Giant Rock Growing in Mount St. Helens' Crater

An anonymous reader writes to mention a CNN article about the huge geological formation growing in Mount St. Helens' crater. From the article: "The fin-shaped mass is about 300 feet tall and growing 4 feet to 5 feet a day, said Dan Dzurisin, a geologist at the U.S. Geological Survey. The rock in the crater began growing last November, steadily moving west and pushing rock and other debris out of its way as it goes." Scientists think the mountain will eventually replace the lave dome blown out by the original 1980 eruption.

Re:Rebuilding

[anagama]

The eruption caused a massive debris avalanche, reducing its summit from 9,677 feet (2,950 m) to 8,364 feet (2,550 m) in elevation. Cite [wikipedia.org]. The mountain lost 1313 ft in its 1980 eruption. The article mentions the rock is rising 4-5 ft per day, and is 300 ft tall. It has 1003 ft to go, or about 250 days, assuming it continues at the same rate -- an unlikely assumption however because to replace the cone, it would need to not only rise to its former height, it would have to fill in the mile wide crater as well.

Re:Will the volcano have another major eruption?

[NMerriam]

An eight-year-old could have offered us as much insight.

Well, the difference is the eight year-old would be guessing.

The USGS stating that it's stable now but is capable of changing at any moment without warning is useful information, because it makes explicit that if something terrible is to happen they won't be able to see indicators 24-48 hours in advance and thus warn people away. If you want to get away, there is no precursor activity that will tell you when, so you just basically have to go and wait, potentially for a long time.

this is normal

[buldir]

This latest activity is normal for a volcano that typically erupts more silicic lava. The magma at depth is generally more viscous and after an eruption the momentum of the magma migration slows, but still continues to rise up through the vent due to residual pressure beneath the volcano. This type of thing occurs quite a bit at another volcano in Kamchatka, Russia, called Bezymianny. The dome builds up, then collapses, then rebuilds, etc. The USGS should no doubt be concerned with the growth of the dome at MSH, as a major collapse can easily cause a pyroclastic flow...nasty stuff. Questions remain, however, how much more magma is beneath the volcano and what is the rate of replenishment?

Old News

[trigggl]

This news is so old, the fin has already fallen over. The fin was reaching heights as high as part of the lowest parts of the crater rim, but has now fallen over. I didn't bother to read the article because I've been following this since the mountain became active again. It's errupting about a truckload of lava/rock a second. If memory serves, at the current rate, it will rebuild in something like 20 years.

I was in Eugene, Oregon when it blew in the 80's. I heard and felt a double blow all the way from there. All the Windows in the neighborhood were rattling. The news may keep saying it blew the top off, but that's wrong. Most of the mountain came down in a landslide. Once the landslide started, the pressure blew up and in the direction of the slide. It's the biggest landslide in recorded history. Watch out because when Rainier slides, it will be bigger. Scientists believe it's overdue. There are deposits from a previous slide in Seattle.

My mistake, this is a second fin

[trigggl]

I guess I should have RTFA.