- Associated Press - Saturday, September 26, 2015

YELLOWSTONE NATIONAL PARK, Wyo. (AP) - Last April, Yellowstone National Park officials noticed a new spring on Upper Terrace Drive near a popular parking lot that overlooks a white and gray travertine plateau sloping down to the traffic jam in Mammoth, Wyoming.

Hot water bubbled from the spring, or vent, as park geologists call them. Calcium carbonate deposits and microbial activity introduced by the water reshaped and recolored a small mound. A berm was built to keep the water off the pavement. In the summer, the park planned to build a more permanent solution.

It wasn’t strange. Springs at Mammoth are always changing. Vents start and stop at will. Visitors see different versions of the terraces every year. That’s nothing new, and no, a new spring doesn’t mean the Yellowstone volcano is going to erupt any time soon.

But this particular vent might be a little more complicated.

In mid-July, water was coming from the edge of the pavement, signaling the new spring was bigger than originally thought. Infrared pictures showed heat under the pavement. Park officials drilled two holes in the asphalt, and, sure enough, hot water bubbled out.

Those signals are what makes this vent more complex. All signs point to a thermal feature trapped under asphalt.

“The unusual thing about this is we have the road constraining this thermal evolution and the thermal evolution is impacting the road,” said Hank Heasler, one of the park’s two geologists.

The road - immensely popular with Yellowstone visitors - was closed for five days as officials tried to figure out just what was happening underground. Now, concrete barriers fence off the corner where the holes were drilled and long streaks on the parking lot mark where the water went before it was diverted.

None of this should arouse alarm. People and cars are allowed back there now. Each day they lean over the concrete barriers and marvel at the spring. Most know about Yellowstone’s thermal activity and they know it changes.

And whenever it does change, park managers respond. Boardwalks are moved, areas are closed, sometimes even roads are moved. This new spring is yet another natural wonder forcing their hand.

Unless it stops, which has happened before.

The vast underground system that provides the park’s natural crowd-pleasers does what it wants.

On a recent sunny day in Mammoth, Heasler and Cheryl Jaworowski - the park’s geologists - strolled the boardwalks and Upper Terrace Drive, talking about the importance of the park’s geothermal features. Without them, Heasler said, Yellowstone might not even be a national park.

“Say you come here in 1872 or 1870, and it takes you a couple of weeks to get here and you’ve got to come here on a horse,” Heasler said. “What’s going to impress you about this area?”

Animals? Well, those were likely more widespread then. And people used them for food more often than selfies.

The beauty? Sure, the area is gorgeous and remote, with the mountains and lakes and rivers.

But parts of Montana and the neighboring states had that too. So what’s so special about this Yellowstone place?

“All the thermal features. The hot springs, mud pots, geysers and steam bins,” Heasler said.

That’s also what brought these two geologists to the park.

Heasler used to teach at the University of Wyoming, Jaworowski at Laramie Community College. The pair have been at the park a little over a decade and they are working on a monitoring system gathering baseline data that will help them and others better understand how the system changes over time.

That includes both what happens above ground - Jaworoski’s specialty - and what happens underneath, Heasler’s realm.

They wear the park uniform and flat-billed straw hat with smiles and happily accept the certain level of celebrity that comes with it. Flurries of visitor questions, posing for photos now and then, kind of like wearing a Mickey Mouse costume at Disneyland.

But when not walking around in uniform, they are learning all they can about the geothermal features.

Heasler said more than 13,000 different features - including geysers, hot springs and mud pots - have been mapped in the park. About 26 square miles of visible thermal features exist in the park’s 9,000 square miles.

Some are like the terraces at Mammoth or Old Faithful - accessible and popular, the stuff postcards are made of. Others hide in the backcountry, cherished by hikers who know where to look.

But nobody sees what’s really driving the system. Underground, the thermal area is much larger than what’s visible, and it’s always moving.

“The thermal system is approaching park-wide,” Heasler said.

Because of the Yellowstone volcano, water and high temperatures occur at very shallow depths throughout the park. That’s what makes the thermal features possible, and what makes a fraction of the whole system come to the surface is location.

“That’s where the geology, the faults and fractures allow the heat and water to come to the surface and be expressed,” Jaworowski said.

Along those fault lines are where places like Old Faithful and Mammoth’s terraces form. That’s also where people want to go, so park designers made roads to take the hordes there and built boardwalks and trails taking them closer.

At Mammoth, the elaborate boardwalk system treads lightly on the white-gray slope formed by deposits from the calcium-carbonate rich water, known as travertine. Underneath that are caves and caverns, not solid rock.

But, as Heasler and Jaworowski know well, the system isn’t stagnant. Old travertine marks parts of the more average-looking hillsides, indicating where the springs used to be. Because of that, they don’t really know how new the “new” spring is.

Heasler said it’s close to another sporadically flowing vent, listed on some maps as “Baby Spring.” That one, he said, is known to have had water bubbling out in the 1930s and again in the 1960s, but has disappeared. This one could be an extension of it, but they aren’t sure.

That sort of change sometimes conflicts with the man-made infrastructure in the park. For example, hot water has engulfed sections of boardwalk at Mammoth from time to time, forcing park-hired carpenters to reroute.

“If you were here 10 years ago, you wouldn’t recognize the current boardwalk system,” Heasler said.

But now, what’s happening above the boardwalks, near the parking lot on the north side of Upper Terrace Drive, is different from just moving some lumber.


The original vent noticed in April is on a mound about 10 feet from the parking lot. The water moves downhill and takes a left turn, forced by the berm and one small log. About 15 gallons a minute rises from one of the holes drilled by the park officials, Heasler said, heading down a path sidelined by the parking lot’s edge and the mound’s slope. The two streams meet, and an orange track shows where it flows into a sinkhole.

But, as can be seen in the infrared picture and is hinted at by the man-made hole, that’s not the whole story.

“Right now, we don’t know what the thermal system wants to do because we have a cap of asphalt,” Heasler said.

The question park decision makers are faced with is balancing the needs of park visitors with the needs of the natural world.

There are a number of options. The road could be re-routed or become a pedestrian-only trail. The road could become totally off-limits, or they could do nothing.

Park superintendent Dan Wenk said that in cases when the park is asked to balance the needs of visitors and the natural world, they likely err more on the side of the natural world.

But, for this particular feature, Wenk said it’s way too early to know what will happen.

“We’re not exactly at that decision-making point yet,” he said. “What we’re going to do first is we have to make some kind of determination if this is a short-term issue or a long-term issue.”

What he means is they must consider the possibility that the vent could stop flowing any day. That has happened before, Wenk notes. He recalled a couple of different instances in the Mammoth area where a spring was near a road - not necessarily on the terraces - and by the time they were ready to make plans to manage it, the flow stopped.

“Maybe by the time we have that conversation, it’s a moot point,” Wenk said, though cautiously. He recognized the system could very easily go the other way too, like taking over the road.

He said his staff would consult with the geologists this fall and look for a way to move forward.

Either way, the two geologists are giddy about what they can learn from the new spring. Jaworowski is curious how it connects to nearby Cupid Spring, an outflow just across the road that she said is the most active spot she’s seen.

“I think it’s amazing and it makes me curious about the new hydrothermal activity we’re going to see across the road and what connection there might be,” she said.

That’s what it’s all about, she said. Learning, applying what she knows as she and Heasler spend their days in the nation’s first national park, keeping an eye on a massive thermal system only interested in itself.

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