Mt. St. Helens Crater Growth: What You Need to Know | CNN 2006 Article

[Astronuc]

Giant rock growing in Mount St. Helens' crater
http://edition.cnn.com/2006/US/05/05/mountsthelens.ap/index.html

A giant slap of rock is growing in the crater.

Hiking activities have been suspended and Mt. St. Helens has been closed to the public.

Keep an eye on it.

 

[J77]

Ohhh - cool

As long as no-one gets hurt, mind

 

[matthyaouw]

Thats pretty interesting. I wonder if it's being formed by new lava being pushed up, or faulting and compression as the dome subsides (I reckon the former is most likely). Either way that thing'll make a hell of a bang when it falls over!

 

[Astronuc]

Thats pretty interesting. I wonder if it's being formed by new lava being pushed up, or faulting and compression as the dome subsides (I reckon the former is most likely). Either way that thing'll make a hell of a bang when it falls over!

I am pretty sure that it's on top of the new dome, and thermal imaging has shown high temperatures indicating lava is close to the surface. This has been build for several months now.


USGS Page with Images of Mt. St. Helens.
http://vulcan.wr.usgs.gov/Volcanoes/MSH/Images/MSH04/framework.html

 

[scott1]

How could it happen again? Doesn't it take thoundsands of years for that kind of stuff to happen?

 

[hypatia]

How could it happen again? Doesn't it take thoundsands of years for that kind of stuff to happen?

Nope, as long as the magma is moveing, and pressure is building, there is a chance for another blow.

 

[turbo]

I still have a 35mm film can of ash from the last blow. Friends of ours moved out there to start a business. Not long after the blast, they let their black cat in through the patio door and the cat was grey, so they tried to shoo him back out. Then they noticed that pretty much everything outside was grey. It is a VERY dense film can of dust, and quite gritty. I'll bet lots of cars with cheap chain-store air filters started using oil pretty badly after that.

 

[scott1]

Nope, as long as the magma is moveing, and pressure is building, there is a chance for another blow.

But it won't be like the last one right?

 

[matthyaouw]

It probably isn't going to blow like in 1980. Since then it has extruded two lava domes, the first between 1980 & 1991, and the other one over the past couple of years. Its probably just another stage of the latest growth.

 

[Astronuc]

But it won't be like the last one right?

Mount St Helens sits atop the subduction zone where the Pacific plate is pushing the small Juan de Fuca Plate under the North American Plate. Any of volcanoes could develop like St. Helens, and St. Helens could be active for a while.

http://geology.er.usgs.gov/eastern/plates.html

 

[Integral]

Mount St Helens sits atop the subduction zone where the Pacific plate is pushing the small Juan de Fuca Plate under the North American Plate. Any of volcanoes could develop like St. Helens, and St. Helens could be active for a while.

http://geology.er.usgs.gov/eastern/plates.html

The Cascade Mountain Range of central Oregon consists of a series of volcanic peaks. Starting with Mt Hood in the north to Crater Lake in the south. Currently there is a growing bulge near the South Sister (the highest (~10,000ft) of the three sisters. Mt Hood has also shown some potential for new volcanic activity. One or both of these 2 mountains are visible (on a clear day) to about 90% of Oregon's population. The volcanic history of this Range of mountains is NOT over with. There will be more activity in the future, how much and when is not known.

Back in 1980 shortly after Mt St. Helens big eruption, I attended a seminar at the OSU Physics dept. Given by the volcanologist studying St. Helens. I asked then if they had any idea of how long it would take for St. Helens to rebuild itself. Of course the answer was, No.

It now appears that we may see a dome peaking above the rim of the crater within the next decade or so. How cool! It is my understanding that as long as the magma is moving the internal pressure will not built up, decreasing the chances of a repeat of the 1980 explosion. So the dome building activity is good news for the local ecosystems.

 

[J77]

But it won't be like the last one right?

I guess you mean that it won't blow from the side this time, right?

 

[Astronuc]

Well, the northside is lower than E, S or W, so any explosion would be toward the north primarily. But as Integral pointed out, the magma is much closer to the surface (thermal imaging shows the surface is hot) so most likely, there would not be a big explosion, unless there is a lot of gas in the magma chamber.

From October 2004 - http://www.theolympian.com/home/specialsections/MountStHelens/20041004/5349.shtml

There is not much mass left in the crater, which would cause a build up of energy.

 

[matthyaouw]

The pinnacle looks a bit like the http://volcano.und.edu/vwdocs/volc_images/img_mt_pelee2.html . Perhaps they're formed in the same way.

 

[Astronuc]

http://news.yahoo.com/s/ap/mount_st__helens;_ylt=AuXDcaz88YZwf4oFXpnF0beaK8MA;_ylu=X3oDMTA5bGVna3NhBHNlYwNzc3JlbA--

SEATTLE - The sheer rock fin emerging in Mount St. Helens' crater lost about a third of its northern face recently, but because lava keeps pushing to the surface, the height remained the same Thursday — around 330 feet.

A burst of seismic activity at the mountain Sunday night likely corresponded to the collapse. "Certainly a big piece fell off — something like 65,000 cubic yards," said geologist Dan Dzurisin at the Cascades Volcano Observatory in Vancouver, Wash., about 50 miles from the mountain and 150 miles south of Seattle.

Bad weather had iced over scientists' cameras on the rim of the volcano, so the rockfall wasn't recorded on film, he said.

Activity has picked up a little at MSH.