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| Volcano cooking up a mystery |
| 2006-05-19 |
| Credit where credit is due. I regularly trash the MSM's dismal reporting on science. However, I thought this was a very good, accessible but accurate piece on something that could be important. Scientists believe Mount St. Helens will erupt today, the 26th anniversary of the explosive eruption that produced the world's largest known landslide, killed 57 people and launched a new era in volcanology. "It's been erupting almost continuously since late 2004," said Tom Pierson, a U.S. Geological Survey researcher at the Cascades Volcano Observatory in Vancouver. So it's a good bet it will also erupt today, Pierson said. The real question that's "driving everyone nuts" in the volcano-watching research community, he said, is what's causing this period of eruption -- and if its peculiarities indicate the mountain is building pressure for another explosive event. Unlike the massive, catastrophic blast of 1980, the current eruption on St. Helens is slowly, steadily pushing up a relatively cool and solid column of lava rock, or magma. Right now, the spine, or "dome," that's building up in the crater is growing by about 4-5 feet a day. Although gravity forces it to constantly crumble back, it is now topping out at about 300 feet above the crater's glacial surface. The height of the new dome might not sound like much, Pierson said, but that's because it keeps breaking down to fill in the crater floor. He said this period of eruption has so far pushed out about 100 million cubic yards of magma -- enough rock to fill a football field 10.5 miles high -- and at this rate would rebuild the mountain in less than 100 years. And some think it could be building an increasingly bigger cork on a planet-size, pressurizing bottle of Mr. Fizzy Magma, leading toward another explosive eruption. So what's the big mystery about this eruption? "It's been very unusual in a number of respects," said Dan Dzurisin, one of the USGS' lead volcanologists at the Cascades Volcano Observatory. To begin with, Dzurisin said, there's very little gas emission. According to standard theory, he said, it is pressurized gas down deep in the hot magma that drives volcanic eruptions. But the ongoing eruption at Mount St. Helens is taking place without the expected amount of gas -- carbon dioxide, water vapor or hydrogen sulfide -- being released. "Mount Hood puts out more sulfur dioxide gas than Mount St. Helens," said Seth Moran, a USGS seismologist who gave public talks Wednesday at the Johnston Ridge Observatory overlooking the northwest-facing maw of the volcanic crater. "It's a weird one." The extruding lava rock also appears to be a lot cooler, by about 50 degrees Celsius, than has been observed in previous eruptions, Dzurisin said. This could indicate it is relatively cooler surface magma that is being driven to the top by another reservoir of highly pressurized magma much deeper down. Then there are the drumbeats. "We really wanted to figure out what those were all about," Dzurisin said. In September 2004, St. Helens announced its reawakening with some seismic rumbling -- a swarm of earthquakes. The volcano had been quiet since 1986 and the scientists had been forced to cut back on monitoring. They had to scramble to get more monitoring equipment up on the volcano. The only GPS instrument on the volcano at the time was at the Johnston Ridge Observatory. This satellite-positioning device gave the first inkling St. Helens was getting weird. Volcanoes moving into an eruptive phase typically inflate and bulge. At St. Helens, the GPS showed the mountain was actually deflating. The drumbeats began a little later, in October 2004. After the first swarm of episodic quakes, the volcano soon fell into a regular, rhythmic drumbeat of small quakes that mystified scientists and largely continue to this day. Another USGS scientist, Richard Iverson, suggested that the seismic drumbeats could be caused by an alternating process of dome building in which the molten rock gets stuck repeatedly as it rises. But when it rises, pressure is released. With less pressure beneath, the molten rock stops and solidifies within the volcano. Pressure builds up again, eventually forcing the rock up again. This type of movement, which the geologists call "stick-slip," is believed to create the regular pattern of quakes. Dzurisin said the model has been supported by field studies as well as monitoring data. "That was pretty exciting for us because it explained the drumbeats and also suggested a model for the eruption," he said. Iverson's explanation, Dzurisin said, also indicated that the solid rock of the lava dome was likely growing in both directions -- up and down. "We now know we've basically got a solid plug on top," he said. "Over time, the plug gets bigger and it takes more pressure to move it. The system is pressurizing." That's the kind of scenario that can lead to explosive eruptions, Dzurisin said. The scientists who have accumulated around Mount St. Helens since 1980 are widely regarded as world leaders in explosive volcanology. That's why John Pallister and three others from the USGS office in Vancouver were in Indonesia last week to assist with the threat of eruption from Mount Merapi. "We were sent there by the American Embassy (in Indonesia)," said Pallister. He's head of the USGS' Volcano Disaster Assistance Program -- sort of a rapid response team of scientists who are constantly bouncing around the world assisting with dangerous, explosive volcanoes. "St. Helens laid the framework for what we do," he said. Pallister said the Indonesian scientists already have a sophisticated monitoring system for listening to quakes and detecting ground surface changes (like bulging). But because of St. Helens' reawakening in 2004 -- when they got caught off-guard and the mountain quickly became too dangerous for anyone to go place monitoring equipment -- Pallister's team developed a new kind of monitoring device that can be slung into a crater or on an eruptive volcano by helicopter. They were at Merapi to consult with the local scientists and help if the situation became too unpredictable. The Cascade volcanoes are still pretty unpredictable themselves, noted Moran. St. Helens is perhaps the most well-studied volcano in the contiguous United States, he said, but it still can surprise and baffle the experts. If other dormant volcanoes such as Mount Rainier or Mount Baker started rumbling again, Moran said, we could have a hard time figuring what was going on in time. "We just don't have enough instruments out there on our volcanoes," he said. This week, Moran was at Rainier to talk with national park officials about placing some GPS units and more seismic stations up on the iconic peak. The danger on Rainier is not thought to be so much an explosive eruption as it is a massive lahar -- a volcanic mudflow. One Rainier lahar, some 5,600 years ago, produced a huge wall of mud and rock that reached Tacoma's Commencement Bay. Other prehistoric Rainier lahars have flooded the Duwamish Valley into what is now Kent. "It wouldn't necessarily take an eruption to trigger a lahar," said Pierson. A massive pre-eruption quake could destabilize the top of Rainier -- which is largely weak rock -- and cause a lahar. A quarter century after Mount St. Helens blew its top, we're still trying to figure out what's going on with the volcanoes in our back yard. |
| Posted by:phil_b |
| #7 did the same Deacon, under cloudy conditions about 5 years ago. It worked for me though as i was able to hike up into the restricted cone area due to the visabilty....and yes I have samples!! |
| Posted by: RD 2006-05-19 23:29 |
| #6 I climbed Mt St Helens back in 1990. Lots of gas and steam coming out. The trail was marked with posts as the trees were all gone and in cloudy conditions it was very easy to loose direction. |
| Posted by: Deacon Blues 2006-05-19 19:40 |
| #5 "We now know we've basically got a solid plug on top," he said. "Over time, the plug gets bigger and it takes more pressure to move it. The system is pressurizing." Think Grizzly Bear after 4 month winter nap. Not pretty. |
| Posted by: 6 2006-05-19 16:23 |
| #4 WX: what did St Helen's ever do to you to deserve THAT level of treatment?????? |
| Posted by: USN, ret. 2006-05-19 15:06 |
| #3 What about Chelsie, where the hell is she ? Surely nobody's doing that bowwow. Toss her in the caldron and run like hell. |
| Posted by: wxjames 2006-05-19 13:39 |
| #2 Not on the West Coast. |
| Posted by: Random Thoughts 2006-05-19 13:15 |
| #1 If only there were a virgin to sacrifice. |
| Posted by: Chuck Simmins 2006-05-19 13:09 |