for National Geographic News
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?
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