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."

Comments

Related to California Quake a few days ago?

[J-bob2]

I couldn't help but wonder if the two are related? Is Mt. St. Helens related to the the quake in California on Tuesday? They're in that same general fault line aren't they?

Can anyone who knows more about Earth Science help me out here?

You think Mt. St. Helens was big...

[RCulpepper]

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.

Re:Someone take pictures of the near area before

[Sam Treadwell]

I hiked there about 2 weeks ago, on Boundary Trail #1 and 207a, which runs along the base of the mountain and Spirit Lake. Got some great photos. Sometimes it is great living near a volcano. heh.

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

Lahars

[esoterus]

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.

Re:Portland Oregon threatened in last eruption

[mikerich]

However on the west side of the mountain, there was a nuclear power plant on the Columbia river about 50 miles (80 km) away. If the volcano had blown out through the west side of the mountain instead of the north side, there was the serious possiblility that the shock wave would have ruptured the reactor coolant tanks and damaged the control and safety systems. In a worst case, this could have led to the release of radioactive material into the last 50 miles of the Columbia river. The river would have been closed for shipping. Which means that the port of Portland would have been closed, stopping shipment of massive amounts of grain to Asia from the Pacific Northwest. It would have also caused the extinction of the fisheries, such as salmon and steelhead trout in the Columbia.

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.