Steamboat Geyser, the tallest active geyser in the world, erupted more times in 2019 than in any other year, baffling scientists who are trying to understand what triggered this unusual streak of activity.
The geyser can shoot water more than 300 feet into the air, and this year it has erupted more than 45 times, surpassing the 32 eruptions recorded in 2018.
In the three years before that, however, the geyser didn't erupt at all. Unlike Old Faithful, which is famous for its highly predictable eruptions, Steamboat is an erratic giant.
"In the 1960s, there was another period where there were more than 20 eruptions per year," says Erin White, Yellowstone National Park's hydrologist. "Prior to that, there were dormant periods of more than 50 years."
She has stood right next to Steamboat as it was venting steam. "It is incredibly powerful," White says. "It's like standing next to a jet engine."
Steamboat's reawakening is an opportunity for researchers to try to answer some fundamental questions about how geysers work.
"It's such a big geyser. And the bigger something is, the easier it is to study," says Michael Manga of the University of California, Berkeley. "But it also captures people's imagination. When it got active again there was lots of press and it reminded people that there are fundamental things about the Earth we don't understand."
Geysers are relatively rare — the planet has fewer than 1,000, and about half of them are in Yellowstone.
And not many people study these erupting hot springs. The geyser scientific community "is a community of almost nobody," Manga says.
A couple of years ago, when he and a colleague wrote a review of geyser research for a science journal, "we could cite just about every paper ever written about geysers. And there's very few fields where you can do that."
Researchers do know the basic ingredients needed for a geyser, White says.
"You need to have a source of water, you need a source of heat, and you need a structure, a geologic structure, that is constrained or confined in some way to develop pressure that will generate an eruption," she says.
Yellowstone is a seismically active place, and it's possible that the reactivation of Steamboat was somehow related to the Maple Creek earthquake swarm in 2017, says Yellowstone National Park geologist Jeff Hungerford.
"Steamboat is in the Norris geyser basin, and the Norris geyser basin is a really dynamic area. It's one of the hottest areas of the park and it's also one area in the park where we see focused deformation, or swelling of the ground, where the ground actually uplifts and subsides," Hungerford says.
All of that might have created channels for fluids to move around underground. But researchers do not have detailed maps of what's going on beneath Steamboat.
"What is the subsurface architecture?" White wonders. "What is the volume of water that is available for every eruption?"
"People always ask, 'Well, why is steamboat such a tall geyser?' We can't answer that question," Manga adds.
Scientists do have temperature sensors deployed around the geyser. And there have been recent studies using arrays of seismic sensors. It appears that Steamboat's liquid is stored at depths of about 65 to 130 feet, Manga says.
"The deeper water is stored, the warmer it will be. That heat provides the energy that drives the eruption," Manga says.
"At other geysers, that storage seems to be more shallow," he explains. "And our hypothesis for the reason why Steamboat is such a huge geyser and so tall is that the water is stored deeper. The deeper the water is stored, the more energy it can have. And the more energy you have, the bigger the eruption can be."
Some of the first studies of geysers were done in the 1800s, by Robert Bunsen — the same guy who developed the Bunsen burner used in chemistry classes. Scientists have put video cameras in geysers and have built artificial geysers in the lab.
Still, it's not so easy to find funding to study something like geysers, and the list of unanswered questions goes on and on, Manga says.
He rattles off a list: "Why do geysers exist in the first place? What is it about the geometry that makes something become episodic? Why do eruptions end? Why don't they just continue? How do geysers respond to external forces? What controls how high a geyser eruption is?"
Millions of people travel to see geysers each year, and part of the draw may be their air of mystery. Steamboat has become a superstar, eclipsing even Old Faithful in terms of public attention and the effort people make to try to catch an eruption.
"There are people that camp on the sidewalks, spend all of their days, all of their time off, sitting next to Steamboat," White says.
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