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Mount St. Helens Alert Status Increased
DarkHand writes "Mount St. Helens has become even more unstable in the last few hours. The U.S. Geological Surveys Cascades Volcano Observatory has increased the volcanic alert around the volcano to level 2 and released a press release: 'Over night, seismic activity at Mount St. Helens has accelerated significantly, which increases our level of concern that current unrest could culminate in an eruption. We are increasing the alert level to the second of three levels [...]. Earthquakes are occurring at about four per minute. The largest events are approaching Magnitude 2.5 and they are becoming more frequent. All are still at shallow levels in and below the lava dome that grew in the crater between 1980 and 1986. This suggests that the ongoing intense earthquake activity has weakened the dome, increasing the likelihood of explosions or perhaps the extrusion of lava from the dome.' The most recent readings at the SEP seismograph stationed on the lava dome itself are totally saturated. The ground is now literally constantly rumbling."
I was there about ten years ago, with a college field trip. Being from the Midwest, I haddn't seen any real volcanos until then. I was looking forward to seeing the terrific devistation and other formations left by the 1980 eruptions.
While driving up the windy mountin road to get to the park, our van turned a bend, and suddenly I saw before me a swath of devistation so utterly complete that I knew only some tremendous force could have removed all the trees and other signs of life.
I asked the "vetrans" of the group if we had reached the blast zone already. They responded: "Nope, that's just a clearcut. The blast zone now has much more wildlife."
Ah well. I was just there to look at the rocks anyway.
Can anyone who knows more about Earth Science help me out here?
Google 'Yellowstone volcano.' In one of the two or three times I favored my intro to geology class with my presence, my professor explained that much of Yellowstone National Park is the caldera of a giant volcano, according to him the largest on earth, hence the geysers and sulfurous springs. If it were to erupt again -- fortunately it does so rarely, about once every 600k years -- it would cover most of the Western US in ash and if it did so without warning, would kill millions of people.
Always a godfather; never a god. -Gore Vidal
Here is a fairly large panoramic we took that day. You can see Johnston Ridge Observatory on the far right. The trail actually takes you across the ridges on the left and then drops you down in to the flats at the base of the mountain:
http://home.pacifier.com/~richmond/Helens.jpg
One of the more reassuring things about St Helens blowing is that it has already done so. It has a nice crater to keep things fairly contained and no glaciers. Mt Rainier is another story, however. It is also a volcano, has the most permanent glaciers on it of any mountain in the continental US and if it blows, the true danger is what happens to those glaciers at eruption. It's known as a lahar.
I read something similar to this once: To get an idea of a lahar, imagine a 30 ft wall of mud, boiling in temperature with the consistency of wet cement traveling at speeds up to 60 mph or so. If you go driving through the river valleys of Washington State (Carbon Rv, Puyallup Rv) that are fed by the Rainier glaciers, you'll see Lahar evacuation route signs everywhere. Not only that, but I believe recent evacuation simulations have been abysmal. Scary stuff.
Ahh, may have found the article that I read.
Not only does God definitely play dice, but He sometimes confuses us by throwing them where they can't be seen. -Hawking
I clearly remember 1980. It was pretty neat and scary. Although it happened on Sunday, so we didn't get that day off of school. I think school was closed for several days afterwards. Some tidbits that you may find boring or interesting...
Ash was so fine (there was several inches on the street) that it would ruin your engine. So everyone put women's pantyhose over their air cleaners to keep the dirt out. Also the local timber company bought out the auto parts stores of all the extra air cleaners to keep their trucks moving.
people kept emergency supplies in their car trunks for years after that. probably until 86 or 87
Also, their were some great slogans on bumper stickers and t-shirts that we'll revive if necessary.
"Mt St. Helen's lost her ash in 1980, I saved mine."
Plus the song about harry truman was popular.
wow, amazing what you can remember...
Although both Mt Rainier, Mt St Helens, and all the other dormant and volcanoes in Washington and Oregon are due to the same subduction zone; an eruption at Mt St Helens will not influence Rainier in any way.
The USGS is currently predicting a high likelihood of Rainier experiencing a small eruption in the next 50 years. This will melt Rainier's icecap and produce lahar flows (heavy, fast mud flows - these will take out bridges and buildings). The outskirts of Seattle are built on the deposits of old lahars from Rainier...
Early this year, a warning system (a bit like the tsunami system in the Pacific) has been put in place between Rainier and Seattle. This should give warning of lahars as they start. This could give enough warning to get people out of valley bottoms, etc - but how much of the populace knows what a lahar is and what the danger is???
Incidentally, a couple of days ago, I plotted the ongoing Mt St Helens earthquake swarm on some earthquake hazard maps and put the results here.
Richard (yes I was a seismologist 10 years ago)A friend sent me this link to the Mount St. Helens Volcano Cam, updated every 5 minutes from the Johnston Ridge Observatory.
I was going to college in Moscow, Idaho when it blew, and believe me, it was impressive, even that far away from the eruption.
Throughout the day a tolkeinesque black cloud grew larger and larger on the western horizon, until it streched all of the way north to south. As it came over it became darker than night, the sky was just black. Then is started to "snow" volcanic ash. Instead of coming down in flakes, it came down as a fine powder, but looking out the window, it looked like snow against the street lights. This was about 3:00 in the afternoon.
It didn't get light again before nightfall. The next morning, it was as if it had snowed, except it was very finely powdered ash, and it didn't go away like snow, it just compacted and then blew around as dust when the wind blew.
It was a very memorable experience, more impressive even than a total solar eclipse (but that's another story)...
A house divided against itself cannot stand.
It's unlikely that even the most massive eruption from Mt. St. Helens could have threatened the plant. The incredible first lateral blast only travelled 25km and IIRC the pyroclastic flows only extended about 20km. Ashfall would not have been a problem for the plant, and the quakes associated with vulcanism are (Hollywood aside) fairly small.
In the event, they had a pretty good idea that Mount St. Helens was going to erupt through its side. The area that bulged was called Goat's Roack and was actually the result of an earlier eruption through the side of the cone.
What no one had predicted was that the whole side of the mountain would slide off. Instantly a huge section of the magma below the mountain depressurised - like a champagne cork blowing off. And that did the damage.
What we have now is young magma pushing up under the mountain. We'll probably see a series of small eruptions as the dome is built, extended and then blown apart. We could have centuries of this sort of activity ahead of us.
The eruption was too bad because Mt. St. Helens was a perfect cone before the eruption. It looked like Mt. Fuji in Japan. Now it looks like a million-seat football stadium: a big hole with a circular ridge around half of it.
You're not thinking long-term - the cone of Mt. St. Helens was only a few tens of thousands of years old, it will rebuild itself in the next few millennia. In the meantime, sit back and watch the mountain heal itself.
Best wishes,
Mike.