Mt. St. Helens' Grumbling May Presage Eruption

stand writes "The Seattle Times is reporting (press release here) that scientists believe that there is a 'significant chance of a small eruption of Mt. St. Helens in the days or weeks ahead.' There have been a series of earthquakes at the site in the last few days. I think it's about time Washington state took over the natural disaster coverage from Florida, don't you?"

Comments

No reason to worry

[bar-agent]

From the article:

"Such an event could fling ash and rocks thousands of feet into the air but would not be expected to pose hazards beyond the volcano's crater and flanks."

Dupe

[complete loony]

Dupe Dupe Dupe Dupe ... (sung to the theme of Gold Gold Gold Gold ...)

Re:Just Washington?

[Anonymous Coward]

Probably not. It depends on the nature of the eruption and possibly (assuming a large enough eruption) which way the wind is blowing.

Most likely any eruption from St. Helens would be very small and unlikely to affect much outside the immediate crater. That is, only SW Washington would be affected. If, however, there were an ash eruption, the wind direction would be a critical factor in determining areas affected. The wind usually blows E to W, so it's unlikely that Northern Oregon would be much affected, although NE Oregon might see a little bit of ash. It would take a pretty sizeable volume of ash to make it all the way to Oregon.

In the event that a reasonable amount of ash-rich runoff made it in to the river systems, then Northern Oregon might be affected to the degree that the ash would affect water quality, ecology, or navigation in the Columbia River.

It is, however, unlikely that any significant volume of ash would be produced, since that would require a significant amount of magma making its way to the surface, which we'd probably notice pretty readily. At this point we know there's something going on down there, but not enough is happening to think any significant volume of magma is moving (or to even assume any magma is moving at all -- it could just be water).

So in summary: if anything happens Washington will be affected, but a pretty significant event would be required to affect Oregon. The probabilities are, however, that neither state will be materially affected.

Re:Controlled eruption?

[Anonymous Coward]

Humans have only ever induced a single volcanic eruption. If I recall correctly, it was at a steam well in Iceland where the well tube became a conduit that allowed a very tiny amount of tephra to erupt. It damaged part of the pipe.

To induce an eruption you would need to provide a path to the surface from an a pressurized magma body, and that path would have to be sufficiently robust to not get quickly plugged, or you would need remove enough pressure confining the magma that it could expand in spite of any remaining overburden. I'm not, however, a volcanologist so I don't know in a quantitative sense what kind of path to the magma you'd need to allow it to move or expand rapidly enough through the passage to maintain an eruption or not get plugged. Precisely what you'd need to do would certainly depend on the characteristics of the magma: dissolved volatile content, pressure, temperature, polymerization, and density among others. Again, I'm not a volcanologist.

There might be problems doing a lot things that would trigger an eruption.

For example, you might decide to drill a large diameter hole to the magma chamber, but doing so successfully would also destroy your drilling apparatus, never mind that if a magma body could be triggered, it would either probably be too deep to drill to in any reasonable length of time, or if you could drill to it fairly quickly you might be better off to just wait for it to erupt by itself (again, ignoring the problems of you erupting with it). Scientists are, in fact, drilling on various volcanoes around the world. Not to try to initiate an eruption (they've concluded there's very little risk of that occurring), but to understand better the internal structure of a volcano, cooling history, etc. Offhand I can think of drilling projects on Unzen (Japan) and Kilauea (Hawaii), but there are probably others.

You might take a different approach: if you could create a large enough earthquake you might, under some exceptionally optimistic scenarious, be able trigger an eruption: In the 1980 eruption the immediate trigger was a magnitude 5.1 earthquake below the mountain that triggered the catastrophic collapse of the north face. This removed a large mass of overlying material that was confining the shallow magma chamber, and seconds after sliding away that magma took the opportunity to blast forcefully out the gaping hole that had conveniently been opened for it. Elsewhere volcanism is often linked to structural controls that allow magma to dribble through to the surface, but a fault line that provides a preexisting zone of weakness or geologic control on the general likelihood of volcanism is very different from a fault or earthquake being directly responsible for a particular eruption. If you were trying to cause an eruption you probably couldn't count on a major throughgoing fault, never mind that it would be extremely difficult to cause a magnitude 5+ earthquake on demand. Even if you did manage to find some way to cause a huge earthquake, it's very unlikely that it could open a fissure that would depressurize a magma chamber. (Actually, depressurization might not be necessary -- it might be enough to nucleate a lot of bubbles if the the chamber were already in a critical state, but I don't know how reasonable such an approach would be. I'm pretty sure that at the least it would require a volcano that was just about ready to blow anyway for something like an earthquake to be a catastrophic nucleation trigger. Did I mention I'm not a volcanologist?)

But hell, if you can create a giant earthquake, why fiddle with trying to cause an eruption too?

So maybe another approach is called for. Consider reducing the confining pressure on the magma. You might be able to blast off the overburden, but if you have the explosive devices needed to remove a thousand or so vertical feet of rock, why waste time using them on a volcano? Instead of explosives, perhaps you could cause a large steam explosion by injecting large volumes of water in the fractured rock