Tuesday, 05 October 2004

Yes, people, we are still alive here - the media in some places is getting overly excited. Really, nothing has happened as far as any major events. There is no ash in Portland or pretty much anywhere else as of today. Please stay calm, move along, nothing to see here (well nothing catostrophic anyhow, but plenty of interesting stuff). If you want to keep in touch with updates on the volcano as I post them, I have created a new category for posts and a matching feed.


Mt. St. Helens this morning let off the largest of its steam and ash emissions so far since the new volcanic activity started. Portland's KATU News got some great spot video becasue they just happened to be in the air when it started. Interestingly, the seismic activity dropped off when this emission took place, and has remained mostly low-level since.

In the image below, taken from the University of Washington's webicorders of the St. Helens South Ridge seismographic station, the seismic activity drops off right after 9am, which is when the new cloud of ash and steam was emitted:

Activity has - as you can see - stayed at a lower level since, with a few larger quakes occurring among a lot of smaller ones.

Clicking on either image will open a new window with the full size image from the U of W webicorder site.

An interesting anomaly on the webicorder readout during the 11am Pacific Time hour shows what is either a strange (harmonic?) event or a simple error in the seismic recording. Anyone know or have any idea what the wandering lines represent?

At any rate, ash and steam from the mountain went thousands of feet in the air and for the first time ash amounts were detectable on weather radar. Small amounts of ash fell around small towns northeast of the mountain and on US Hwy 12, which resulted in reduced visibility, according to media reports.

The lava dome, which was formed between the big explosive event in 1980 and 1986, has raised more than 150 feet since the events started. Last week they were excited over a 2 centimeter lift - In the past 36 hours the dome has lifted more than 50 feet.

The forecast is for more events like the ones we have been seeing, with a likelihood of an eventual (sooner or later) explosive event. If magma (hot molten rock) reaching the surface (at which point it's called lava) is new magma from deep inside the earth, it will contain lots of compressed gasses, which will create an explosive type of event that throws rock and ash in the air. If it is old magma, perhaps left over in a relatively shallow cavern from the 1980 eruption, it might not contain as much gas, and as a result it may just flow out and help build a newer, bigger dome in the volcano's crater, a process that could - eventually - build the mountain back up again.

But the amount of ash being thrown about has grown with each steam eruption so far, and the levels of magmatic gasses have also grown, so I am betting on bigger event, rather than smaller. Nothing like 1980, mind you - but spectacular, I will bet.

Those Earth Science classes in high school and junior high did some good after all. See? Good teachers make all the difference in the world.



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