Scientists analyze volcanoes’ killing ways

An analysis of people’s deaths from more than 400 volcanic eruptions may help reduce fatalities from future eruptions.

Pyroclastic flows spill down the slopes of Mayon volcano in the Philippines in this Sept. 23, 1984, image. Because more than 73,000 people evacuated danger zones, this eruption claimed no casualties. C.G. Newhall/U.S. Geol. Survey

In recorded history, volcanic activity has killed about 275,000 people, estimates Tom Simkin, a geologist with the National Museum of Natural History in Washington, D.C. He and his colleagues report their findings in the Jan. 12 Science.

The trends are troubling. Each of the past 3 centuries has shown a doubling of fatal volcanic eruptions, and recent decades have averaged around three deadly eruptions per year. Much of this increase is due to population growth, the scientists say, because volcanic activity has remained roughly constant throughout recent centuries.

Pyroclastic flows—hot clouds of ash that sweep down the volcano at hurricane speeds—are the predominant killer, claiming almost 80,000 victims, the team reports. Volcano-triggered tsunamis, a threat to those living along the ocean even hundreds of miles away from an eruption, have drowned about 55,000. Also among the major killers are mudflows and tephra—the ash, rocks, and other material thrown skyward by volcanoes.

Although many deaths occur in the first 24 hours of an eruption, when the element of surprise is the strongest, the researchers found that nearly two-thirds occurred more than a month after the eruption began. While thousands succumbed to indirect consequences of eruptions such as famines, many others who returned to the danger zone died in landslides or renewed volcanic activity.

Simkin says more public education about these longer-term dangers of eruptions and increased attention to lava and smothering gases such as carbon dioxide could help stem risks to growing populations near volcanoes. Scientists can combine information about patterns of past volcanic behavior with sophisticated surveillance that uses satellites and earthbound instruments to better understand volcanoes and to provide warnings, says Jonathan H. Fink, a volcanologist at Arizona State University in Tempe.

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