Rich:
Here is another article I found on Yellowstone. You will find a lot of nay-saying in this article. Some of these are the same people that said Mt. St Helens, in Washington state would never explode. However Mt. St. Helens did explode. Mt St. Helens was a cindercone volcano, not a Caldera, such as Yellowston Park is.
Bill
A couple of years ago, the BBC published a report about a possible impending megaeruption; but there's some controversy about the threat now:
http://volcanoes.usgs.gov/yvo/faqs4.html#13
When will Yellowstone erupt again?
We do not know. Future volcanic eruptions could occur within or near Yellowstone National Park for the simple reason that the area has a long volcanic history and because there is hot and molten rock, or magma, beneath the caldera now. Yellowstone is monitored for signs of volcanic activity by YVO scientists who detect earthquakes using seismographs and ground motion using GPS (Global Positioning System). YVO has not detected signs of activity that suggest an eruption is imminent.
The crust of North America continuously moves southwest over the Yellowstone hotspot as the Earth's crust stretches above it, promoting the ascent of heat and molten rock. These processes produce basaltic magmas within the Earth's mantle, which rise into the overlying crust and continue to heat the rocks beneath Yellowstone, maintaining and possibly adding to the rhyolite magma in the crust above.
Yellowstone's 2-million-year history of volcanism, the copious amount of heat that still flows from the ground, the frequent earthquakes, and the repeated uplift and subsidence of the caldera floor also testify to the continuity of magmatic processes beneath Yellowstone and point to the possibility of future volcanism and earthquake activity.
What type of eruption will occur if Yellowstone erupts again?
Yellowstone's volcanic and hydrothermal history suggests the potential for various kinds of eruptions in the future. The likelihood of a certain type of eruption occurring in the future can be judged by how often eruptions have occurred in the past.
The most likely type of eruption would not be volcanic but, rather, hydrothermal. This type of small, but still explosive eruption can occur from shallow reservoirs of steam or hot water rather than molten rock. These reservoirs are the sources of Yellowstone's famous geysers, hot springs, and fumaroles. Such explosions could blast out shallow craters more than a kilometer wide; as has occurred in the northern Yellowstone Lake Basin, including Mary Bay and nearby Turbid Lake and Indian Pond, and in western Yellowstone National Park north of Old Faithful. Each of these craters was produced by steam blasts within the past few thousand years.
The most likely type of volcanic eruption at Yellowstone would produce lava flows of either rhyolite or basalt; rhyolitic lava eruptions could also include explosive phases that might produce significant volumes of volcanic ash and pumice. Such eruptions could range in size from smaller than the 1980 eruption of Mt. St. Helens through much larger than the 1991 Mount Pinatubo eruption.
The least likely but worst-case volcanic eruption at Yellowstone would be another explosive caldera-forming eruption such as those that occurred 2.1 million, 1.3 million, and 640,000 years ago. However, the probability of such an eruption in any given century or millennium is exceedingly low -- much lower than the smaller eruptions mentioned above.
Is it true that the next eruption of Yellowstone is overdue?
The fact that two eruptive intervals (2.1 million to 1.3 million and 1.3 million to 640,000 years ago) are of similar length does not mean that the next eruption will necessarily occur after another similar interval. The physical mechanisms may have changed with time. Furthermore, any inferences based on these two intervals would take into account too few data to be statistically meaningful. To say that an eruption that might happen in ten's or hundred's of thousand's of years is "overdue" would be a gross overstatement. On the other hand we cannot discount the possibility of such an event occurring some time in the future, given Yellowstone's volcanic history and the continued presence of magma beneath the Yellowstone caldera.
and ...
http://www.talkabouttravelling.com/...ages/58523.html
Is Yellowstone Set to Blow?
by "Tom Beno" <
[email protected][EMAIL PROTECTED] > Oct 29, 2003 at 05:04 PM
Is Yellowstone set to blow?
Online observers and scientists see same clues, different future for park.
By Rebecca Huntington in the Jackson Hole Guide
For doomsayers and outside observers, signs are abundant the monster volcano beneath Yellowstone National Park is stirring and a catastrophic eruption could be imminent.
Scientists agree Yellowstone is changing; it is a living, breathing
caldera volcano. But scientists counter that those fluctuations are minor compared to the activity that would be expected as a precursor to a major eruption.
One Web site bluntly outlines the debate: "Yellowstone supervolcano getting ready to blow its cork ... Is this hype or do the facts support such a prediction?"
Scientists monitoring the volcano say it's hype. Web site publishers following the Yellowstone saga disagree. What is agreed upon is Yellowstone has had a violent past and much of what makes it tick still remains a mystery.
But, no matter how stark the differences of opinion, the world's first national park holds the power to superheat the public imagination and send up plumes of predictions by modern-day Nostradamuses, conspiracy theorists, science buffs, star gazers and geyser gapers, among others.
"Yellowstone is a big limelight regardless," said Bob Smith, University of Utah geology professor and coordinating scientist for the Yellowstone Volcano Observatory.
Interest over Yellowstone awakened this summer when the National Park Service temporarily closed trails at Norris Geyser Basin because of geothermal changes. Trails heated to 200 degrees Fahrenheit. Also, a new mud pot ,splattering boiling-hot acidic mud formed near a trail.
A month later, a report of a bulge discovered on the floor of Yellowstone Lake, further fueled speculation of an impending explosion.
One Web site, exodus2006.com, published dire accounts from readers.
One posting stated: "There is a large dead zone of animals and vegetation. Immediately outside this dead zone, vegetation has stopped growing and animals are migrating out of the area. New geysers and mud pots are springing up daily. You can physically see the ground bulging up, not only at Yellowstone Lake, but in several places in the park."
The Web site also reports strong smells of sulphur, fish floating dead on streams and fishing closures as a result. Scientists say such claims are, exaggerated or misconstrued regarding phenomena not uncommon in Yellowstone. For example, new hot springs and thermal features have formed this year and killed vegetation in the process, Smith said.
But this has happened before. In 1978, vegetation and trees died in a half-mile wide area near the Norris basin after a swarm of earthquakes and changes in thermal features, said Smith, who has been studying Yellowstone's geology for 40 years.
"This is part of the natural evolution and the changes that occur when you have a dynamic system," Smith said. "Things that are normal at Yellowstone wouldn't be normal at other places.
That's why it's Yellowstone. It's a place of change."
As for reports of fleeing animals and people, Yellowstone spokeswoman Cheryl Matthews said Tuesday that the only exodus is seasonal employees, who typically leave after the busy summer season. Likewise, some animals typically migrate out of the park in the fall to winter ranges.
Also, Matthews said park officials have documented dead fish floating in rivers and lakes this summer. The Park Service did close rivers that became too warm this summer, she said. Those rivers heated up due to a combination of hot summer air temperatures and thermal run-off, she said.
Exodus2006.com publisher Andy McCracken acknowledged some postings on his site "might not be accurate" because he does not verify claims, e-mailed to him. A religious Rastafarian, McCracken lives in Hemel Hempstead near London and started the Web site in 1999. His site focuses on natural disasters of Biblical proportions with predictions of when they will occur and tips for survival.
McCracken initially became interested in Yellowstone's volcano after seeing the BBC's "Supervolcanoes" documentary. The documentary describes caldera-forming volcanoes. Supervolcanoes are not the traditional columns of magma, which form cone-shaped mountains. Instead a chamber of magma becomes a boiling reservoir in the Earth's crust that builds up colossal pressure before erupting.
Yellowstone's last caldera-forming eruption was 640,000 years ago. The impact of such an eruption today could destroy huge portions of the U.S., spew devestating amounts of ash, cause economic collapse, kill thousands and trigger climate change, the documentary warns.
Many of McCracken's concerns stem from information provided by scientists interviewed in the documentary, including Smith. Trail closures at Norris this summer stimulated more interest in the Yellowstone supervolcano, McCracken said via e-mail.
Smith called the BBC documentary well-done but said producers tended to paint the worst-case scenario instead of including more conservative views. For example, Smith has concluded "maybe supervolcanism has stopped at Yellowstone."
In contrast, the BBC documentary concludes with scientist Michael Rampino saying: "It's really not a question of if it'll go off, it's a question of when. Because sooner or later one of these large super eruptions will happen."
Recent online accounts of changes at Yellowstone have resurrected Rampino's comments on the documentary as further evidence of cause for concern.
Yellowstone Volcano Observatory Scientist-in-Charge Jake Lowenstern agrees a future eruption cannot be ruled out. There have been three very large eruptions at Yellowstone in the geologic past. Since that time there have been between 10 to 20 similar caldera-forming eruptions at other places on earth with the last one erupting 75,000 years ago.
"They occur. [But] they don't occur very often, and Yellowstone is a possible place for one to occur again," he said.
However, recent accounts are creating unnecessary anxiety based on little to no data, he said Monday.
"They have minimal data, and yet they're willing to leap to the assumption that the volcano is about to grow," Lowenstern said. "Our experience is we would have weeks to months of increasing activity prior to an eruption."
Likewise, Smith said: "I don't think we'd be surprised by an eruption."
Scientists don't dispute Yellowstone is experiencing changes. Lowenstern noted the creation of new hot springs near Nymph Lake and the Ragged Hills. Smith pointed to the fifth eruption of Steamboat Geyser in two and a half years after a decade of near silence.
But those changes do not signal an imminent eruption, they said.
Lowenstern and Smith agree that they would be documenting more swarms of earthquakes and ground deformation if Yellowstone were ready to blow.
A magnitude 4.4 earthquake Aug. 21 and a magnitude 3.3 aftershock Sept. 10 were recorded in the southern end of Yellowstone. But those quakes fit the normal pattern, Smith said, and overall, earthquake rates in the park are down.
"There's a group of people that like to amplify and sensationalize things that don't deserve it because there's no real evidence for it," Smith said. "I think we're trying to be careful and prudent to do our science."
Reports of ground deformation also have spurred speculation. U.S. Geological Survey researcher Lisa Morgan, who has been surveying the bottom of Yellowstone Lake, identified a bulge about 2,000 feet long and about 100 feet above the lake floor.
Although Morgan reported the finding this year, the bulge may not be new, Lowenstern said.
"We have better maps so we're able to see things that we couldn't see before," he said. "That doesn't mean that we're better able to understand what hazard they pose."
Researchers will monitor the bulge to see if it is growing, he said.
Smith has documented ground deformation of almost the entire caldera, which is about 3,000 square kilometers, using survey data dating back to 1923. By 1985, much of the caldera had swelled almost a meter, Smith said.
By the 1970s, the swelling had tilted Yellowstone Lake like a giant
bathtub, causing water to flood to the south end of the lake, drowning trees. (The bulge mapped by Morgan, in contrast, is but a pimple on the caldera and not a factor in flooding, according to scientists.)
"Everyone got all excited that that was a precursor to a big eruption," Smith said of the caldera swelling.
But then the ground began to deflate with hydrothermal fluids leaking out, he said. "Not only is it a living caldera, but it's a breathing caldera," Smith said.
The ground began to inflate again in 1995. But this time, only the
northwest side of the caldera is rising while the northeast and southeast portions are stable or dropping, he said.
Yellowstone is signaling the story is more complicated than a simple rise and fall of the earth's crust, Smith said.
Park officials also have seen changes now underway in previous decades. The newly-active Steamboat Geyser, for example, erupted 23 times in 1982, Matthews said.
Meanwhile, as debate has heated up over the supervolcano, trails at Norris have cooled, prompting Yellowstone officials to reopen all but 1,000 feet of footpaths on Oct. 9.
Marshall Masters, who is based in the San Francisco Bay Area, sees changes in Yellowstone as a "harbinger of a broader global pattern,"
Unlike McCracken, Masters said he does not publish hearsay though he gets plenty of it. His sources are news media, NASA and other legitimate sources, he said.
Lowenstern disputes claims on Masters' Web site and some radio talk shows of increased volcanic activity and suppression of monitoring data because politicians don't want to scare tourists away from Yellowstone. "My legal responsibility is to provide warnings to the landholders and the public," Lowenstern said. "If there's anything that's happening, we'll let people know everything that we know."
