YELLOWSTONE NATIONAL PARK, Wyo. - A sulfuric-smelling fog filled the November air, rising from bubbling pools on white terraces.
The scene looked like a witches' brew tucked inside a winter wonderland, one of thousands of reminders in Yellowstone National Park that the world's largest volcano breathes below the surface.
Chances are you've heard of the beast, the one capable of sending 2,000 times more matter into the sky than Mount St. Helens and producing an ash cloud stretching from Wyoming to the East Coast.
Nearly every major publication from the New York Times to National Geographic has written about it and the devastating impacts if it were to erupt.
But fears of a deadly blast might be overblown, according to some scientists. The Yellowstone volcano could even be dying. The last eruption, 70,000 years ago, was a relative poof compared with the climate-changing eruptions hundreds of thousands of years earlier.
Still, the debate over the volcano's potential reflects one enduring truth about Yellowstone and the geology beneath its surface: The park remains one of the foremost research laboratories in the world, drawing internationally renowned scientists studying everything from earthquakes to the origins of life to, yes, the power of that volcano lurking beneath the ground.
"Yellowstone is so over the top in so many ways it sometimes screams at you the answer that's happening other places," said Jacob Lowenstern, scientist in charge of the Yellowstone Volcano Observatory.
The fact that it could one day erupt again, covering the western U.S. in ash and molten rock, is simply another thing for scientists to study here.
WORLD'S LARGEST VOLCANO
In early November, a team of University of Wyoming researchers spread tarps on the snowy ground near white terraces outside Mammoth Hot Springs, where pools are stacked like small mountains filled with crystal-clear water.
"I have gotten radium out of that," said Ken Sims, a UW geology and geophysics professor and National Geographic explorer. "We should sample down there."
Sims knelt next to a mound of delicate formations and pulled machines out of boxes and backpacks: a radon detector with lights and a ticker-tape measurement recorder, a pH detector to record acid levels. Both would help him know how the water and gas interact.
"It looks like it's boiling," Sims said. "But it is actually from steam or CO2."
Sims was studying how fast water and gas mix as they rise to the surface. His research could ultimately help scientists understand what causes steam eruptions. If they know how fast steam and water interact in the park, they could better predict when an area will become more volatile.
It's one of dozens of projects he wants to try involving the volcano that could offer insights into the rest of the world, from the floors of oceans to the peaks of mountains.
The word volcano, though, seems ill-equipped to describe the 40-mile-long slush of molten rock and crystal under the nation's first national park.
Instead of a cone with a hole, the caldera is an interconnected maze of gas and water covering almost 60 miles of Wyoming's northwest corner, along with parts of Montana and Idaho.
More than 10,000 mud pots, boiling rivers and geysers act as nature's pressure-release valves, keeping the heated monster from exploding.
"The heat from the Yellowstone volcano is what drives the hydrothermal system," said Henry Heasler, the park's geologist. "It gets hot and rises, and the magma chamber, or reservoir, is at a relatively shallow depth."
The slush of magma starts about 5 miles into the Earth and extends down about another 6 miles, Lowenstern said.
That estimate changes as technology improves. Scientists can't simply X-ray the Earth's insides as they would a human's bones or organs. And because of its size and pressure, tentacles of water and gas extend miles away from the actual magma along fractures in the Earth's surface, creating features such as Mammoth Terraces and Boiling River.
Heasler tells schoolchildren on tours that Yellowstone is like the seven-book Harry Potter series and that scientists understand only the first paragraph of the first novel.
Sims believes that Yellowstone's rocks, its labyrinth of underground waterways and its volcano may hold clues that would help solve perhaps the greatest of science's mysteries.
The pull of the volcano's potential was so strong, in fact, that he moved from the prestigious Woods Hole Oceanographic Institution in Massachusetts to Laramie to be closer.
The UW professor and three other researchers recently applied for a nearly $3 million National Science Foundation grant to study the origin of life in Yellowstone.
It may seem lofty, but the group says an understanding of how life formed on this planet can be found only in a place where life exists in its most extreme environment.
"If you look at the evolutionary history of life and the metabolic functions that it uses, you can map back pretty much all of those functions to an origin in a hot environment," said Eric Boyd, a thermal biology professor at Montana State University who will work on the project. "Life likely emerged in a high-temperature environment, and then it diversified. It diversified to inhabit virtually every ecological niche on the face of the planet."
Which means that if you want to know where life came from, start looking in Yellowstone.
It wouldn't be the first discovery with worldwide implications originating in the park.
In the 1960s, researchers in the Lower Geyser Basin of Yellowstone found what is called Thermos aquaticus, a type of bacteria that can survive at temperatures far higher than anything most people expected at the time, said Everett Shock, a geochemist at Arizona State University who is working with Sims.
Scientists realized years later that they could use an enzyme in the organism to copy DNA at exponential rates because of high heat.
The result: an enzyme used in everything from AIDS diagnosis to DNA fingerprinting, a multibillion-dollar industry traced back to heat in Yellowstone's water, he said.
"Enormous things have happened because of this first innocent characterization of a microbe in a hot spring," he said. "No one went to Yellowstone thinking, 'I'm going to find an enzyme operating at high temperatures and revolutionize molecular biology.' "
WILL IT BLOW?
The most often-asked question, the one debated on blogs and volcano forums and end-of-the-world sites, is: When will it blow?
No one really knows the answer, and Lowenstern cautions that it may be if rather than when.
The Yellowstone volcano's first major eruption occurred 2.06 million years ago. A second eruption followed 1.3 million years ago and a third 640,000 years ago.
The series has led many to wonder whether it explodes about every 700,000 years, leaving the caldera primed for another blast.
Lowenstern, along with nearly all other scientists actively studying the volcano, says no. Three instances occurring at two intervals do not, statistically, mean anything.
The last eruption of any size was 70,000 years ago and was not nearly the magnitude of the three large eruptions, Lowenstern said.
Dozens of scientists around the United States will continue to monitor the volcano's behavior. They track the number and strength of earthquakes and record when the ground lifts even as little as a centimeter.
In mid-February, the Yellowstone Volcano Observatory said the ground near Norris Junction rose 3.5 centimeters during five months, an amount significant enough to report but not signaling potential catastrophe, Lowenstern said.
The observatory had to write a clarification soon after explaining that the movement was simply another change in a continually active system.
"When we work in a place that hasn't erupted in 70,000 years, you need to watch and wait and pay attention to what the Earth is saying," Lowenstern said.
While the Earth may still sputter and gurgle and spew, it might not ever erupt the way it has so many years ago.
"Yellowstone is the most recent system along the hot spot. There are older volcanic systems that march their way up the plains, and as they got older and older, all of those systems eventually cooled," Lowenstern said. "The ground subsided, and Hawaiian-type lava covered them up. Yellowstone will likely be a good place to grow potatoes one day."
And in the meantime, scientists like Sims, Heasler, Lowenstern and others will be there, watching, learning and waiting.