someone figures out how to measure it.
the danger zone
Nevertheless, the scientists had taken the usual precautions -- radios, fireproof suits and helmets -- before climbing to retrieve gas samples from the cone. And that was just as well: "With a few seconds warning," Williams says, "it blew up, more powerful than anything before it."
Within a second, he says, six scientists were dead, and several were severely injured. "I was barely alive, had a hole knocked in my head, both legs broken," he recalls. Fortunately, a Colombian grad student named Marta Calvache hustled up to help the disoriented survivors, and she and others carried Williams in a blanket to safety.
The volcano was a hell on Earth, with hot, sharp flying rocks and gas up to 700° to 800° C -- hotter than molten lead. Those extreme conditions, Williams says, were "part of the reason that [the bodies of four scientists] were not found -- the rocks and gas just vaporized them."
Although Williams continues studying volcanoes, he's become more cautious. His wardrobe runs to the best helmets and fire-resistant clothing money can buy, and he's still trying to perfect remote sensors for carbon dioxide.
Leaving radio-transmitting carbon-dioxide sensors near a volcano seems a logical solution to the problem, he says, but the hot, acidic environment is almost as hard on equipment as it is on people. (See Why Files coverage of volcanoes, or an update on predictions at Mt. St. Helens.)
Dangerous natural forces may also be microscopic.
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