A world unready for its own hazards.

A world unready for its own hazards

The threat of nuclear war and other nightmares that humans could bring upon themselves have weighed heavily on the public mind for years. But the recent Mexican earthquake (SN: 9/28/85, p. 196) and the volcanic eruption of Nevado del Ruiz in Colombia (SN: 11/23/85, p. 326), each of which killed thousands of people, graphically remind us that nature possesses a violence of its own. Moreover, embedded in the geological record is evidence for mass extinctions that may have been caused by the impacts of asteroids or comets with energies several thousand times greater than the nuclear arsenal, and for volcanoes that erupted with a fury far exceeding any volcanic eruption in historic times.

The message of University of Chicago geologist Joseph V. Smith and other earth scientists is that, while there have been many improvements in geoscience and technology, "the earth is still flying blind' when it comes to recognizing and planning for natural hazards. Smith is rallying for an International Decade for Hazard Reduction, first proposed in 1984 by Frank Press, president of the National Academy of Sciences. In Baltimore last week, at a special session of the American Geophysical Union meeting, he and other scientists discussed the threats of earthquakes, volcanoes, asteroids and comets. A future session will focus on hazards from storms.

Hazards have been assessed in at least 12 countries for more than 30 volcanoes, according to C. Dan Miller at the U.S. Geological Survey (USGS) Cascades Volcano Observatory in Vancouver, Wash. But as Smith notes, more than 800 volcanoes in the world are potentially dangerous. For small to moderate-sized eruptions, says Miller, the technology now exists to monitor and assess these hazards. "But the problem is that we don't have the money to implement them,' especially in developing countries, he says.

Even when the scientific work has been done, there are communication problems among scientists, the public and officials, notes Robert W. Decker at USGS in Menlo Park, Calif. "If [your warning] fails, you don't want someone to say you cried wolf, because you didn't, he says. "The wolf was there; he just wasn't hungry.'

Cataclysmic eruptions, which occur on average about every 500,000 years and spew out as much as several thousand cubic kilometers of magma, are also a certainty for the future, says Miller. The effects of these events have not been well studied, but Miller notes that their ejected sulfate aerosols could produce "volcanic winters,' which, like "nuclear winters,' would severely affect climate and food production for years. Since the world has enough food in storage to last only about 70 days, Miller and Smith urge that scientists and policymakers explore the scientific, economic and social issues revolving around the stockpiling of food.

Perhaps the most violent but least likely natural event would be a collision with a large asteroid. Eugene M. Shoemaker of the USGS in Flagstaff, Ariz., and Alan W. Harris of the Jet Propulsion Laboratory in Pasadena, Calif., estimate that the chances of an asteroid 0.5 kilometers in diameter hitting the earth in the next century are about 1 in 1,000. Such an asteroid could be detected decades before impact, they say, leaving some time for evacuating the target area or perhaps for deflecting the asteroid's orbit or breaking it up in space.

"In my mind, the most significant hazard is . . . from smaller bodies whose dimensions are about 10 to 20 meters and which enter the earth's atmosphere once every few decades,' says Shoemaker. These meteoric fireballs would not reach the ground, but would deposit into the atmosphere energies equivalent to 1 to 10 megatons of TNT. Shoemaker's and Harris's greatest fear is that the resulting blast would be mistaken by less technologically savvy countries as a nuclear explosion and trigger the more violent action of humans.