Vulkaanuitbarsting Mount St.Helens

Bron: CNN

Scientists watching unusual events near volcano



Series of earthquakes could signal eruption of Mount St. Helens

VANCOUVER, Washington (CNN) -- A series of unusual earthquakes near Mount St. Helens in recent days has scientists warning that something more serious could be imminent.

The "hazardous event" the U.S. Geological Survey warns is possible could be an explosion caused by steam building up inside the volcano, or it could be more serious -- involving molten rock and deadly gas.

The quakes are occurring less than a mile below the surface of an 876-foot-tall lava dome within Mount St. Helens' crater. Some of them are of a type that indicates the presence of pressurized fluids or magma, the USGS and the University of Washington Pacific Northwest Seismograph Network in Seattle said Monday in a joint statement.

"We're still thinking it's not likely to be anything real big," said Tom Pierson, a USGS research scientist at the Cascades Volcano Observatory in Vancouver. "We're not real worried. [The seismic activity is] very interesting to us because it's unusual."

A group of very small, shallow earthquakes, called a "swarm" by seismologists, began Thursday morning and peaked about midday Friday, Pierson said, then slowly declined through Sunday morning. Those quakes were all less than magnitude 1.0.

But since then, more than 10 earthquakes with a magnitude between 2.0 and 2.8 have been recorded, according to the notice issued Monday.

"They're all pretty small magnitude," Pierson said. "Maybe that largest one, you might feel if you were pretty close by."

Still, that's the most earthquakes recorded in a 24-hour period since October 1986, when Mount St. Helens had a minor eruption that added to the lava dome that began forming after the catastrophic eruption of May 18, 1980. That eruption blew out the side of the mountain, killing 57 people and deforesting 230 square miles.

Yet scientists cannot rule out the possibility of a more serious eruption, he said. An aircraft will soon fly over the lava dome to test for the presence of carbon dioxide and sulfur dioxide, signs that magma might be building up.

Similar earthquake swarms were recorded in 1998 and 2001, but no explosion occurred in either year, Pierson said.

The U.S. Forest Service, which manages the park on Mount St. Helens, has closed areas around the crater and the volcano's outer flanks to hikers.

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Info & Geschiedenis
Mount St. Helens is een grote nog actieve vulkaan. Een compositevukaan, ook wel stratovulkaan genoemd. Deze vulkanen zijn typisch stijl aan de zijden, een soort symmetrische kegels. Ook Mount Hood een andere vulkaan dicht bij Portland is een compositievulkaan. Mount Hood is een actieve vulkaan, evenals Mount St. Helens, welke elk moment kan uitbarsten tussen nu en zeshonderd jaar. Als deze vulkaan uitbarst zal heel Portland bedolven worden onder lava en hete as. Ook Mount Rainier vlak naast Mount St. Helens en Mount Fuji in Japan zijn compositievulkanen.

Compositievulkanen hebben over het algemeen een krater. Mount St. Helens had een krater welke werd dichtgemaakt door aardverschuivingen en een Magma staaf die de krater bij wijze van spreken uitdeukte. Mount St. Helens is ook een zogenaamde Subduction-zone vulkaan. Zulke vulkanen zijn explosief omdat het magma te stijf is om makkelijk weg te vloeien. Zo'n vulkaan komt tot ontploffing net als je je hand op een koolzuurhoudend drankje doet, schud en dan snel loslaat.

Louwala-Clough is de indiaanse naam voor Mount St. Helens, wat rokende berg betekent. Volgens een legende was de berg eens een mooie meid, "Loowit" genaamd. Toen twee zonen van de grote geest "Sahale" verliefd op haar werden, kon ze niet kiezen tussen de twee. De twee moedigen, Wyeast and Klickitat vochten om haar, dorpen en bossen begravend in het gevecht. Sahale was razend. Hij gooide de drie geliefden uiteen en een machtige berg rees waar een ieder viel. Omdat Loowit mooi was, was haar berg (Mount St. Helens) ook mooi, symmetrisch steen van verblindend wit. Wyeast (Mount Hood) heft zijn hoofd in trots, maar Klickitat (Mount Adams) huilt omdat hij de mooie meid, omhuld met sneeuw wil zien, daarom buigt hij zijn hoofd terwijl hij in de verte naar St. Helens staart.

Zondag 18 mei 1980.
Wat weer een zonnige rustige dag had moeten worden, veranderd in een catastrofale ramp.

Mount St. Helens in de staat Washington behoort tot de bergketen The Cascades genaamd. Deze strekt zich uit vanaf grens met Canada in de staat Washington tot 1125 km verder in Californie, waar ze aansluiten op de Sierra Nevada bergketen.
In deze bergketen komen vele vulkanen voor welke zo'n 90 miljoen jaar geleden gevormd werden. Een van die vulkanen is Mount St Helens. Mount. St. Helens ligt ongeveer tussen Portland (Oregon) en Seattle (Washington).

Op 18 mei 1980 barstte de 2949 m. hoge Mount St. Helens vulkaan plotseling uit met een kracht van meer dan 500 atoombommen van het formaat waarmee Hirosjima en Nagasagi in augustus 1945 werden verwoest. Deze kracht in ongeveer te vergelijken met 400 miljoen ton TNT (springstof). De bovenste 398 meter werd van de top weggeblazen en liet een spoor van vernielingen achter Steden in de omgeving waren dagen lang bedekt met een dikke laag as. De aswolk steeg meer dat 25 km omhoog de strak blauwe lucht in. Deze aswolk heeft het weer rond de vulkaan zeer beïnvloedt.

Nna 10 jaar is de verwoesting nog steeds waarneembaar, maar toch is de natuur zich al aan het herstellen. Dat is het mooie van de natuur. Ondanks dat er een verwoestende kracht van die zelfde natuur iets vernield achterlaat, weet het toch na jaren weer op te krabbelen. Er leven weer dieren, er begint weer flora te verschijnen. In 1982 is het park een Nationaal Monument geworden. Er zijn namelijk mensen tijdens de uitbarsting vermist geraakt en nooit gevonden.

Een documentaire met een enorme impact, al is het beeld waarschijnlijk lang zo indrukwekkend niet als de werkelijke berg. Deze kun je natuurlijk ook bezoeken. Op discovery channel is lange tijd de Documentaire gedraaid en het filmpje van de daadwerkelijk explosie van de berg is dan ook indrukwekkend.

Foto van de berg VOOR de eruptie:


Foto van de berg NA de eruptie


Meer informatie over Mount St.Helens op ---> http://www.fs.fed.us/gpnf/mshnvm/
en ook een interessante Nederlandse link ---> http://www.verenigdestatenvanamerika.com/reisverhalen/wj01.html

quote:

Op dinsdag 28 september 2004 13:37 schreef -CRASH- het volgende:
M.ST.Helens was zeker indrukwekkend
maar vergleken met Krakatoa... een "kleintje"

On the 26th August 1883,
Krakatoa, off Java, exploded, destroying the island.
The explosion was heard in Australia, 4,800 km away,
while the dust cloud circled the Earth,
causing the Moon to turn 'blue' in Britain.

[afbeelding]

Klopt inderdaad... dat was een nog veel zwaardere explosie/uitbarsting
maar toen was er nog niet echt nieuwsberichten over de wereld, zoals TV etc...
1980 wat dat betreft staat meer in het geheugen gegrift.

Update van Dinsdag

Quakes Still Rippling Across Mount St. Helens
Tuesday, September 28, 2004

SEATTLE — Small earthquakes rattled Mount St. Helens at the rate of one or two a minute Monday, and seismologists were working to determine the significance of some of the most intense seismic activity in nearly 20 years.

Early tests of gas samples collected above the volcano by helicopter Monday did not show unusually high levels of carbon dioxide or sulfur.

"This tells us that we are probably not yet seeing magma moving up in the system," said Jeff Wynn, chief scientist with the U.S. Geological Survey (search) in Vancouver, Wash. He noted additional tests are necessary to better define whether there's magma moving under the mountain's crater.

Scientists are trying to figure out what is going on beneath the 925-foot-high dome of hardened lava within the mountain's gaping crater. They want to know whether the quakes are the result of water seeping into the mountain or magma.

In either case, they'll continue to watch the volcano — which erupted to devastating effect in 1980 — from the Cascade Volcano Observatory (search) in Vancouver, about 50 miles away. Additional flights are also planned but not yet scheduled, Wynn said.

A helicopter carried scientists and instruments over the crater Monday to assess the gases and ground deformation that would indicate pressure building below the dome.

Waarschuwing voor uitbarsting Mount St.Helens

Uitgegeven: 30 september 2004 07:18

SEATTLE - Amerikaanse wetenschappers hebben woensdag gewaarschuwd voor de mogelijke uitbarsting van de vulkaan Mount St.Helens in de Amerikaanse staat Washington.

De "kleine tot middelgrote" eruptie zal mogelijk binnen enkele dagen plaatshebben, aldus de geologen. De laatste grote uitbarsting van de vulkaan was in 1980. Toen kwamen 57 mensen om het leven.

Mount St.Helens

VANCOUVER, Washington (CNN) -- The U.S. Geological Survey issued a volcanic advisory Wednesday for Mount St. Helens with officials warning of a heightened possibility of a small to moderate eruption.

There was no immediate timetable for when an eruption could occur.

Geologists at the Cascades Volcano Observatory said the area could remain under the volcanic advisory for days or even weeks.

"We think there is a heightened possibility that we could see an explosion," said Cynthia Gardner, acting scientist in charge at the observatory. "We are expecting that either nothing could happen or perhaps we could have an explosive event."

She said if a small to moderate eruption occurred, rocks could be hurled up to 3 miles from the volcanic dome and ash could spew up to 10,000 feet in the air and be carried about 10 miles downwind.

"The concern there is an ash and aviation hazard," she said, noting that volcanic ash can clog a plane's engine and cause other problems.

The U.S. Forest Service has closed access into the crater and access to areas above 4,800 feet around Mount St. Helens. Trails on the north side of the crater have been closed.

The advisory that was issued is the third of four levels -- with the fourth being eruption.

Hier trouwens een link naar een webcam.. http://www.fs.fed.us/gpnf/volcanocams/msh/

SEATTLE — The flurry of earthquakes at Mount St. Helens (search) intensified further Thursday, and one scientist put the chance of a small eruption happening in the next few days at 70 percent.

Jeff Wynn, chief scientist at the U.S. Geologic Survey's (search) Cascade Volcano Observatory in Vancouver, Wash., said tiny quakes were happening three or four times a minute. Larger quakes, with magnitudes of 3 to 3.3, were happening every three or four minutes, he said.

New measurements show the 975-foot lava dome in the volcano's crater has moved 2 1/2 inches to the north since Monday, Wynn said.

Small Eruptian, Smoke rock Mount St.Helens



VANCOUVER, Washington (CNN) -- Scientists are closely watching Mount St. Helens after a small eruption spewed smoke and ash thousands of feet Friday before another earthquake rattled the volcano.

A series of small earthquakes was detected in the week before the Friday afternoon's eruption. This seismic activity decreased shortly after the noon (3 p.m. ET) eruption, but picked up again within hours.

Peter Frenzen, a scientist with the Mount St. Helens National Volcanic Monument, said a 2.0 magnitude earthquake was detected.

One scientist described the eruption as a "hiccup."

The volcano spewed a harmless plume of steam and ash into the air Friday, the biggest eruption by the volcano in 18 years.

A small explosion was detected on the south side of the volcano's lava dome, where cracks had been detected in a glacier, said John Major of the U.S. Geological Survey.

The mountain then vented a combination of steam and ash for 24 minutes, sending a pale gray column nearly 10,000 feet into the blue Washington sky.

"There is no indication that magma has reached the surface," Major said.

Molten rock is called magma before reaching the surface where it then becomes lava.

Scientists said the presence of magma could indicate the potential for a more serious eruption.

Geologist Tom Pierson said the event "was really a hiccup. [Eruptions] could be a little bigger once real magma is involved."

A visible plume -- which was mostly steam but contained some ash -- moved southwest about six miles, Major said.

The Portland, Oregon, metropolitan area lies about 50 miles southwest of Mount St. Helens.

er staat een filmpje op de website van Fox News genaamd :"there she blows"...
Typisch Amerikaans dat er eerst reclame komt over de presidentsverkiezingen en dan het nieuwsfilmpje over de uitbarsting. ---> http://www.foxnews.com/story/0,2933,134186,00.html

Mount St. Helens ready to Blow: Eruption Imminent

MOUNT ST. HELENS NATIONAL MONUMENT, Wash. — Mount St. Helens stewed in volcanic gases and low-level earthquakes Sunday, with crowds of eager tourists hoping to glimpse an eruption that scientists said could happen immediately or take a few weeks.

A second long tremor early Sunday and an increase in volcanic gases strongly suggest magma is moving inside, researchers from the U.S. Geological Survey said. The mountain's alert was raised to Level 3, the highest possible, after a volcanic tremor was detected Saturday for the first time since before the mountain's 1980 eruption.

I don't think anyone now thinks this will stop with steam explosions," geologist Willie Scott said Sunday at the Geological Survey's Cascades Volcano Observatory in Vancouver, Wash., about 50 miles south.

But Scott said scientists discussed lowering their alert from a Level 3 "volcano advisory," which indicates eruption is imminent, to Level 2 "volcanic unrest," which indicates an eruption is possible. They needed more data before making any change, he said.

"What we haven't gotten back today yet is a lot of field measurements — there's a gas flight going on, a flight to use thermal imaging to look at the [lava] dome, GPS data needs to be downloaded," Scott said Sunday. "There's a lot of work that needs to be done. That will occur overnight and tomorrow morning."