Sims is 50 years old, an avid rock climber and former professional mountain guide. He doesn't like cities; he's allergic to crowds. He dresses as if life were one long camping trip. A professor at the University of Wyoming, he lives in Laramie with his wife and two young children. He hasn't owned a TV set in 25 years. Volcano science has never been a safe occupation—more than 20 scientists have died on volcanoes in the past 30 years. Sims carries a scar on his right arm from Sicily's Mount Etna, where his shirt melted into his skin. He's even-tempered and analytical and seemingly never off duty. He once wrote a paper on a restaurant tablecloth, scribbling until 3 a.m. Then he took the tablecloth home.
Tedesco, 51, is fiery and fashion conscious, an inexperienced alpinist and an unrepentant epicure. On the Nyiragongo expedition, where every ounce hauled up the mountain was carefully considered, Tedesco brought a large glass bottle of extra virgin olive oil. He lives with his wife, teenage daughter, five cats, and three dogs just outside Rome and is a professor at the Second University of Naples. When he speaks of Nyiragongo, he drops all pretense of scholarly dispassion. "It's no secret that I love Goma," he says. "My greatest fear is to make a big mistake—not to predict an eruption."
Sims led the descent into the crater, anchoring ropes and spidering down walls. The rest of the party followed. Nyiragongo is in the Great Rift Valley, where the African continental plate is being wrenched apart, and microquakes constantly shake the volcano. Pebbles clattered down walls. Town-house-size rocks wobbled like loose teeth. The mountain seemed ready to collapse.
The team set up camp on a wide ledge 800 feet below the rim, a few hundred feet above the thundering lake. The ledge was covered with heavy ash, called tephra, and speckled with droplets of volcanic glass and delicate lava threads known as Pele's hair. The surface was warm; hiking pants left on a tent floor had a fresh-from-the-dryer feel in the morning.
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 environment was noxious, the air full of acid and metallic aerosol particles. Raindrops sizzled as they landed in fumaroles. Gas masks were worn. Within days, zipper pulls corroded; camera lenses began disintegrating. Sims handed out throat lozenges.
Here on this ledge Tedesco and Sims began working with the field lab they'd brought. A blue padded case held what Tedesco called a "gas sniffer" to measure carbon dioxide, carbon monoxide, and methane. A shoe-box-size RAD7 tested for radon. A vacuum pump, housed in a rusty ammo box, captured a fumarole's plume.
Why measure gas? Because volcanoes are gas-driven machines. An eruption is often preceded by an increase in discharged gas and by variations in its chemical composition. The rise of magma, its accumulation in chambers, its propulsion into fractures—these events produce chemical signals that reach the surface well ahead of the magma itself.
Sims uses radioactive clocks to decipher volcanic processes, measuring and comparing two isotopes of radon. By tracking this ratio over time, he can determine how long gas has taken to reach the surface and gain clues to the chemical, thermal, and mechanical state of the rocks the gas is passing through. But few conclusions can be derived from a single expedition. Only long-term studies can determine which type of gas fluctuations are cause for alarm and which are part of the volcano's normal cycles. Until top scientists make regular visits—something Tedesco has been desperately urging—the best that can be done is to maintain a precise record of Nyiragongo's every move.
That task falls to the Goma Volcanic Observatory, located in a dilapidated one-story building in the city center and staffed around the clock. Katcho Karume, 44, the observatory's director general, has a Ph.D. in environmental physics. "Seismology is the heart of what we do," he said. Swarms of tremors are usually, though not always, a sign that an eruption is coming. But many of the observatory's seismic stations on Nyiragongo's slopes were looted during the wars. "For batteries," said Karume, shaking his head at the thought that Goma's population could be decimated for a few dollars' worth of batteries.
"You know, I hardly sleep," said Karume. "One million people depend on us." Without modern equipment, which could cost two million dollars—a daunting sum in one of the poorest nations in the world—an accurate forecast might not be possible. And even if the observatory were able to predict an eruption, then what?
"There is an emergency plan," insisted Feller Lutaichirwa, vice governor of North Kivu Province. Warning flags at stations throughout town, he said, announce the risk level of an eruption, from green, indicating low danger, to red, meaning an eruption is imminent.
Others begged to differ. "There is no plan," said journalist Horeb Bulambo. "And the flags are old." He was right. At most of the stations I saw, every flag had faded to white. Esteban Sacco, who until recently operated Goma's United Nations humanitarian affairs office, mentioned that only one road leads out of the city away from the volcano. "Within a couple of hours the whole town will be stuck," he said. "Imagine the worst."
Meanwhile, people continue to live on top of the lava. "I saw the eruption in 1977 and again in 2002," said Ignace Madingo, administrative secretary of the city district closest to the volcano. Both times he fled with his family, and both times his house disappeared. "Many people from this area died," he said. "The lava turned them into stones. You can't imagine. You never see them again. No trace." Today his land is a pile of jagged volcanic rocks. "We know the mountain will erupt again. Lava will come. Our houses will burn. And after, we will build once more."
To prevent a catastrophe, Sims believes, we must gain a deeper understanding of Nyiragongo. For starters, one crucial source of information is what's known as a zero-age sample: a chunk of lava fresh from the lake. It would be the Rosetta stone of Nyiragongo, the piece that could unlock the mountain's story, allowing every other rock to be accurately dated. "Ultimately it could lead to better eruptive predictions," Sims said.
Sims wanted that lava chunk. But he knew retrieval would be dangerous, and he struggled with the decision. He thought of his family; he fretted over lava bombs and rockfalls. He would never allow one of his own students to risk his or her life for such a sample. Yet he also understood that he was one of only a few people with both the climbing skills and scientific knowledge to get exactly what he wanted.
So he rappelled into the heart of the volcano. Standing on the crater floor, he couldn't see the lake itself, which was above him within the cone of cooled lava. But he could hear its hissing gases and smell its acrid fumes. He pulled on a silver-colored thermal suit, like a full-body oven mitt, so rigid he couldn't bend over to tie his shoes.
As he approached the spatter cone, the lava crunched like eggshells beneath his feet. The rim was 40 feet high, the wall nearly vertical, requiring rock-climbing skills to ascend. He started up, stretching for handholds and foot placements, drenched in sweat inside the suit. When he was ten feet from the top, spotters described to him over the radio the level of the lava, where it was exploding, where it was spilling over. Conditions changed by the minute. He was five feet away. Then three. Suddenly his foot slipped, and he smelled burning rubber. Looking down, he saw his shoe melting out from under him.
But he kept going. He peeked over the top, eye to eye with the boiling lava. This was beyond science. This was personal, the culmination of a lifetime of exploration and adventure and tireless curiosity. Over the radio the emotion in his voice was palpable. "Amazing. Incredible. I'll never see anything like this again."
After a few seconds he backed away. There was still essential work to do. He didn't have a hammer, so with a hard slam of his fist he broke off a piece of fresh lava. It was shiny, iridescent black, and so hot that, even wearing thermal gloves, he juggled it from hand to hand.
But he had it. The zero-age sample. Through a war zone, up a mountain, down a crater, to the edge of a lava lake, he had it. Now the science, at long last, could begin.