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YELLOWSTONE NATIONAL PARK: Mysteries below create new features .. only theories about why activity is increasing

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  • Ishgooda, Senior Staff
    Mysteries below create new features By MIKE STARK Gazette Wyoming Bureau
    Message 1 of 1 , Jun 1, 2003
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      Mysteries below create new features
      By MIKE STARK Gazette Wyoming Bureau

      YELLOWSTONE NATIONAL PARK - Park Ranger Brian Sudderman, while driving between Norris and Mammoth, first spotted it March 10 - thick ribbons of white steam pouring out of the wooded hillside just west of Nymph Lake.

      Five days later, geologists trudged through the snow for a closer look. Where there had been solid ground, they found a long line of open vents spewing steam into the winter sky.

      "They were roaring like a jet airplane," said Henry Heasler, Yellowstone's lead geologist.

      Yellowstone, home to about half of the world's geothermal features, had one more to add to the list.

      The unnamed feature near Nymph Lake, northwest of Norris Geyser Basin, is one of the newest pieces of evidence that unrest just below the earth's surface is, as it has for eons, changing the face of Yellowstone.

      Wearing protective gear, Heasler and his crew have visited the feature a few more times since then to measure it, take its temperature and try to understand why it appeared.

      So far, geologists know that there are 14 steam vents, called fumaroles, in a nearly straight line that stretches about 75 yards across the hill. The temperature in the main vent is 195 degrees Fahrenheit.

      Back in March, the trees around the vents still were green. Now some nearby are covered in fine, white debris, and others are brown and dead.

      "Basically, those are brown now because they have been steam-cooked," Heasler said, pointing out the haggard trees from a pullout in the road where the feature is visible.

      No one is sure yet what the white stuff coating the trees is.

      "It's some sort of dust that's being ejected by the steam vents," Heasler said. It's also unclear exactly what's being spit out of the vents. Most likely it's a mix of steam and carbon dioxide, but tests will be conducted to see what else it may be carrying.

      Heasler said it's possible that the steam contains sharp silica glass shards from lava rock beneath the ground.

      "If that thermal feature is disaggregating the lava creek tuff and it's forcing out the glass shards, then it's not something you want to be breathing," Heasler said.

      Until park officials know more about what the vents are sending into the air, they are asking visitors to keep away and view it only from the road.

      "Don't wander over to look at a thermal feature because you can damage it and it can damage you," Heasler warned.

      So, why the sudden split in the ground and a new thermal feature?

      That question has had geologists keen on Yellowstone chatting most of the spring.

      Chuck Wicks, a geophysicist with the U.S. Geological Survey in Menlo Park, Calif., theorizes that the new steam vents might be connected somehow to a large, emerging bulge in the earth just south of Norris and a series of smaller bulges between Norris and Mammoth.

      "I think it's just an introduction of hot fluids from deeper in the ground, maybe about 2 kilometers deep," he said. "Maybe this bending has provided some kind of pathway for these fluids. It doesn't look like an ongoing thing, maybe it's an episode or a pulse."

      Wicks emphasized that little is known for certain about what's happening in the area. He speculated that there may not be many more new features like the one at Nymph Lake because it appears that the force driving the smaller bulges may be losing steam, at least temporarily.

      There also is a pattern of faults between Norris and Mammoth that runs beneath the area that could be creating zones of weakness that reorganize the system beneath the surface and allow steam vents and other features to pop up, Wick said.

      Jake Lowenstern, the scientist-in-charge at the Yellowstone Volcano Observatory, agreed that faults in the area could be a cause of the Nymph Lake feature.

      "Maybe (it) has allowed some more hydrothermal fluid that was already here to move toward the surface," he said. The bottom line, Heasler said, is the feature needs to be studied more.

      "Until we get out there and measure it and see how it's evolving, we don't know," Heasler said. "We could say 'Oh, maybe there's magma here, maybe there's a carbon dioxide gas bubble under here, maybe there's additional hydrothermal fluid.' ... To hazard a guess right now would not even be as firm as a guess."

      For visitors, knowing the full story behind the Nymph Lake feature isn't necessary to enjoy it. From a pullout in the road at the edge of the lake, the feature is easy to spot and, between passing cars, it can be heard.

      "In the summer, with high temperatures and low humidity, it doesn't look very impressive, but if you're here early in the morning, generally you can see the whole line of steam vents," Heasler said. "It's quite vigorous."


      Scientists have only theories about why activity is increasing
      By MIKE STARK Gazette Wyoming Bureau

      YELLOWSTONE NATIONAL PARK - In the other-worldly landscape of Norris Geyser Basin, beauty, mystery and geology intersect. Its hot springs, brilliantly colored thermal pools, tempestuous geysers and spewing steam vents present the visitor with ever-changing wonders. Its inspirational show bespeaks secrets deep under the surface of the earth.

      And these days Norris, Yellowstone's hottest and most dynamic geyser basin, is talking plenty. Steamboat geyser - the largest in the world and one of the most unpredictable, with dormant periods as long as 50 years - has erupted four times in a year.

      Water in the basin is getting hotter and more is flowing through scoured channels into Tantalus Creek. The temperature inside Pork Chop geyser, which exploded in 1989, has risen by 8 degrees Celsius in recent months. Nearby, a swarm of about 100 earthquakes shook the area in 2000 and, more recently, a series of new steam vents cracked a wooded hillside near Nymph Lake.

      Something is afoot in the superheated chambers beneath Norris, but no one is sure exactly what.

      "This is an increasing activity trend," said Henry Heasler, the park's lead geologist, standing on the wooden boardwalk just downwind from the huffing of Steamboat geyser. "Part of the scientific question now is: How do we define that trend?"

      Norris sits on a series of faults that string toward Mammoth. The below-ground friction helped create some of the most recent eruptions in Yellowstone. There may be a direct connection with magma - molten rock miles below the surface - providing extra heat to the basin, said Jake Lowenstern, scientist-in-charge at the Yellowstone Volcano Observatory.

      "Certainly one explanation could be that either magma or thermal fluids are moving up in this region," Lowenstern said.

      Park geologists have been busy the past year or so placing new devices around Norris to measure water flow and temperature and record the exact times of eruptions. Heasler said raw data would be made available for scientific work on what's happening at the basin.

      But some of the most enticing clues about Norris are coming from space.

      Relatively new technology uses satellites to bounce radar off the earth to measure how much the ground is moving.

      Deployed to help measure the in-and-out "breathing" of the Yellowstone caldera - the giant collapsed volcano in the center of the park - the radar picked up another system at work.

      Just south of Norris basin is a bulge in the earth about 28 miles across and 7 miles deep that has pushed the ground up more than 5 inches since 1996, according to research by Chuck Wicks, a geophysicist with the U.S. Geological Survey in Menlo Park, Calif.

      That kind of movement of the earth in the Norris uplift, also documented by University of Utah geologist Bob Smith, is considered rapid in the perspective of geologic time.

      The discovery came as a shock to geologists who, until then, only knew of two "resurgent domes" in the caldera that slowly puffed up and down with the underground movement of hot water and magma.

      This third bulge, which sits partially inside and partially outside the caldera, prompted a series of new questions about what's happening beneath Yellowstone's surface.

      "It's fair to say the Norris uplift came as a surprise," said Dan Dzurisin, a Cascades Volcano Observatory scientist who has studied Yellowstone's geology for years. "But it's a continuation of the trend that for decades, each time we look at Yellowstone we discover something that surprises us."

      Is the swelling ground south of Norris related to recent activity like the return of Steamboat and hotter temperatures?

      There are theories, but no conclusive answers.

      "That's a tough one. It's tempting to say there must be a connection, but to go the next step and explain what that connection is could be pretty tough," Dzurisin said.

      He thinks that, at more than seven miles, the source of the uplift may be too deep to directly affect the hydrothermal system at Norris. It's possible, he said, that the bulge is opening underground fractures and allowing more heat to escape, which raises water temperature and stirs up activity near the surface.

      "But that's a long pipeline," he said.

      Wicks said it seems likely there's a connection between the inflating land and episodes at Norris, including recent Steamboat eruptions.

      The dome may be reconfiguring the underground system of heat, molten rock, water and channels to allow an extra boost of heat or hot water into the system, Wicks said.

      "This could be tweaking the shallow plumbing system somehow ... rearranging stuff so things can get up (to the surface) faster," he said.

      An earthquake in Alaska last fall touched off hundreds of earthquakes in Yellowstone in the following days, showing that the park's geology can be influenced even by faraway events, he says.

      "This whole area is sensitive to small movements in the system," Wicks said.

      The latest information on the Norris uplift shows that its expansion slowed in 2001 and 2002.

      Geologists theorize that the bulge eventually will subside, as did the other two domes in the park.

      While scientists try to understand the connection with Norris, they'll also try to figure out whether the newly discovered dome, which geologists say had probably been there for a long time before it was found, is linked to the other two domes, Sour Creek and Mallard Lake.

      Smith, from the University of Utah, pioneered work in Yellowstone showing that the caldera continually "huffs and puffs."

      Portions of the caldera rose more than 3 feet between 1923 and 1984 and then dropped nearly 8 inches from 1985 to 1995, according to Smith's research. Measurements in 1995 and 1996 showed that the caldera floor was rising again and then started to fall in 1997.

      The rising is probably caused by magma rising toward the surface but never quite breaking through, Smith theorized.

      Dzurisin says there's some anecdotal evidence that could link movement of the two domes to the Norris uplift, but it's tenuous.

      "As we watch these three things more closely, we'll see how they interact, if one goes up and the other goes down," he said. "We'll just have to see."

      Even if a connection between the domes is established, questions about new activity at Norris may not be answered.

      Geologists are still trying to understand the specific links between the deep churning magma beneath the park and spurting of geysers, steam vents (called fumaroles) and hot springs.

      Heasler, the park geologist, says all possible explanations of events at Norris are being considered.

      "You can go from two extremes: the climate and the atmosphere to the magma chamber ... and everything in between," Healser said.

      Either way, he said, it's an exciting time to be watching Norris.

      "With so much of this, we just don't know," Heasler said. "But that doesn't mean it can't be discovered."

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