Lake Kivu Basin
© National Geographic

When will Nyiragongo erupt? Nyiragongo is a two-mile-high volcano towering over the eastern edge of the Democratic Republic of the Congo (DRC) - one of the most active volcanoes on the planet and also one of the least studied. Two million people would be affected by a potential eruption of the volcano or the neighboring lake.

According to Tedesco, there is no question the volcano will erupt again, potentially transforming Goma into a modern Pompeii. "Goma," he says, "is the most dangerous city in the world." At the base of the volcano sprawls the city of Goma, growing by the day as villagers from the countryside seek refuge from rebel and government forces.

An estimated million people are now crammed into Goma. Twice in recent years Nyiragongo's eruptions have sent molten rock flowing toward the city. In 1977 lava raced down the mountain at more than 60 miles an hour, the fastest ever observed.

Several hundred people died, even though the flow had hardened before it reached the main part of the city. In 2002 the volcano shot more than 15 million cubic yards of lava into downtown Goma, destroying 14,000 homes, burying buildings to the top of the first floor, and forcing 350,000 citizens to flee.

Both eruptions were mere grumbles, though, compared with the fury Nyiragongo is thought capable of unleashing. Lake Kivu is 700 feet across - one of the largest in the world - with a mesmerizing kaleidoscopic surface. Black plates are cut by jagged cracks of orange, violently shifting and roiling. The lake roars like a jet plane taking off and emitted a thick white plume of dozens of deadly gases.

"The whole periodic table is churning in there," said U.S. volcanologist Ken Sims. The lake seemed to breathe, expanding and contracting, rising and falling, its surface level changing several feet in a matter of minutes, spectacular and terrifying at once. Every day the lava lake emits around 7,000 tons of sulfur dioxide, the chief element in acid rain. This is more than the total from every car and factory in the United States. "Basically, it's one big chimney," Tedesco said. The air is noxious and smells of acid. The fumes corrode everything metallic. This whole area is a ticking time-bomb primed to go off.

Source: National Geographic