Active volcanoes / Aktive vulkaner:

Mount Saint Helens, USA  




 

There has been written so much about the 1980 eruption that we have decided not to include
that event on our pages. A search on the Internet will give several hundred pages and pictures
from that now so famous eruption.
So what we do here, is to start with what might become the next big explosion - or just to
follow what happens in the meantime....

See also our Web-Cam page: Click here!
Latest news from USGS: Click here!
Latest Earthquake info: Click here!


Friday, March 11th, 2005
The volcano is clear yesterday morning and sporting an intermittent steam plume. There have
been no explosive events since 5:25 p.m. local time on Tuesday. After the event Tuesday,
seismicity returned to a level similar to that in the several hours prior to the explosion,
and it remains at about that level at this time. Yesterday, the new dome was found to be
remarkably intact. Ballistics up to ~1 m in diameter were hurled as far as the northern flank
of the old dome. No ballistics were found along or beyond the crater rim. Ash deposits were
found along a narrow eastward swath. Ash up to ~1 inch thick was deposited along the east
flank of the volcano. Although no obvious vent was observed, the distribution of ballistics and
ash suggest the explosion emanated from a source very near that of the October 1, 2004 and
January 16, 2005 explosions. Today, crews will conduct more visual observations, measure
gases, do routine maintenance on some far-field instrument stations, and redeploy GPS units.

Tuesday, March 8, 2005, 6:00 P.M. PST

A small explosive event at Mount St. Helens volcano began at approximately 5:25 p.m. PST.
Pilot reports indicate that the resulting steam-and-ash plume reached an altitude of about 36,000
feet above sea level within a few minutes and drifted downwind to the east-northeast.
The principal event lasted about 30 minutes with intensity gradually declining throughout.
The USGS Cascades Volcano Observatory lost radio signals from three monitoring stations in
the crater soon after the event started. The cause of the outage won’t be known until scientists
can visit the crater tomorrow to assess the situation, weather permitting. The event followed
a few hours of slightly increased earthquake activity that was noted but not interpreted as
precursory activity. There were no other indications of an imminent change in activity.

Wednesday, December 15th, 2004
Fueled by hot rock coming from below, the lava dome has risen to about 1,000 feet above the crater floor. The dome is now about 1,500 feet long and 800 feet wide and is broken roughly into three segments, with the central segment rising faster than the others.

The risk of collapse depends on how fast and how steeply the dome continues growing. Studies of other volcanoes show that lava domes can rise for years if there is relatively little new rock fueling the eruption. At Mount St. Helens, 5 cubic yards - a small truckload - of hot rock has been coming out of the ground every second.

After the 1980 eruption, a lava dome grew for six years, occasionally collapsing. The new dome lies to the south of the old dome. The force of its growth has pushed a large glacier - 600 feet thick in places - against the crater wall.

There at at present several active volcanoes where the dome is growing, but as here nobody knows when or if there will be a violent eruption. It might last for years. We are therefore not updating these volcanoes, except when there is a notable change in the activity. So also for St.Helens.

Thursday, December 9th, 2004
High wind, rain, and snow from a large storm are wreaking havoc with field-sensor telemetry. Some seismic stations show considerable noise, and some signals are temporarily dropping out. The ongoing sequence of small (mostly less than M1.5) earthquakes continues, and no new large (>M2.5) quakes have been recorded within the past 24 hours. A single GPS station high on the outer southeast flank of the volcano (~7300 feet) shows about 2 cm (1 inch) of progressive southeastward movement over the past 3 weeks. This minimal movement, apparently in response to new lava impinging on the southeast crater wall, is an expected consequence of the nature of the dome growth occurring in the crater. USGS

Monday, December 6th, 2004
Latest from USGS at 17.20 UTC:
Overnight, three large earthquakes of about magnitude 3 occurred amidst the ongoing sequence
of smaller (mostly less than M1.5) earthquakes. This mini-burst of large earthquakes is similar to
others that have occurred episodically in the past several weeks. Such a pattern represents
nothing unusual in the expected sequence of events accompanying lava-dome growth.


 
From the Volcano Webicorder at June Lake this morning.

Another quake hits at 15:23 UTC (07:23 local time), probably same size as the two below.
An earthquake with magnitude 2.9 hit the center at 02.59 UTC this morning (yesterday evening local time). Another quake at 08.49 UTC seems to be of same size, but is still
not confirmed.

Thursday, December 2nd, 2004
From photographs taken on Monday, we now know that the GPS instrument, or Spider, that had
been riding along on the new lava dome since November 20 is lost. The crumbling southwest
margin of the dome probably neared the Spider on Saturday, radio communications became
intermittent, and were lost on Sunday when the Spider evidently fell off the cliff into the talus
below. In its week-long journey it moved about 75 meters (250 feet) south-southeastward
and about 8 meters (26 feet) upward.

Mount St. Helens has been pumping out up to 250 tons of sulfur dioxide a day. At its worst,
that's a rate more than double the amount of sulfur dioxide produced by all the state's industries
combined, according to several US-newspapers today. The volcano has been Washington's top polluter since its newest erupting began in early October. And a state official says there's nothing anybody can do about it, because, in his words, "You can't put a cork in it."

Wednesday, December 1st, 2004

From the east, view of the glacier uplift agains the south crater wall.
USGS Photograph taken on November 29, 2004, by Jim Vallance and Matt Logan.

The lava emerges from the vent with enough strength that it can push earlier-extruded lava
southward toward the crater wall. The leading edge of the extrusion has now reached the crater
wall, so it will be interesting to see what happens over coming days. Will new lava start to well
upward over the vent and piggyback on the south side of the 1980s dome rather than continue to
push against the buttress provided by the crater wall? Or will new lava move eastward or
westward in a pattern similar to its southward movement?

Tuesday, November 30th, 2004

Looks like we had another one about 04.10 UTC today.

Three earthquakes between magnitude 2.6 and 2.8 occurred last evening and early yesterday
morning amidst the ongoing sequence of smaller (mostly less than M1.5) earthquakes.
Along with Saturday’s M3.1 event and similar-sized earthquakes that occurred in mid-November,
they represent nothing unusual in the expected sequence of events accompanying lava-dome
growth.
USGS

Sunday, November 28th, 2004
USGS report from Saturday 10:15 am PST (1815 UTC)
Mount St. Helens crater and dome from the east.
USGS Photograph taken on November 26, 2004, by John Pallister

Aerial views taken late yesterday afternoon show that growth of the welt and lava dome continue.
Most of the east arm of the crater glacier that is adjacent to the welt is now deformed.
Ice close to the welt is steeply inclined and intensely fractured; farther away the ice surface is
beginning to rumple into broad ridges as the welt grows eastward.


From the 'Short-Period Weak-Motion Webicorders ' yesterday morning
when the 3.1 magnitude quake occured.

A magnitude 3.1 earthquake occurred at a shallow level in the crater about 5 a.m. this morning
--the first earthquake greater than M3 that has been recorded since the new lava dome
emerged in mid-October. It appears to be a larger version of the small earthquakes that have
been occurring for many weeks at the rate of about one per minute.

Tuesday, November 23rd, 2004

Mount St. Helens' new growth, from the south.
USGS Photograph taken on November 20, 2004, by Dan Dzurisin.

The steep west face of the dome is crumbling piecemeal, but, as fractures grow, there is an
increasing chance of large slabs of hot rock toppling westward and forming ash clouds that
drift out of the crater and hot avalanches, or pyroclastic flows. The flows would sweep over,
erode, and melt snow and ice and produce lahars, or volcanic debris flows, that pour northward
out of the crater onto the Pumice Plain.

The three instrument packages, called Spiders, that were lowered from a helicopter into the
crater on Saturday are operating well and sending back data in real time. The GPS site placed
near the top of the new lava dome is moving at an impressive rate southeastward and upward.
In 24 hours it moved about 10 meters (33 feet) southeastward and 2 meters (6.5 feet) upward,
confirming visual and photographic observations.

Gas measurements made on Saturday were of high quality and show that daily gas emissions
remain at a more or less constant rate of a couple hundred tons of sulfur dioxide, about 1000
tons of carbon dioxide, and several tons of hydrogen sulfide.

Monday, November 22nd, 2004
Saturday’s clear, calm weather, coupled with a relatively low level of steaming, created ideal
conditions for observations and instrument installations. Thermal-imaging and geologic
observations revealed further expansion of the welt, the broad area of uplift south of the
1980-86 lava dome, toward the southeast and development of several deep pits on the
uplift that may be the result of melting of blocks of glacier ice and collapse of overlying debris.

Three instrument packages called Spiders, two with GPS instruments and one with a seismometer,
were lowered from a helicopter. One GPS sits near the top of the new lava dome. Processing of
the first several hours of data, showed that the highest point on the new lava dome is at an altitude of 2256 m (7400 ft), or about 76 m (250 ft) higher than the summit of the 1980-86 lava dome.

Hopefully this instrument can survive in its harsh environment and allow us to track movement of
that point in real-time, both horizontally and vertically. This will provide a method for assessing
how lava-dome growth is progressing. The new seismometer is located on the upper east side
of the old lava dome and will help in obtaining better locations of earthquakes. USGS

Saturday, November 13th, 2004


Mount St. Helens' new growth as seen from the east.
USGS Photograph taken on November 12, 2004, by Willie Scott


Aerial view of Mount St. Helens' crater and lava dome, as seen from the west.
USGS Photograph taken on November 10, 2004, by John Pallister.

No changes in activity yet.

Friday, November 12th, 2004
Yesterday field crews conducted visual and thermal-imaging observations and a gas-sensing flight.
Strong winds made interpretation of gas data difficult. Good viewing conditions revealed
continued growth of the lava dome. Current estimates are that the welt, the broad area of
deformation, is about 600 m (about 1950 feet) in diameter. The new lava dome, which occupies
the central and western parts of the welt, is about 400 by 180 m (1300 by 600 feet).

The highest point on the new lava dome is about 250 m (820 feet) above the former surface
of the glacier that occupied that point in mid-September. Maximum surface temperatures on the
new dome remain at about 700 degrees C (1300 degrees F). GPS instruments on the welt show
rates of movement of up to several meters per day, while GPS instruments on the 1980-86 lava
dome show movements of up to 1-2 cm (less than one inch) per day northward, away from the
growing welt and new dome.


View of the crater with the new dome in the background..
USGS Photograph taken on November 7, 2004, by John Pallister

Wednesday, November 10th, 2004
The latest estimate of the volume of the uplifted area and new lava dome from detailed analysis
of aerial photographs taken on 4 November is about 20 million cubic meters (26 million cubic
yards). This compares with volumes of about 5 million cubic meters on 4 October and 12 million
cubic meters on 13 October. The apparent decrease in rate of volume change (7 million cubic
meters in the earlier 9-day period versus 8 million cubic meters in the later 22-day period)
doesn’t take into account millions of cubic meters of glacier ice that have been removed from a
large part of the area of uplift. Work is underway to assess this effect. The 20-million-cubic-meter
volume of the new uplift and lava dome is now more than 25% of the volume of the lava dome
that grew in the crater between 1980 and 1986.

Tuesday, November 9th, 2004

Night shot of new growth on Mount St. Helens' lava dome, as seen from Johnston Ridge Observatory (JRO).
USGS Photograph taken on November 5, 2004, by Elliot Endo


Closeup view of Mount St. Helens new growth, from the northwest.
USGS Photograph taken on November 7, 2004, by John Pallister

A dome of brilliantly hot rock at the volcano's summit grows bigger every day - by as much
as a dump-truck load a second, according to U.S. Geological Survey. At night, the 1,300
degree-Fahrenheit rock glows.

But the expanding lava dome and its fiery temperature don't signal an explosive eruption.
Rather, USGS predicted that the volcano will continue to ooze hot rock for months,
a continuation of the slow eruption begun 48 days ago.

Monday, November 8th, 2004


Mount St. Helens' dome, and new growth, from the west.
USGS Photo November 4, 2004, by Jim Vallance and Matt Logan.

Growth of the new lava dome inside the crater of Mount St. Helens continues, and is
accompanied by intermittent emissions of steam and ash.

Although considered less likely at this time, the current eruptive activity could evolve into a more
explosive phase that affects areas farther from the volcano and sends significant ash thousands of
feet above the crater where it could be a hazard to aircraft and to downwind communities.
(which means we will continue to monitor - and update - untill it calms down again)

Visibility is excellent at present. A steam plume is rising passively and drifting northward out of
the crater. The plume occasionally contains minor ash, which falls out in the crater and on the
flank of the volcano, darkening the snow.


Top of Mount St. Helens new growth, vent area, and broken glacier ice, as seen from the west.
USGS Photograph taken on 27 October 2004, by David Wieprecht.

Seismicity remains at a low level compared to that observed early in this unrest. The current
seismicity is consistent with a continuing, slow rise of magma driving uplift of the crater floor
and feeding a surface extrusion of lava. The overall low rates of seismicity and gas emission
suggest that the lava reaching the surface is gas poor, thereby reducing the probability of highly
explosive eruptions in the near term.

For previous reports on St.Helens: Click here.



 

 

  
Before - and after the explosion

 
Not many trees standing up any longer....


http://www.usgeology.com/eruptiontypes.html


Ash-deposits from St. Helens May 18th, 1980, measured in millimeters.


BEFORE/AFTER #2: Mount St. Helens and the devastated area is now within the 110,000-acre Mount St. Helens National Volcanic Monument, under jurisdiction of the United States Forest Service. Visitor centers, interpretive areas, and trails are being established as thousands of tourists, students, and scientists visit the monument daily. Mount St. Helens is once again considered to be one of the most beautiful and interesting of the Cascade volcanic peaks. (May 19, 1982, by Lyn Topinka, USGS/CVO)

 

Linker:
 Mount St.Helens A General Slide Set by Lyn Topinka, USGS/CVO/WRD

Google
 
Web www.vulkaner.no




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ANIMALS

over 250

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BIRDS

over 500

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FLOWERS

over 225
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SEALIFE
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TRAVEL
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VOLCANO


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