Naam en Gegevens
Mount St Helens, de 'St. Helensberg', is een vulkaan in Skamania County, Washington, VS. De berg maakt deel uit van de Cascade Range. Hij stond bij de Indianen bekend als Louwala-Clough wat "rokende of vuurberg" betekent in de taal van de Klickitats. In het Engels is de berg naar de Britse eerste Baron van St. Helens vernoemd, nadat een Brits team het gebied in kaart had gebracht.
Hoogte = 2550 m (nu dus
) Coördinaten= 46° 12' 28" N, 122° 11' 39" W
Ligging = Cascade Range, Washington State, (VS)
Eerste Beklimmer = 1853, Thomas Dryer
Type Vulkaan = Actieve stratovulkaan
Laatste eruptie = 1987
(bovenstaande gif speelt zichzelf vier keer, daarna moet je de pagina verversen. Geeft de tijd weer tussen 1973 en 2000)
Net als de meeste andere vulkanen in de Cascade Range is Mount Saint Helens een stratovulkaan, die opgebouwd is uit verschillende lagen lava, puim, as en andere afzettingen. Strato betekent lagen in het Grieks. Mount Saint Helens heeft lagen van basalt, andesiet en ook wat lagen met daciet. De weggeblazen top van de berg bestond uit daciet. De lava van de vulkaan is zeer dik en stolt zeer vlug.
DE FILM - PICTURE FOR PICTURE
http://video.google.com/videoplay?docid=3977416382972126736
Zie hier de schokkende uitbarsting van St.Helens en de grootste aardverschuiving in de geschiedenis...in picture-for-picture...
Bekendheid en Geschiedenis
De vulkaan staat vooral bekend vanwege de grote uitbarsting op 18 mei 1980
In Maart 1980 werd het USGS wakker geschud door een serie aardbevingen (100 in een week) die erop duiden dat er 'iets goed mis was' onder/in Mt.St.Helens. In de weken na 20 maart werd duidelijk dat Mount St.Helens zich wel eens kon opmaken voor een uitbarsting. Seismologen hielden de berg dag en nacht in de gaten. In April werd duidelijk dat er een geweldige klap ging komen omdat een 'bult' zich begon te vormen op de hellingen van St.Helens. Deze 'bult' leek met de dag groter te worden en begin Mei 1980 werd er algeheel alarm geslagen over een potentiele gevaarlijke uitbarsting. Van overal in de wereld kwamen toeristen naar het gebied en in de dagen voor de 18e namen de trillingen en kleinere uitbarstingen af en leek de vulkaan stil te worden. Maar op 18 mei ging het dan alsnog gigantisch mis...
Dat was de meest dodelijke en verwoestende vulkaanuitbarsting in de geschiedenis van de Verenigde Staten. 57 personen kwamen om het leven en 200 huizen, 47 bruggen, 24 km spoorweg en 300 km weg werden vernield. De uitbarsting werd voorafgegaan door een beving van 5,1 op de schaal van Richter en blies de top van de berg, waardoor deze 400 m lager werd.
Mount St.Helens VOOR de uitbarsting van 1980
Mount St.Helens NA de uitbarsting van 1980
De kracht ervan was vergelijkbaar met 500 maal de kracht van de atoombom op Hiroshima. Voordat de eigenlijke eruptie plaatsvond steeg een enorme pliniaanse wolk uit de kratermond. Een grote pyroclastische wolk, met een temperatuur van rond de 500 graden Celsius, verwoestte alles op zijn weg naar beneden. Er ontstond een flinke krater (caldera). Tot in de wijde omtrek werden de bomen platgegooid en de omgeving werd "gezandstraald" over een oppervlak van ca. 600 km². Onbeschermde personen die door deze pyroclastische stroom werden overvallen, werden binnen enkele tellen levend gekookt. Als de vulkaan niet in een zeer dun bevolkt gebied had gelegen had het aantal slachtoffers enorm kunnen zijn. De vulkaan was al lang niet meer actief geweest, maar er zijn sinds de ontdekking in de achttiende eeuw wel een aantal kleinere uitbarstingen geweest.
Mt.St.Helens na 1980, nu en de toekomst?
In 1982 werd het hele Mt.St.Helens gebied (110.000 acres) tot Nationaal Monument verklaard door de Amerikaanse regering en wordt sindsdien overspoeld door toerisme en wordt gebruikt voor het onderzoek naar/gevolgen van de ontploffing van mei 1980
In september 2004 begon de berg opnieuw te roken, maar een grote uitbarsting bleef achterwege. Op 8 maart 2005 stootte de vulkaan een ruim 10 km hoge wolk van as en stoom uit, gevolgd door een lichte aardbeving met een kracht van 2,5 op de schaal van Richter. De rookwolk die ongeveer een half uur aanhield was vanuit de wijde omtrek zichtbaar. Nog altijd rookt de berg en rommelt het... seismologen zijn er nog altijd niet uit wat er gebeurd en houden de berg nauwlettend in de gaten .
Het opmerkelijkste nieuws kwam misschien wel in Mei 2006 waaruit bleek dat dagelijks er een stuk 'rots' uit de krater omhoog rees, dagelijks kwam er ca 1,5 meter bij (zie foto 5 mei)
5 mei 2006
Deze 'rots' stortte uiteindelijk ineens maar gaven genoeg bevestiging dat de hele berg in beweging is en dat er mogelijk iets op stapel staat want ook wordt er langzaam maar zeker weer een 'bult' gevormd op de flanken van St.Helens.
Een herhaling wordt niet uitgesloten,maar wordt ook niet op korte termijn verwacht.
6 december 2006
Links
Live Cam van Mt St.Helens --> http://www.fs.fed.us/gpnf/volcanocams/msh/
Huidige status --> http://vulcan.wr.usgs.gov/Volcanoes/MSH/
The Road to Eruption ---> http://vulcan.wr.usgs.gov(...)sWeek/framework.html
Foto's, Informatie en Video-/Beeldmateriaal --> http://volcano.und.edu/vwdocs/msh/
Website van 'nu' --> http://www.kirotv.com/mountsthelens/index.html
Video van het nieuws en de ontploffing van mei 1980 --> http://www.kirotv.com/video/3821838/index.html
Post hier nieuws, plaatjes van toen of nu, discussieer mee over een mogelijke nieuwe uitbarsting of die van toen. Alle inbreng is welkom
[ Bericht 2% gewijzigd door Frutsel op 01-01-2007 20:38:02 ]
Moooiii
Hoe heet zo'n wolk ook al weer?
quote:LenticularisOp maandag 1 januari 2007 21:00 schreef -skippybal- het volgende:
[afbeelding]
Moooiii
Hoe heet zo'n wolk ook al weer?
quote:Hele maffe foto.Op maandag 1 januari 2007 21:00 schreef -skippybal- het volgende:
[afbeelding]
Moooiii
Hoe heet zo'n wolk ook al weer?
quote:Klopt! Die heb ik zelf ook gezien. Er is ook een film gemaakt in 1981 dacht ik over St.HelensOp dinsdag 2 januari 2007 11:44 schreef X. het volgende:
Er is ook een docu van National Geographic van
quote:Overigens ging die NG over de ramp en niet echt over de berg zelf, maar het was wel fascinerend om te zienOp dinsdag 2 januari 2007 11:47 schreef Frutsel het volgende:
[..]
Klopt! Die heb ik zelf ook gezien. Er is ook een film gemaakt in 1981 dacht ik over St.Helens
quote:Voor de mensen die het niet gezien hebben: http://www.ngc.tv/watch/program_details.aspx?id_program=4514
A thermal-infrared image of Mount St. Helens' lava dome taken Jan. 23 reveals multiple 'hot spots.'
While the two volcanoes are different in many respects, Mount St. Helens appears to have become an "open system" as its domebuilding eruption that began in the fall of 2004 continues at a pace that has been unchanged for the past year, said Daniel Dzurisin, a geologist at the U.S. Geological Survey's Cascades Volcano Observatory.
Analyzing of digital elevation models made from high-resolution aerial photographs, scientists have kept close tabs on the rate at which lava has been pushing into the crater.
At first it was about a dumptruck load, roughly 8 cubic yards, per second.
A year later it was down to slightly more than 1 cubic yard per second, and since last April it has been fairly constant about 0.6 of a cubic yard per second — still the equivalent of about nine truckloads every two minutes.
The longer the eruption continues at that rate, the more likely it is that a direct pathway has developed for molten rock to emerge from deep within the planet's crust, Dzurisin said, adding that it will take another year of data to reach a more definite conclusion.
"That situation could go on for a long time," Dzurisin said. "The ongoing eruption (at Kilauea) in Hawaii, for example, started in 1983."
Other evidence indicating the development of an open system at St. Helens is the slowing of deformation around the flanks of the volcano, indicating the magma chamber beneath the surface is being refilled rather than deflating, which would cause sagging.
At Johnston Ridge Observatory, five miles north of the crater, a global positioning system monitor has moved toward the volcano by about an inch since the eruption began, with most of the movement coming in the first year and a half.
Since then the rate of deformation has subsided considerably while lava continues to emerge, indicating the magma is being replenished.
It took about four centuries to build the symmetrical, cone-shaped peak that led St. Helens to be compared with Mount Fujiyama in Japan before a massive blast on May 18, 1980, removed the top 1,314 feet, flattened miles of southwest Washington forests and left 57 people dead.
"We know that St. Helens is capable of dome eruptions lasting decades," Dzurisin said.
Echt een aanrader om te bezoeken als je in de buurt bent.
Ik heb trouwens een foto die enkele dagen voor de uitbarsting vanuit een vliegtuig is genomen door een kennis van me, zal deze binnenkort eens opzoeken.
deze maand alweer dertig jaar geleden
quote:Earthquake swarm rattles area near Mt St.Helens
MOUNT ST. HELENS, Wash. – A series of nine small earthquakes shook an area near Mount St. Helens over the weekend.
Seismologists at the University of Washington have been monitoring the quakes.
A 2.6 quake occurred at 2:26 p.m. on Saturday about six miles north of the volcano. Another quake, a 2.5, occurred at 2:44 p.m. in the same area. The depth for both quakes was two miles. Another quake occurred six miles north-northwest at 10:48 p.m. That measured 2.2 and was 2.2 miles deep.
Smaller quakes, ranging from magnitude 1.3 to 2.2, occurred on Sunday.
"It's something we're watching but we're not alarmed," said Bill Steele, Seismology Lab Coordinator for the Pacific Northwest Seismograph Network.
Steele said St. Helens while is an active volcano, it's also sitting on an area of tectonic weakness.
"It's kind of an interesting swarm but it's since quieted down," said Steele.
quote:What do the quakes near St.Helens mean?
SEATTLE - The Seismology Lab at the University of Washington keeps close tabs on anything that shakes around Mt. St. Helens.
Lately, the area just north of the crater, left over from the explosive 1980 eruption, has been shaking again. It always gets the attention of scientists.
"That is why we keep actually looking at the seismicity so carefully, so we can pick up any sign of unrest," said Silvio De Angelis, a volcano seismologist. He has studied quakes at other volcanoes around the world, as well as in the Cascades.
The current swarm now totals between 30 and 35 quakes over the last few days. Some are so tiny they barely register on seismographs. The biggest came on Sunday the 30th, with a magnitude of 2.6, strong enough to be felt by somebody close by. The quakes are about two miles deep.
The main swarm is happening five miles north of the crater, putting it under Johnston Ridge, site of an observatory where most tourists and visitors can view into the open side of the crater.
Some other small quakes, including a handful today, are happening under the crater itself, but don't concern scientists.
They've seen swarms in this area before.
In September 2004, quakes under the mountain grew from a few to thousands in a matter of days as magma made its way up to the surface. Scientists both at the Cascades Volcano Observatory and at the Pacific Northwest Seismic Network at UW don't think that is what's happening now.
These quakes are "tectonic," meaning they show signs of being typical of earthquakes involving shifting fault lines, not a sign of the ground being distorted by the underground forces of volcanoes.
But a swarm of quakes is always worth paying close attention to.
"This is why we are always on alert, and when there's a swarm of earthquakes like these, we always have our pagers with us," said De Angelis.
St. Helens is de laatste tijd wel vaak onrustig... hoop dat die niet nog een keer ontploft. Maar als er dan toch iets kapot moet in die regio, liever St. Helens dan Mount Rainier.
Wat is er met Mt. Rainier?quote:Op dinsdag 1 februari 2011 13:04 schreef Fogel het volgende:
Mhh, die foto heb ik niet meer kunnen vinden.
St. Helens is de laatste tijd wel vaak onrustig... hoop dat die niet nog een keer ontploft. Maar als er dan toch iets kapot moet in die regio, liever St. Helens dan Mount Rainier.
De tien gevaarlijkste vulkanen van de VS
Ligt dichtbij Seattle en een lavastroom zou hoogstwaarschijnlijk precies door de stad heen gaan. Niet handig.quote:
Gisteren is er een aardbeving van 4.3 op de schaal van Richter gemeten in de buurt van Mount St. Helens in de staat Washington. Het is de zwaarste beving sinds 1981. De beving werd gevoeld 192 kilometer ten noorden en zuiden van het epicentrum, de beving werd geregistreerd om 10:35 uur (lokale tijd) en was gecentreerd rond 8.8 kilometer ten noorden van de Mount St. Helens krater, op een diepte ongeveer 4.8 kilometer.
Er deden zich ook drie naschokken voor, die lagen tussen de 2.0 en de 3.0 op de schaal van Richter. Naast die naschokken zijn er ook nog meer dan 100 kleinere naschokken geweest. De beving is waarschijnlijk opgemerkt door duizenden mensen, maar slechts 870 mensen deden er melding van. Bezoekers die op dat moment aanwezig waren bij het Mount St. Helens monument, dat ongeveer 64 kilometer van het epicentrum af ligt voelde de grond bewegen.
Hoewel de uitbarsting van 1980 ook vooraf ging met een aardbeving van 5.2 en naschokken van vergelijkbare sterkte lijkt het er niet op dat deze beving veroorzaakt is door veranderingen van de vulkaan, sinds 2008 zijn er geen grote vulkanische activiteiten meer ontdekt. Mount St Helens, is een vulkaan in Skamania County, Washington VS, vooral bekend vanwege de verwoestende uitbarsting in 1980, waarbij tientallen mensen omkwamen en een groot deel van de berg instortte.
©onweer-online
quote:Volcano sends love wave
Call it a Valentine’s Day tradition on a monumental scale.
A 4.3-magnitude earthquake occurred 6 miles north of Mount St. Helens on Monday morning — exactly 30 years to the day after an even bigger earthquake occurred at nearly the exact same spot. Monday’s quake was followed by more than a half-dozen much smaller aftershocks, all in the same general area.
Scientists said the seismic activity does not indicate magma rising at Mount St. Helens. They’ve detected none of the shallow quakes or gas typically associated with an imminent volcanic eruption.
But they said Monday’s quake — just like the one 30 years ago — is at least indirectly related to the volcano.
Felt as far away as south Puget Sound and Astoria, Ore., Monday’s first temblor was the biggest in the Pacific Northwest in two years. Scientists suspect the quake, at 10:35 a.m., may have occurred in a bit of post-eruption settling in the landscape surrounding Mount St. Helens, which last erupted between 2004 and 2008.
The quake generated a specific kind of shear wave felt over a wide area, said Bill Steele, seismology lab coordinator at the University of Washington in Seattle.
In a curious twist of timing and fate, this type of surface wave is named for the scientist who discovered it: early 20th-century British geophysicist Augustus Love.
“It was very rich in Love waves,” Steele said, with scant trace of irony. “Those Love waves coming out were probably what people were feeling.”
If so, it’s not the first Valentine’s Day that the volcano has been massaged by waves of Love.
Post-eruptive settling likely triggered a 5.5-magnitude quake in the vicinity of Johnston Ridge on Feb. 14, 1981, according to seismologists in Vancouver and Seattle. They said the massive and sudden expulsion of magma during the catastrophic eruption of May 18, 1980, probably increased stress in a well-documented seismic zone that runs north-to-south underneath Mount St. Helens.
In effect, the earth shifted nine months after the eruption.
“That was a fairly significant adjustment,” said Seth Moran, a seismologist with the U.S. Geological Survey in Vancouver. “You had a cubic kilometer of material removed from depth.”
The earthquake and aftershocks on Monday were not as large as the ones in 1981.
However, Moran said the location and depth — roughly 3 miles below the Johnston Ridge Observatory — bears striking similarities to the 1981 temblor. The volcano spurted a new lava dome between 2004 and 2008, which may have created new strain in the seismic zone below Johnston Ridge.
Seismometers detected a swarm of smaller earthquakes in the general area about three weeks ago.
“We’re about three years removed from the end of the last eruption, in January of 2008,” Moran said. “Perhaps these earthquakes are in response to the end of that eruption.”
In that case, it may be well to keep this in mind for some future Valentine’s Day excursion to Mount St. Helens: If this hill’s a rockin’, don’t come a-knockin’.
“One can’t rule these things out completely,” Steele said.
Maar hij moet niet gaan ontploffen natuurlijk.
quote:MAP 2.2 2011/02/15 05:09:32 46.279 -122.218 4.7 9 km ( 6 mi) NNW of Mount St. Helens Volcano, WA
MAP 1.1 2011/02/15 02:19:29 46.279 -122.212 3.6 9 km ( 6 mi) NNW of Mount St. Helens Volcano, WA
MAP 1.0 2011/02/15 00:53:39 46.280 -122.214 3.1 9 km ( 6 mi) NNW of Mount St. Helens Volcano, WA
MAP 2.3 2011/02/14 20:21:42 46.278 -122.216 4.7 9 km ( 6 mi) NNW of Mount St. Helens Volcano, WA
MAP 1.1 2011/02/14 19:54:51 46.274 -122.215 2.8 9 km ( 5 mi) NNW of Mount St. Helens Volcano, WA
MAP 2.3 2011/02/14 19:35:08 46.285 -122.216 5.4 10 km ( 6 mi) NNW of Mount St. Helens Volcano, WA
MAP 1.1 2011/02/14 19:12:06 46.276 -122.211 3.8 9 km ( 5 mi) NNW of Mount St. Helens Volcano, WA
MAP 1.3 2011/02/14 19:01:25 46.279 -122.212 4.9 9 km ( 6 mi) NNW of Mount St. Helens Volcano, WA
MAP 1.3 2011/02/14 18:54:06 46.285 -122.213 6.0 10 km ( 6 mi) NNW of Mount St. Helens Volcano, WA
MAP 1.2 2011/02/14 18:47:55 46.279 -122.208 4.6 9 km ( 6 mi) NNW of Mount St. Helens Volcano, WA
MAP 2.8 2011/02/14 18:37:45 46.280 -122.209 4.5 9 km ( 6 mi) NNW of Mount St. Helens Volcano, WA
MAP 4.3 2011/02/14 18:35:25 46.282 -122.212 5.5 9 km ( 6 mi) NNW of Mount St. Helens Volcano, WA
quote:USGS watching St.Helens closely
The United States Geological Survey is watching the Mount St. Helen's volcano closely after a series of earthquakes struck on Monday. The area around Mount St. Helen's in Washington state has been experiencing minor earthquakes since an initial quake measuring 4.3 in magnitude struck around 10:35 a.m. local time, according to the USGS. Since that first quake, several smaller aftershocks were registered ranging between 1.0 and 2.8 in magnitude.
All of these earthquakes were centered in an area approximately five to six miles north of the Mount St. Helen's crater near the Johnston Ridge Observatory. The quakes were registered at depths between 1.7 and 3.7 miles. In total, at least 12 small earthquakes were registered in the area since the first quake on Monday.
This series of small earthquakes occurring in approximately the same location over a short period of time is known as an earthquake swarm. According to the Global Volcanic Earthquake Swarm Database earthquake swarms are especially common around volcanoes and are often reliable methods of predicting an eruption but the Alaska Volcano Observatory website offered that there may be no need for alarm. The AVO website explained that while earthquake swarms may offer information that a volcano is becoming restless, they are not necessarily indicators of a pending eruption. According to the AVO, "Most seismic swarms are not precursors to eruptions."
The AVO website states that a great deal of seismic data from satellite imagery, deformation, gas measurements and the history of the volcano's geologic past are all taken into consideration when determining an eruption risk.
According to the USGS, seismic activity is common around volcanoes as volcanoes can produce various types of earthquakes--tectonic-type or volcanic-type. Tectonic-type earthquakes around a volcano occur when rocks break along faults or fractures around the volcano. Seismologists must determine if an earthquake near a volcano is tectonic or volcanic as the differences are very subtle.
Earthquakes are different from volcanic tremors, which are vibrations that last longer in duration (lasting from minutes up to days) and are caused by magma movement, movement of pressurized fluids or the escape of pressurized steam or gas.
According to the USGS, the most recent earthquakes are in the same location as another small swarm that happened in late January. In addition, the most recent swarm of quakes is similar to a swarm that began in August 1980. That swarm culminated in a 5.5 magnitude earthquake in February 1981.
The USGS website stated that studies conducted after the 1980 eruption of Mount St. Helen's "suggested that the magma removed during the May 1980 eruption and subsequent lava-dome building caused faults along the seismic zone to slip in response to the magma withdrawal. Similar interaction of volcanic activity and tectonic fault movement is possible in the case of" recent earthquakes,
The USGS also stated that "at present there appears to be no signs of unrest in the volcanic system" and that "The USGS and the Pacific Northwest Seismic Network at University of Washington continue to watch conditions at Mount St. Helens closely."
The current volcano alert level for Mount St. Helen's is still set at normal.
Scientists look for clues when St.Helens blows again
Mount St. Helens has been mostly quiet since its most recent dome-building eruptions ended in January 2008. But scientists say it’s a sure thing the volatile volcano in our backyard will reawaken.
The question they hope to answer is when.
Clues to the volcano’s future lie in the faint signals of magma moving in a cigar-shaped chamber deep within the mountain, in the eruptive history of a similar volcano on Russia’s remote Kamchatka Peninsula, and in the long geological record contained within Mount St. Helens itself.
Cynthia Gardner, a scientist at the U.S. Geological Survey’s Cascades Volcano Observatory in Vancouver, predicts the mountain will resume rebuilding itself sooner rather than later.
“Mount St. Helens will probably erupt again within the next several decades,” she says. “As we look at its eruptive history, we know there was a flank collapse 2,500 years ago. We saw the cone rebuild itself over a century or a century and a half.”
Yet since the 1980 eruption, she said, the mountain has rebuilt only 7 percent of its pre-eruption mass. “If we look at patterns from St. Helens’ past history, and from volcanoes around the world, we come to the conclusion we are likely to see more eruptions.”
Mapping the mountain
Michael Clynne, a USGS scientist based in Menlo Park, Calif., has studied Mount St. Helens up close since 1997. He’s making a geological map of the area and visits the volcano every summer, climbing to the crater rim, camping out on the mountain’s flanks, walking around on its deposits, and collecting rocks.
Back in his lab, the rocks are sliced thin, studied under powerful microscopes and dated using radiocarbon dating or, for rocks older than 20,000 years, argon dating. They hold a record of volcanic activity stretching back thousands of years.
The rock specimens document that the explosive 1980 eruption, triggered by an earthquake and the largest volcanic landslide in history, was part of a cycle that has repeated itself over millennia. The pyroclastic flows of superheated gases, the debris flows and the ash deposits that instantly transformed the landscape were nothing new. In fact, the serene symmetrical peak that blew its top in 1980 is the product of a long, violent history — a history that is still being written.
“Twenty-two hundred years ago, there was a much bigger collapse on the south side of the mountain that dammed the Lewis River,” Clynne said. “Most of those deposits lie beneath Lewis River reservoirs now, but you can see the evidence around the reservoirs, in breakout lahars.”
Spirit Lake, displaced by the collapse of the north flank of the mountain in 1980, was created by the damming of the North Fork of the Toutle River about 3,900 years ago, Clynne said.
“There were big eruptions that blocked the Toutle River in the earliest part of the Spirit Lake stage” he said. “The lake has been created and destroyed several times. There have been big floods down the Toutle River several times in the past thousands of years, caused by the breaching of temporary lakes.”
Two big floods that occurred in the Pine Creek period, some 2,900 to 2,550 years ago, “may have been precipitated by the collapse of lava domes,” he said.
Based on his research to date, Clynne doesn’t expect another explosive eruption like the one in 1980 anytime soon.
“That eruption was caused by an accumulation of gas-rich magma,” he said. “That magma takes decades to centuries to accumulate, so typically, the mountain cannot have another of these eruptions in the near future. What happens next is that there is lots of magma left in the chamber, but it’s gas-poor. You get dome eruptions for decades to centuries.”
From late 1980 to 1986, Mount St. Helens spewed lava sporadically, building a lava dome that grew to a height of about 1,000 feet and a width of 3,500 feet. That was followed by a period of quiescence that lasted until 2004, when dome-building resumed.
The rock that emerged from the magma chamber during the 2004-08 period was composed of high-silica, gas-poor andesite and dacite.
“The lava comes out of the ground almost solid,” Clynne said. “It is not able to flow. It piles up right over the vent, then sort of falls over. It will do this again with gas-poor magma over the next few decades, until it gets a new load of gas-rich magma.”
“We have no way of knowing when the next batch of dacite will emerge,” he said. “When enough of it melts to separate, to become buoyant, it will come up the conduit to the shallow chamber.” That chamber lies five to six kilometers beneath the mountain and measures about one kilometer across.
“When you get enough gas-rich magma at the top, that’s when it erupts.”
In Clynne’s geological map, the entire edifice of the volcano and its flanks will be portrayed — a profile of Mount St. Helens through time.
The truncated mountain “will become a peak again,” Clynne said. “We can’t really say if it will be beautiful and symmetrical again. It depends on the kinds of eruptions and where the vents are. If it continues to build the way it is now, it will eventually fill the crater and reshape itself. That requires that we don’t have another collapse.”
Listening for magma
Tracking that flow of magma is a challenge, says Mike Lisowski, a geophysicist at the Cascades Volcano Observatory. With the help of sophisticated sensors, he studies the deformation of the mountain, looking for signals that magma is recharging within the volcano.
Mount St. Helens is one of two Cascade volcanoes being closely monitored by the Plate Boundary Observatory, a National Science Foundation-funded research project that studies movement between the Pacific and North American tectonic plates. (The other peak is Mt. Shasta in northern California.)
The program has installed 30 GPS units on Mount St. Helens and out to a distance of 20 miles from the mountain. Tiltmeters on the flanks of the mountain also detect changes in its shape, known as deformation.
“It’s a pity that the Plate Boundary Observatory instruments weren’t put in earlier,” Lisowski said. “It would have been great to have had them in 2004.”
So far, deformation of the mountain due to the movement of magma is “barely perceptible,” Lisowski said.
“During the whole eruption period from 2004 to 2008, the site at Johnston Ridge Observatory moved toward the mountain by just one inch,” he said.
Yet there is movement of various types.
“When we look at sites all around the mountain, we see that they are all moving toward the mountain,” Lisowski said. “Also, there is a downward motion that indicates that somewhere deep inside the volcano, magma is being withdrawn. It’s deflation, like with a balloon. The walls of the balloon get smaller. The crust surrounds the balloon.”
Other things are going on beneath the mountain, as well.
“There’s background tectonic movement,” Lisowski said. “Everything is moving to the north-northeast.” Slow-motion underground earthquakes known as “slip events” occur when the Pacific plate slips beneath the North American plate.
“They aren’t releasing tremors, but they do cause movement,” Lisowski said. That makes it hard to detect deformation of the mountain itself. “We are looking for small volcanic signals in a background of tectonic events.”
A Russian ‘sister’
For a few years, geologists thought a remote Russian volcano called Bezymianny might hold the answer to the future of Mount St. Helens. The 9,453-foot peak erupted in a massive blast in 1956 that had a lot in common with Mount St. Helens. Bezymianny never stopped erupting during the following 50 years. By 2007, its lava dome covered most of the crater surface and poked well above the crater rim.
Both mountains are stratovolcanoes — mountains that build themselves with a series of eruptions spewing lava, ash, cinders and blocks.
The first sign that Mount St. Helens was reawakening in the fall of 2004 was the emergence of fire-red lava from within the crater. A week and a half later, on Oct. 1, the volcano shot a noontime blast of steam and ash into the sky. A new dome-building stage had begun.
Scientists looked to Bezymianny for clues to what might be next.
They calculated that the Russian volcano’s 50-year-old lava dome was at least 10 times the size of the 111 million cubic yards of material that piled up in the crater of St. Helens between 2004 and 2006.
John Pallister, a USGS geologist at the CVO, even speculated that the two mountains were “sister volcanoes,” and that if the eruption at Mount St. Helens were to continue indefinitely, in a few decades it would look a lot like Bezymianny.
That hasn’t happened. Dome-building activity at St. Helens stopped in 2008. The mountain did rumble to life briefly three months ago, on Valentine’s Day, with a 4.3-magnitude earthquake north of the peak, followed by more than a half-dozen smaller aftershocks.
But scientists said the seismic activity did not indicate that magma was rising within the volcano. Instead, they speculated that it might be a sign of post-eruption settling in the landscape surrounding the mountain.
Assumptions shaken
Research into the history of the volcano has shattered old assumptions, Clynne said.
“We used to think the volcano began 45,000 years ago. We started dating rock and found it really began 250,000 years ago.”
Mount St. Helens is by far the world’s most-studied volcano. That’s among its most important legacies, Clynne said.
“Mount St. Helens has renewed interest in volcanology all over the world.”
quote:Mount St. Helens ‘recharging’ amid increase in earthquake activity: USGS
PORTLAND, Ore. (KOIN) — Earthquake activity around Mount St. Helens spiked to nearly 350 quakes between February 1, 2024, and June 18, 2024, and officials say it may be a sign of “recharging” activity.
The increase in earthquake activity has only been small-magnitude quakes, but an increase nonetheless.
“Over the past several months, small magnitude earthquakes have been located at Mount St. Helens,” the Cascades Volcano Observatory said. “The seismicity is similar to what was observed at this volcano from July to December 2023. No significant changes have been observed in other monitoring parameters and there is no change in alert levels at this time. Mount St. Helens remains at normal, background levels of activity.”
USGS seismicity increase around Mount St. Helens (courtesy USGS)
According to an X post from the USGS Volcanoes, the seismic activity seen recently could mean the arrival of additional magma known as a process called “recharge.”
“Small magnitude earthquakes located beneath Mount St. Helens at depths well below sea level are generally thought to be associated with pressurization of the magma transport system. One cause for this pressurization is the arrival of additional magma, a process called recharge.”
The Cascades Volcano Observatory went on to explain that “magma slowly rises through the lower crust and accumulates in a reservoir about 2.5 to 6 miles (4‒10 km) below sea level. Recharge events can occur when magma enters this upper reservoir and increases stresses that lead to earthquakes.”
The USGS Cascades Volcano Observatory says they will continue to monitor this activity and will provide any updates or warnings if warranted.
May marked 44 years since Mount St. Helens erupted, sending ash and debris across the Pacific Northwest. Fifty-seven people were killed in what is considered the deadliest volcanic eruption in the U.S.
Experts frequently note that earthquakes are simply part of what Mount St. Helens does. As Dr. Scott Burns, professor emeritus of engineering geology at Portland State University previously told Nexstar’s KOIN, Mount St. Helens has gone through “periods of coming back to life and then no activity, back to life and no activity” since its May 1980 eruption.
Burns, too, noted that magma is coming into Mount St. Helens’ crater in order to form the dome.
According to the USGS, Mount St. Helens is the second-most hazardous volcano in the U.S. behind Hawaii’s Kīlauea, which last erupted earlier this month.