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Over four million people trek to Yellowstone National Park each year. No doubt, some of them have likely experienced the feeling of the ground beneath them breathing; literally moving up and down. But as it turns out, those visitors really aren’t hallucinating pulsations. The park floor does, in fact, rise and fall, in the range of up to five inches. And scientists now understand why.

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The swath of Yellowstone that appears to breathe encompasses the Norris Geyser Basin, the park’s hottest thermal region. It’s long been the most dynamic of the area’s naturally heated pockets. Between 1996 and 2004, in fact, a particular 18-mile stretch around the basin rose almost five inches into the air.

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Slower movements later gave way to the Norris Geyser Basin’s full-on pulsations, which began in 2014. According to Live Science, the swelling ground started to feel like “a slow-motion Jack-in-the-box.” Imagine slowly cranking the arm of this classic toy and the figurine slowly creeping upward – that’s how it felt to trek over this geothermal expanse.

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Of course, Yellowstone and all of its incredible natural features have long been on scientists’ radar. A landmark 1979 study began to explain why the land there might shift. But a specific look at the Norris Geyser Basin – the results of which were published in 2020 – finally explained how the park’s specific situation led to pulsating ground.

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You’d be hard pressed to find a part of the Norris Geyser Basin that isn’t at the boiling point for its elevation, 199 degrees Fahrenheit. Indeed, it’s the hottest of the park’s thermal areas. And believe it or not, with a depth of 1,087 feet, researchers have recorded temperatures of up to 459 degrees.

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But heat isn’t the Norris Geyser Basin’s only noteworthy feature. It also stands as the oldest thermal area in Yellowstone. In fact, evidence indicates that it has been emanating warmth for 115,000 years, at the very minimum. And it just so happens the terrain is as dynamic as it is old and hot.

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Much of the Norris Geyser Basin’s activity comes from seismic shifts, but the ebb and flow of water can also disturb the geothermal area. Most of the H2O within the basin has some acidity to it. Therefore, its acid hot springs, including the world’s tallest, the Steamboat Geyser, prove a popular draw for park visitors.

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The Steamboat Geyser’s activity exemplifies just how temperamental the Norris Basin environment can be. Its biggest blasts send water flying into the air anywhere between 300 and 400 feet straight up. However, its extra-large eruptions don’t occur on any sort of schedule, nor do they last an equal amount of time.

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For instance, the Steamboat Geyser has had major blasts that occurred at an interval of every three days but, sometimes, it goes a half-century before a 300-foot eruption. The duration of these emissions can vary, too. Some subside after just 180 seconds, while others have raged on for 40 minutes at a time.

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From March 2018 through the time that the Norris Basin research emerged in 2020, the Steamboat Geyser had seemingly awakened. Its sporadic spouting became much more predictable, with explosive ejections occurring every week. And, in 2019, it set a record for the most eruptions in a single year with 48 – beating the record of 32 set the previous year.

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But the Norris Basin is more than just the Steamboat Geyser. It’s actually made up of two separate zones – the Back and Porcelain Basins. The former is heavily wooded, while the latter portion has proven inhabitable to trees. Instead, it has a slew of sounds, scents and colors for visitors to experience.

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Yellowstone guests can explore both sides of the Norris Geyser Basin, as each features trails and boardwalks to traverse. Of course, it requires careful crossing, since the mass majority of the water in the geothermal area simmers at 199 degrees. And that’s not just hot, that’s boiling at the park’s elevation.

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And yet, the geothermal water beneath guests’ feet hasn’t necessarily been the biggest concern for park goers. Not is it for the experts who have dedicated their lives to studying Yellowstone. That’s because a stretch of land in the Basin – one larger in size than Chicago – has risen and fallen over the years.

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The first shift occurred slowly, over an eight-year period from 1996 to 2004. During that time, an 18-mile area of the Norris Geyser Basin rose to stand 4.7 inches higher than it did before. Between 2005 and 2013, though, some of that growth shrank away – the specified area dropped 2.8 inches back down.

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Things picked up considerably in just a few months at the end of 2013 and into early 2014. At that time, the same swath of land launched upward at a rate of approximately 5.9 inches per year. Yellowstone was no stranger to ground movements by then, but experts had never before recorded such a large rate of uplift.

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Then, in March 2014, a 4.9-magnitude earthquake shook up the Norris Geyser Basin. It might seem that such a seismic event would encourage further movement in the geothermal area. The shudders, though, actually seemed to slow the rate of uplift. But the ground then fell into an entirely different pattern.

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At that point, the Norris Geyser Basin began to sink and rise gradually. According to Live Science, it mimicked the motion of “a slow-motion Jack-in-the-box” as it cranked back and forth. That movement lasted until the start of 2019, when the ground started to fall. And this time, its direction went downward only.

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In spite of this new downward trajectory, the Norris Geyser Basin never quite returned to its original position. As of April 2020, the active 18-mile stretch of land sits about five inches taller than it did in 2000. And, considering the range of shifts over the past quarter-century, it wouldn’t be wise to rule out future fluctuations.

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Through all of the basin’s logged movements, scientists have been unsure as to why it moves up and down in the way it does. But extensive research published in 2020 makes sense of the years of activity in this area. It builds upon evidence discovered in the late 1970s, which revealed the material that lay beneath much of Yellowstone.

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The 2020 study appeared in the Journal of Geophysical Research: Solid Earth. The team included study co-author and U.S. Geological Survey researcher Daniel Dzurisin, and was determined to find out the uplift’s cause. So, they used satellite and radar data to look beneath the Norris Geyser Basin to see precisely what was going on.

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Right away, the team could see that the Norris Geyser Basin’s activity wasn’t linked to the explosive start of Yellowstone’s history. Approximately 640,000 years ago, a supervolcano erupted, creating the massive caldera at the park’s heart. The current shifts beneath the basin however, did not point to the volcano regaining its power.

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But the geologists did rely on some old information. More than 40 years ago, researchers sought to find out more about what was beneath the one-of-a-kind Yellowstone terrain. They published their findings in 1979 in the Science journal, revealing a very mysterious magma system that flowed beneath the park.

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That’s not to say getting to the source of the uplift was an easy task. Even with the knowledge of Yellowstone’s magma system, it would be tough for the current research team to understand the Norris Geyser Basin’s pulses. According to National Geographic magazine’s Robin George Andrews, “In a hyperactive volcanic region like Yellowstone, the exact causes of any specific movement are difficult to pin down.”

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However, Dzurisin and the rest of the researchers may have found an explanation. As he told the magazine in March 2020, they realized that the Norris Geyser Basin’s shifts were probably nothing new. The geologist explained, “In all likelihood, Norris has been a center of [ground] deformation for a very long time.”

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Dzurisin’s statement – and research – was informed by decades-worth of GPS and satellite information. In addition, it explained why the ground seemed to breathe. The magma network, as discovered in the 1970s, forged its way into the area beneath the Norris Geyser Basin in the late 1990s, around the time that the area started to shift upward.

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Firstly, the data showed that magma had crept into the area beneath Norris Geyser Basin, approximately 10 miles beneath the surface. Its appearance caused the first of the noted shifts in the landscape. As a result, it slowly pushed the Chicago-sized area of land almost five inches upward between 1996 and 2001.

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But the magma didn’t just sit idly beneath the surface. While there, it released fluids trapped within its molten waves. These liquids bubbled up and traveled through the rocky crust above them. Not all of them, though, could escape through that way. Instead, they got stuck, building pressure beneath the Earth’s surface.

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Therefore, Dzurisin and his team realized, the rising pressure would push the ground upward. If the trapped liquids had the chance to escape through the rocks, though, the land would start to sink back toward its original position. In 2013, for example, the heated fluids got stuck underground, but that pocket popped with the 2014 earthquake.

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And, as it turns out, Steamboat isn’t the only Yellowstone-based geyser raising eyebrows. Old Faithful – noted for its reliable eruptions – has become more erratic over the years because of an earthquake six decades ago. Unlike the former, which remains within safe limits, Old Faithful’s wild activity could indicate a potential future volcanic eruption in the park. However, as with all of the park’s geysers, experts have a close eye on the situation.

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That pressure-release cycle continued more frequently after the 2014 earthquake, which caused the ground to sink. After that, the heated fluids moved through different fractures beneath the Norris Geyser Basin, eventually gathering closer to the surface. They continued traveling, pocketing and sometimes escaping, thus causing the up-and-down motion seen in recent years.

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Even with all of this information aligning with activity on the ground, the researchers knew their model was likely imperfect. That’s because the Norris Geyser Basin is just as prone to hydrothermal activity as it is magma-centric movement. All of which means that there could be different forces working to move the ground at any one time.

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Michael Poland didn’t take part in the new round of research, but he heads the U.S. Geological Survey’s Yellowstone Volcano Observatory. And he believes that the new information about magmatic movement shed light on what an incredible force they had in the park. The geologist said, “We’re only just beginning to understand just how dynamic [it] is.”

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There could, though, be other causes for the up-and-down, meaning the magma might not be the only element behind the Norris Geyser Basin’s changes. For instance, Yellowstone has seen heavy snowfall as of late. Perhaps it gathers in the landscape’s crevasses and escapes as the grounds shift. In other words, it might not just be fluids trapped in magma that are finally breaking free.

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As a result, Poland considers the research “a reasonable hypothesis, but it’s by no means certain.” Such findings, though, do give rise to other concerns surrounding the Norris Geyser Basin. For one thing, the research team wondered whether those magma-drawn fluids were just percolating beneath the park’s surface.

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Indeed, craters caused by hydrothermal explosions dot the landscape, both in Yellowstone and the wider region. These blasts occurred after hot water got trapped and lost its pressure. Then, after flash-boiling, it transformed into steam and made its way through the cracks in the rocks. Worse yet, the researchers have no way of predicting if and when such an episode could take place.

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Luckily, it is rare for a geothermal blast to be anything but minor. Dzurisin noted that the systems bubbling beneath the Norris Geyser Basin were incredibly intricate. So, the slightest shift – one that even the experts wouldn’t notice – could raise or lower the likelihood of an explosion. And such movements happen all the time.

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As such, predicting the potential of a geothermal blast is down to scientists’ speculation alone. That’s why officials decided not to close off Norris Geyser Basin to guests, as there would be no way to predict who was at risk and when. And, indeed, if they were even in danger at all.

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Interestingly, the research could also have a hand in explaining the Steamboat Geyser’s renewed activity. The experts realized that its number of eruptions had increased before – both in the 1960s and at the start of the 1980s. Data showed the raised level of ejections fell in line with the Norris Geyser Basin’s so-called breathing cycle.

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Still, even that pattern doesn’t completely explain the spout’s activity. Poland pointed out that the Echinus Geyser, which sits right next to the wildly active Steamboat, hadn’t seen an increase in eruptions. As such, the link between magma and the hot springs remains circumstantial. But as Dzurisin reiterated, “The timing does line up.”

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Researchers have only scratched the surface of their Norris Geyser Basin research. But they hope to study the liquids released from the magma in the future. And, even though much of the 2020 study results were only coincidental, Dzurisin pointed out the progress that the team had made. Such research would have proven “nearly impossible” two decades ago without the technology and techniques of today.

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