Let’s say I put on a heat-resistant suit, persuaded a reckless scientist to miniaturize me (à la “Honey, I Shrunk the Kids”) and rappelled into the Old Faithful geyser. After going down 20 feet into the geyser’s vent — which is about three feet wide — I’d find myself passing through a much more narrow four-inch slot that eventually gives way to an alcove. There, I’d find water cascading through rocks — an underground waterfall of sorts. This rain and snowmelt passes through faults up to 3.1 miles deep in the plateau. Once it’s heated by the partly molten magma underlying Yellowstone, it boils its way back up through the cracks. 

Like commuters jostling to hop off a bus at rush hour, bubbles start crowding into bagpipe-like tubes, forcing water up and out of the geyser. The pressure drops for a second. Then, suddenly, there’s a loud POP! The boiling water is now steam, ballooning to 1,500 times its original size before detonating upward in a 244-degree Fahrenheit fiery jetstream. Traveling at supersonic speeds, I would catapult back out of the furnace at heights of up to 184 feet. Fun, if it wasn’t so deadly.

About 90 minutes later, the process repeats itself, and Old Faithful explodes again. This is roughly the same interval that has bridged its eruptions for more than 20 years. It’s kind of like the Jerry Seinfeld of geysers — a charismatic creature that predictably delivers (watery) punchlines. It can be taken for granted that water bursting through the earth is, in itself, a miracle of nature. To erupt, geysers need vast amounts of heat, a large supply of water, and, crucially, the right cavities and fractures underground to channel pressurized liquid to the surface. 

Yellowstone National Park is home to Norris Basin geyser, above, and half of the 1,000 geysers on the planet.

This restrictive formula explains why there are only about 1,000 known geysers in the world, and why half of them can be found in Yellowstone National Park: The plateau harbors all of these elements in abundant quantities. This, in turn, explains why about four million visitors take to the park’s planked walkways to gawk and awe at them every year. On a frigid day this April, I’m one of them.  

But as I wait to watch Old Faithful erupt for the first time, grim predictions in a research letter published two years ago in Geophysical Research Letters (a peer-reviewed journal) cross my mind. “Climate models project increasingly severe droughts by the mid-21st century, suggesting that geyser eruptions could become less frequent or completely cease,” wrote lead study author Shaul Hurwitz. The big hand of climate change is turning the spigot off to Yellowstone.

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I’ve been traipsing about the park with Mara Reed, a cheerful doctoral student who studies geysers at the University of California, Berkeley. She’s wearing a bright bumblebee-yellow jacket, black rain pants and a beanie that mimics the color gradients in some of the park’s hot springs — green, purple, blue, yellow, orange and red. A self-described “hydrothermal zealot,” Reed, 26, navigates Yellowstone with a preternatural instinct. I somewhat expect her to wave at geothermal features as she describes them. “If you were to give this one a name, what would it be?” she asks as we plod through foot-deep snow past a hole in the ground. The tiny geyser gurgles up hot water and sounds like a thirsty dog lapping from a bowl. “I call it the slurper,” she says. 

Looking at the almost bucolic landscape, framed by woodsy hills and mountains, it’s hard to fathom that we’re atop a massive volcano. Only from heights that aircraft can reach can one make out the contour of the caldera that covers a large swath of the park — the result of an epochal eruption dating back 630,000 years. About five miles under my waterproof boots are two huge chambers filled in part with molten rock. The energy released by magmatic fluids largely explains why thousands of small earthquakes — 2,773 recorded last year — are released in swarms across the crater, with most being imperceptible to visitors. These molten rocks supply the heat that boils the snowmelt and rainwater seeping through the soil. And this water, in turn, fuels the geysers, hot springs, fumaroles and mud pots that make Yellowstone, well, Yellowstone.

This complex machinery is what made Reed fall in love with the region. She’s stopped counting the number of times she’s journeyed to the Upper Geyser Basin. This area concentrates some 300 geysers over a stretch of land smaller than Central Park. As a college student, Reed spent two summers running around the basin to catch as many eruptions as she could (in between scooping ice cream cones for one of the concessionaires, that is). When Steamboat, the world’s tallest geyser, started erupting again in 2018 after a three-and-a-half-year hiatus, she drove all the way from Portland with a friend to witness the event. They sat in front of the geyser all day, then put their puffy coats on as day turned to night. After three small bursts, the geyser took off under the stars. “A lot of geysers are like puzzles,” she says. “It’s really fun for me to think about them and try to figure them out.” 

With fellow Berkeley student Anna Barth and University of Utah professor Jamie Farrell, Reed’s spent the past few days setting up a network of seismic instruments and a hydrophone to listen to bubbles forming and collapsing under the surface of two hot springs. Hot springs function more or less like tiny volcanoes, and geoscientists use them as proxies to safely study their larger congeners, says Michael Manga, a professor of earth and planetary science at U.C. Berkeley and Reed’s thesis adviser. 

Volcanologists aren’t the only ones doing fieldwork here. NASA scientists come to study the microbes that thrive in the geysers’ scalding, acidic water. They are the closest thing we have to monstrous geysers on Saturn and Neptune’s moons, and they can help us understand whether springs on these celestial bodies contain life. It “provides that unique geyser environment which you just can’t find elsewhere,” says Conor Nixon, a planetary scientist at NASA. 

But climate change is warping the pristine conditions of this gigantic open-air laboratory. Temperatures in Yellowstone are likely the warmest they’ve been for the last 800,000 years,  according to a climate assessment of the greater Yellowstone area published last summer — and they’re projected to rise by five degrees Fahrenheit by the end of the century. This means that what underpins the geysers’ existence could be compromised as the water supply contracts. Scientists know this because it’s happened before, to none other than Old Faithful. 

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Shaul Hurwitz and two other researchers step off the boardwalk, snaking around the backside of Old Faithful. The men, bundled in warm parkas, bright yellow vests (as to not be mistaken for intruders) and thick gloves, carefully trod around the cone. It was the winter of 2019. The scientists were scanning the mound for relics from the past — stumps of fossilized trees. 

Hurwitz, a hydrologist with the U.S. Geological Survey, had long known about the trees. In 1956, a park naturalist named George Marler found petrified wood on the mound. He’d been attempting to determine Old Faithful’s age and thought the fossil could provide a hint. Using (the recently invented) radiocarbon dating technique — which leverages the presence of carbon-14 in organic materials to date them — he estimated that the specimen was about 700 years old. The tree, he posited, had once stood in a forest covering parts of the mound. If true, this finding had far-reaching implications. The reason there are no plants immediately around geysers is that the alkaline water they spit out doesn’t allow them to grow. For trees to spring up on Old Faithful, the geyser would have had to fall dormant. 

Hurwitz heard through the grapevine that there may be not one, but several fossilized tree remnants on the mound. The rumors, it turned out, were well-founded. The men identified no fewer than 23 wood fossils around the geyser, ranging from fragments shorter than a paperclip to stems eight feet long. Some were loose; others solidly entombed in minerals deposited by thousands upon thousands of eruptions. They got samples from each and sent them to the Woods Hole Oceanographic Institution, a private lab in Massachusetts, for radiocarbon dating. 

Then-President Barack Obama his wife Michelle Obama, and their daughters Malia Obama and Sasha Obama tour the Old Faithful geyser in Yellowstone National Park, Wyoming, on Saturday, Aug. 15, 2009. | Alex Brandon, Associated Press

When he got the results back, Hurwitz was stunned. The trees had grown in a 100-year period stretching from approximately A.D. 1233 to 1362. This means that the geyser had stopped erupting long enough for trees to sprout and grow. If the mound was an ancient crime scene, then the petrified wood was the smoking gun. Hurwitz found the culprit soon after. An extreme drought had sucked the water out of the western U.S. between A.D. 800 and 1300, a period known as the “medieval warm period.” This coincided with the time trees towered over Old Faithful. “There was not enough water to feed the geyser, but there was still enough water to have trees grow,” Hurwitz says.  

These findings don’t bode well for the future of Old Faithful. The region is in the throes of the worst drought in 1,200 years, scientists say. In Yellowstone, warming weather has already translated into more rainfall in the winter and less snow melting into streams, according to the Greater Yellowstone climate assessment. “Snow is the big supply of water to this region,” says Cathy Whitlock, a professor emerita of earth sciences at Montana State University and a co-author of the report. “Losing snowpack is a big deal.” 

That’s not to say all water will suddenly vanish from the park’s inner circuits. Geyser water comes in part from ancient reservoirs replenished over hundreds and possibly thousands of years. But if there’s less water trickling into the system, the overall pressure drops, which means fewer eruptions, Hurwitz says. For this reason, he expects that the interval between Old Faithful’s eruptions will lengthen. 

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More staggered eruptions could have wide repercussions on the park, Hurwitz says. If visitors find themselves having to wait longer to see Old Faithful — already one of the most trafficked areas — it means even more congestion in the park. The National Park Service is already struggling to handle the number of visitors, which stood at nearly five million last year. In 2020 and 2021, it invested more than $100 million to improve transportation and reduce congestion. 

Ultimately, there might be nothing to see at all. Protracted dry periods “might just shut off” Old Faithful, Hurwitz says.

But that won’t mean that all geysers will react the same way to a dearth of water. “They all have their own personality,” says Manga, who co-authored the study on Old Faithful. “Some are going to thrive and become more active. Some are going to curl up in a little ball and hide in the corner and go dormant.”

Tourists photograph Old Faithful erupting on schedule late in the afternoon in Yellowstone National Park, Wyoming, on May 21, 2011. | Julie Jacobson, Associated Press
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Another possibility is that as the number of eruptions starts to falter, the tubes through which water flows become clogged with minerals, blocking liquid. Large quantities of water stuck underground without pathways to the surface might have some effect on seismic activity, according to Manga. But, ultimately, “we don’t know the answer to these questions” yet, he says.

Through her sunglasses, Reed checks her black digital watch. Old Faithful is due to erupt any minute now. We’re watching from an observation point overlooking the geyser’s mound, waiting for the first — public — eruption of the season. Even from this distance, we can make out the silhouettes of a couple dozen visitors standing by the geyser on the boardwalks, waiting. 

Then, it happens. Water starts coming out in bursts, as though Old Faithful is clearing its throat before the grand recital. “Come on Fifi,” Reed says. The sprays gradually take up more space, drawing elegant arabesques reminiscent of the fountains soaring in front of the Bellagio casino in Las Vegas. “It’s trying really hard,” Reed says. Then there’s a jetting sound as an ivory column of water rises more than a hundred feet into the air. It towers there for over a minute, a frail edifice threatening to collapse any second. And then, it does. As suddenly as it’s emerged, Old Faithful returns to the earth.  

This story appears in the June issue of Deseret MagazineLearn more about how to subscribe.

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