Volcanoes Loom as Sleeping Threat for Millions
for National Geographic News
|June 14, 2002|
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TV viewers around the world watched in horror last January as hundreds of thousands of Africans fled rivers of fiery lava that spewed down the slopes of Congo's Mount Nyiragongo and flooded the streets of Goma.
The vivid horror of that eruption, which killed about 75 people, was a stark reminder of the powerfuland often deadlyforces that lie beneath the surface of Earth's majestic volcanoes.
Researchers have estimated that more than one billion peopleapproximately 20 percent of the world's populationare living in volcanic hazard zones.
Experts expect the number to rise. The rapid growth of population, urbanization, and economic development are driving more and more people to settle around volcanoes, significantly increasing the potential loss of life and property in the event of eruptions, said Robert Tilling, a senior volcanologist with the U.S. Geological Survey's Volcano Hazards Program.
In this age of international air travel, even people not living in the vicinity of a volcano are at risk, he noted.
"In the last 20 years there have been at least 80 encounters between airliners and ash clouds, causing hundreds of millions of dollars in damage and lost revenue," said Tilling.
Every day, tens of thousands of passengers fly over volcanically active regions such as the North Pacific, which has more than 100 active volcanoes and four to five ash-producing eruptions each year.
A near-fatal accident in 1989 involving a 747 jetliner alerted authorities to the increasing dangers of drifting clouds of volcanic ash.
On December 15, 1989, a KLM flight carrying 231 passengers flew into a cloud of ash that had erupted from Alaska's Redoubt volcano and drifted 150 miles away. All four of the engines lost power and the plane dropped nearly two miles in altitude before the crew could restart the engines.
The plane sustained $80 million in damages. In 1995, an international network of Volcanic Ash Advisory Centers was established to counter the increasing threat.
Moving into Danger?
Figuring out how to reduce the hazards of volcanoes to people and property is not an easy task.
Volcanologists and public officials agree that monitoring is important, but it's expensive and not feasible for many countries. Emergency planning is also costly and complicated, especially when it involves evacuating huge numbers of people amid uncertain threats of volcanic eruption.
Despite major advances in technology in the last two decades, the ability to predict when a volcano might erupt remains elusive.
But meeting the challenge is imperative because volcanoes are "people magnets," said Christopher Small, a geophysicist at Columbia University's Lamont-Doherty Earth Observatory. "If you look at the settlement patterns in satellite imageryand you can actually see farms and townsthere are a surprising number of people living in the throat of Satan," he said.
Small and a colleague conducted a study that combined 1990 census data and satellite imagery to determine how many people live within volcanic hazard zones, or within 62 miles (100 kilometers) of a volcano. They identified 457 volcanoes where one million or more people live within that range. Many of the volcanoesseveral in Indonesia and Japan, for instancehave surrounding populations greatly exceeding one million.
Part of the problem is greater competition for land and an increase in urban migration that is swelling populations in previously unsettled volcanic regions.
The ash emitted by volcanic eruptions is rich in nutrients, making the soil highly fertile. "In tropical Java, people are farming right on the flanks of volcanoes," said Small.
But the pattern is not confined to developing countries.
"Volcanoes and their surrounding environment are beautiful places to live and work and recreate, and the number of people moving into volcanic hazard zones is increasing in post-industrial as well as developing countries," said C. Dan Miller, chief of the U.S. Geological Survey's Volcano Disaster Assistance Program.
He cited southern Italy as an example. "Vesuvius is perched right on the edge of Naples, and it has a 2,000-year history of eruptions," said Miller, "yet there are 3.75 million people living within 30 kilometers [18 miles] of the summit.
"What do they do if it starts erupting?" he said. "No one can imagine evacuating a city the size of Naples."
Moving people out of hazard zones is generally not an option, said Tilling. "Many of the land-use patterns are long established, and people just won't do it," he said. "The only thing you can do is have systematic volcano monitoring to detect the earliest departure from normal activity."
The Smithsonian Institution's Global Volcanism Program maintains a database with information about 1,500 volcanoes around the world that have been active in the last 10,000 yearsthe blink of an eye to geologists. At any given moment, nearly two dozen could be in an eruptive phase, according to William Rose, a geologist at Michigan Technological University.
Yet only about 20 volcanoes are adequately monitored, and fewer than a third are monitored at all, according to the USGS.
Improved monitoring technology and greater scientific understanding of how volcanoes operate are giving volcanologists and public officials better tools to guide hazard-reduction planning, but evaluating threats is frequently still a tough call.
"It could be weeks, months, or years from the time a volcano shows some activity to eruption," said Miller. "It may never erupt. Moving people out of the way for the big event in a timely process is still our biggest challenge."
Mexico City knows the problem well. The city, which has a population of more than 20 million, lies within 37 miles (60 kilometers) of the summit of Popocatépetl, which has erupted at least 15 times in the last 400 years.
The flanks and valleys surrounding "Popo" have been evacuated several times since 1994 in response to earthquakes and eruptions of volcanic ash and plumes of steam. Each time the mountain has settled down without a major eruption, although sporadic activity continued through 2001. Yet when, or if, a major eruption may occur next remains unknown.
Challenge of Protection
The socio-economic costs of ordering an evacuation are huge. People must be housed and fed, and the crowded conditions pose public health risks. Security against major looting may be required, and commerce grinds to a halt.
Scientists tracking active volcanoes walk a tightrope when advising public officials on the likelihood of an eruption.
"The interface between the scientists monitoring a volcano and public officials is very difficult," said Miller. "Most people are willing to be evacuated once. But if nothing happens, the loss of credibility could cause people to ignore future warnings."
Inadequate resources, poor coordination, and bureaucratic inertia or a failure to heed warnings can have tragic consequences.
Colombia's Nevado del Ruiz began showing signs of volcanic activity in November 1984. Volcanologists warned government officials that the town of Armero lay directly in the path of what in the past had been monumental mud flows. Yet no advance warning system or evacuation plans were developed.
The volcano erupted on November 13, 1985. Two and a half hours after the eruption began, a wall of mud, water, and debris burst through the canyon above Armero, killing more than 23,000 people.
When Nyiragongo erupted early this year in the Democratic Republic of the Congo, destroying 40 percent of the town, it was the volcano's second major eruption in 25 years.
Scientists had warned government officials in January that an eruption was imminent. But the war-torn government was unable to respond to the warnings and no emergency preparations were in place. An estimated 350,000 people fled to safety in neighboring Rwanda, where tens of thousands remain in refugee camps.
"Scientists can't make the decision to evacuate," said Miller. "We can provide information on the hazards, and we are working to do that. But using the informationlong-range land-use planning, development of early-warning systems, and evacuation plansthat's up to public officials."
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