You think Florida's got troubles?

[revwardoc]

http://vulcan.wr.usgs.gov/Volcanoes/...t_updates.html

U.S. Geological Survey, Vancouver, Washington

University of Washington, Pacific Northwest Seismograph Network, Seattle, Washington Mount St. Helens Notice of Volcanic Unrest September 26, 2004 3:00 P.M., PDT Seismic activity at Mount St. Helens has changed significantly during the past 24 hours and the changes make us believe that there is an increased likelihood of a hazardous event, which warrants release of this Notice of Volcanic Unrest. The swarm of very small, shallow earthquakes (less than Magnitude 1) that began on the morning of 23 September peaked about mid-day on 24 September and slowly declined through yesterday morning. However, since then the character of the swarm has changed to include more than ten larger earthquakes (Magnitude 2-2.8), the most in a 24-hr period since the eruption of October 1986. In addition, some of the earthquakes are of a type that suggests the involvement of pressurized fluids (water and steam) or perhaps magma. The events are still occurring at shallow depths (less than one mile) below the lava dome that formed in the crater between 1980 and 1986.

The cause and outcome of the earthquake swarm are uncertain at this time. Several causes are possible, but most point toward an increased probability of explosions from the lava dome if the level of current unrest continues or escalates. During such explosions the dome and crater floor are at greatest risk from ballistic projectiles, but the rim of the crater and flanks of the volcano could also be at risk. Explosions would also be expected to produce ash clouds that drift downwind at altitudes up to several thousand feet above the crater rim. Landslides and debris flows from the crater that are large enough to reach the Pumice Plain are also possible. Such events occurred at Mount St. Helens between 1989 and 1991.

We continue to monitor the situation closely and will issue additional updates as warranted, whether activity escalates or returns to background levels. Daily updates of earthquake data and other information can be found on the WORLD WIDE WEB at URL: http://vulcan.wr.usgs.gov/Volcanoes/...t_updates.html and http://www.pnsn.org/HELENS/welcome.html

UPDATE: 09/25/2004 9:30 AM PDT Volcanoes in the Cascade Range are all at normal levels of background seismicity, but Mount St. Helens is experiencing an increased number of earthquakes. Seismicity at Mount St. Helens has declined significantly since yesterday. However, small, shallow earthquakes are still occurring at above typical background rates. We will continue to monitor the situation through the weekend.

This message supersedes the Information Statement below. U.S. Geological Survey, Vancouver, Washington University of Washington, Pacific Northwest Seismograph Network, Seattle, Washington Mount St. Helens Information Statement September 24, 2004 10:00 AM, PDT Since about 2 am PDT on the morning of 09/23 an earthquake swarm has been occurring at Mount St. Helens.

Through 5 P.M. PDT on 09/23 about 200 small (less than magnitude 1) earthquakes have been located at MSH, and many smaller events have also been recorded through this morning. The earthquakes are occurring at shallow depths (less than 1 kilometer, or 1/2 mile) mostly under the lava dome that formed between 1980 and 1986. Such earthquakes are common at MSH, but a swarm with this many earthquakes has not been recorded for several years, most recently on November 3-4, 2001. The cause of such shallow swarms is uncertain, but may reflect increased ground water levels with the onset of autumn rain. The probability of small steam explosions that hurl rocks a few hundred meters (yards) may also be increased during periods with increased shallow earthquakes.

Prior to the 2001 swarm, the last period of increased earthquake activity at Mount St. Helens occurred in the spring and summer of 1998 when hundreds of earthquakes per month, most smaller than M=2, were detected at depths as great as 9 kilometers (6 miles). An intrusion of magma (or molten rock) deep under the volcano and resulting increased gas pressure in the conduit that leads to the lava dome likely caused this increase in earthquakes. The current swarm is different in that the events are typically much smaller and shallower.

We see no evidence that an intrusion of magma similar to that of 1998 is underway. We continue to monitor the situation closely and will issue additional Updates as warranted. Daily updates of earthquake data and other information can be found on the WORLD WIDE WEB at URL: http://<br /> <br /> <a href="http...ntActivity</a> (CVO Menu - Monthly Summaries) and http://www.pnsn.org/HELENS/welcome.html (University of Washington - Seismic Update)

[39mto39g]

seen this on the news this morning, I don't belive telling people twice in that area will be nesessary. See the snow melting on the mountain? leave, end of story. (or die)

Ron

[Keith_Hixson]

The big eruption occurred May 18, 1980.
Don't expect another major eruption for a couple thousand years. However, smaller eruption can occur at anytime. Usually they take about three or four months to develop. They aren't all that concerned about these earthquakes at this time. If they continue for several months then we'll know something is on its way, but nothing like 1980.

St Helens is quite isolated, basically a few summer homes etc. in the area. Not an extreme danger to anyone except a small handful of people. Elk, deer, fish might want to get out!

Keith

[Jerry D]

It's Mt Ranier I would be worried about . I lived under it's shadow for 12 years and as long as the snow cap looked solid I also took heart that it was OK but like the reporters at Channel 13 always said If you live in the Mud Slide/ Flood plain look out for Mt Ranier!

[Keith_Hixson]

Jerry,

You got that right! Mt Rainier and its mud slides and pyroclastic flows could wipe out a couple hundred thousand people in the the Olympia to Seattle area. However they monitor those volcanoes very close. I'm sure with modern technology there will be plenty of warning. Even St. Helens had plenty of warning. Yep, Ft Lewis and McCord Air Base look right up the throat of Mt Rainier.

Keith

[82Rigger]

Okay, I know about hurricanes, but not much about volcanoes.

Why is Mt Ranier a present concern? :cd:

[Keith_Hixson]

Mt. Rainier is a 14,410 Volcano in Western Washington. Several rivers from Olympia, WA to Seattle, WA begin on the slopes of Mt. Rainier. Areas around Tacoma, Seattle, and Olympia with rivers that come off Mt. Rainier could easily have major mud flows of over 100 ft above flood level. These mud flows happen almost instantly after an erruption and flow at amazing speeds. The Auburn Valley, Puyallup Valley and Nisqualley Valley could all be covered with mud from Mt. Rainier in fifteen minutes to an hour after an eruption of Mt. Rainier. Mt. Rainier hasn't had a sigificant eruption for 130+ years. Mt. Rainier is one of the snowiest places on earth. Mt. Rainier is one of the most glaciated peaks in the world. All that water and mud could come zooming down that mountain bury hundreds of thousands of people with fifteen to an hour after an eruption.

However, Mt. Rainier hasn't shown any signs of major activity but neither did Mt St. Helens before its eruption. However earthquake activity before an eruption usually last for month or two before the major eruption. All scientists agree that eventually Most of the Volcanos in the Cascade Range will erupt eventually. The most dangerous is also the largest and closest to major metropolitan areas of Seattle, Tacoma, and Olympia, that being Mt. Rainier.

Keith

P.S. I hope this makes sense.

[82Rigger]

Keith,

Yeah, that makes sense. Thank you.

So, in a nutshell, the problem is Mt Rainier's location relative to populated areas.

So, there's been no recent eruptive or seismic activity?

I know what pyroclastic flow is. That's what killed the people in Pompeii and Herculaneum.

Isn't there a name for those eruption-generated mudslides..."lahar" or something like that?

I am amazed by the amounts of ash, pumice, and other ejecta that can be loosed by a volcano. CUBIC MILES of the stuff, I understand.

[Keith_Hixson]

Mt. Rainier, is one of the largest land based Volcanoes in the World. It's base is at about 1,000 feet elevation. It's official height is 14,410 ft. That's one massive hill. For years it held the world record for most snowfall in one winter season, so it has miles and miles of snow and glaciers on its sides year around. A sudden warming of the volcano and eruption could create mudslides up to 100 ft. + deep in the rivers that flow from its slopes. That would cover up cities or portions of cities like, Auburn, Kent, Puyallup, Tacoma, and some small towns in the Olympia area. The other major volcanoes in the Cascade range aren't that close to human population. Mt. Baker near the Washington, Canadian Border could also cause some serious problems as it is near some significant population and is very heavily glaciered.

Volcanoes usually only erupt every 100 plus years. Most of our volcanoes in the Cascades haven't erupted for 600 years or more. Those hurricanes just keep coming through. You usually will have a two or three months warning of a major event. I think I'd rather take my chances with volcanoes than hurricanes.
Lasson in Calif. had eruption at the turn of the last century, Rainier had a small eruption in 1880 or near that date. But they do erupt on occassion. Scientist say it is just a matter of time.

Keith

Keith

[82Rigger]

What determines if a volcano is ACTIVE or DORMANT?

Recent seismic activity?

Recent eruptive activity?

Or something else?