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Mount St Helens -uitbarsting

Mount St Helens -uitbarsting

Mount St Helens -uitbarsting


Amerikaanse geskiedenis

Op 18 Mei 1980 het 'n vulkaan in die staat Washington met die naam Mount St. Helens uitgebars. Dit was die grootste vulkaniese uitbarsting in die kontinentale Verenigde State sedert 1915. 'n Reuse aspluim het uit die uitbarsting opgestaan ​​en 'n groot deel van die ooste van Washington verdonker en versprei oor 'n groot deel van die Verenigde State en Kanada.

Waar is Mount St. Helens?

Mount St. Helens is in die suidweste van die staat Washington ongeveer 90 kilometer suid van Seattle geleë. Dit is deel van die Cascade -bergreeks. Die Cascade -bergreeks is deel van 'n groter geologiese kenmerk genaamd die Ring of Fire. The Ring of Fire omring die Stille Oseaan en bestaan ​​uit honderde vulkane.

Het hulle geweet dit gaan uitbars?

Geoloë het 'n goeie idee gehad dat die vulkaan gaan uitbars. Hulle het egter nie presies geweet wanneer nie. Die eerste teken was 'n toename in aardbewingaktiwiteite in Maart 1980. Gedurende Maart en April het die berg meer aktief geword, waaronder verskeie stoomuitbarstings. In April verskyn 'n groot bult aan die noordekant van die vulkaan. Op hierdie stadium het geoloë geweet dat die uitbarsting waarskynlik binnekort sou plaasvind.


Die vulkaan breek uit
deur Mike Doukas vir die USGS

The North Face stort in duie

Op 18 Mei het 'n groot aardbewing van 5,1 die gebied geruk. Dit het veroorsaak dat die noordkant van die berg in duie gestort het. Die meerderheid van die noordelike kant van die berg het in 'n reuse -grondverskuiwing verander. Dit was die grootste grondverskuiwing in die geskiedenis. Die reuse massa aarde het teen 'n spoed van meer as 100 myl per uur gegly en alles in sy pad uitgewis. Die grondstorting het Spirit Lake langs die berg getref en het 600 voet golwe veroorsaak.

'N Paar sekondes na die grondstorting, ontplof die noordekant van die berg in 'n reuse -uitbarsting. 'N Laterale ontploffing het gasse en puin met meer as 300 honderd kilometer per uur uit die kant van die berg oorverhitte gasse en puin geskiet. Die ontploffing het gebrand en alles in sy pad weggeblaas. Ongeveer 230 vierkante kilometer bos is vernietig.

'N Reuse pluim vulkaniese as het ook in die lug bo die berg gevorm. Die pluim het die vorm aanneem van 'n sampioenwolk wat ongeveer 80 000 voet in die lug gestyg het. Die vulkaan het die volgende nege uur aanhou as uitspoeg. 'N Groot deel van die ooste van Washington is in die duisternis gedompel toe die as versprei het.

Hoeveel skade het dit aangerig?

Die Mount St. Helens -uitbarsting van 18 Mei 1980 was die ekonomies mees vernietigende vulkaniese uitbarsting in die geskiedenis van die Verenigde State wat meer as $ 1 miljard se skade aangerig het. Ongeveer 200 huise is vernietig en 57 mense is dood deur die ontploffing. Paaie, brûe en spoorweë vir 'n paar kilometer om die berg is ook vernietig. Ash het 'n groot deel van die ooste van Washington beslaan. Lughawens moes gesluit word en mense moes uit groot hope as grawe. Na raming moes ongeveer 900 000 ton as van paaie en lughawens verwyder word.

Die vulkaan het gedurende 1980 nog 'n paar keer uitgebars en daarna bedaar. Daar was klein uitbarstings tot 1986 toe die berg stil word. In 2004 het Mount St. Helens weer aktief geword en was aktief met klein uitbarstings tot en met 2008.


Die uitbarsting van Mount St. Helens: die onvertelde geskiedenis van hierdie rampspoedige gebeurtenis

Robin Lindley is 'n skrywer en prokureur in Seattle, en die funksie-redakteur van die History News Network (hnn.us). Sy artikels het verskyn in HNN, Crosscut, Salon, Real Change, Documentary, Writer's Chronicle en ander. Hy het 'n spesiale belangstelling in die geskiedenis van konflik en menseregte. U kan sy ander onderhoude hier vind. Sy e -pos: [email protected]

As u meer as 40 jaar oud is en in 1980 in die staat Washington gewoon het, het u waarskynlik 'n storie oor die uitbarsting van Mount St. Helens.

Op Saterdag 17 Mei 1980 is ek en my vrou Betsy op 'n helder, warm dag in Spokane, Washington, getroud. Die volgende oggend, onbewus van enige nuus, sien ons 'n donker oewer van wat ons gedink het donderwolke uit die suidweste na Spokane kom.

Dit het geblyk dat die inkwolke vulkaniese as uit die uitbarsting van Mount St. Helens, meer as 250 myl daarvandaan, gedra het. Teen die middag was die Spokane -lug donker soos die nag en 'n bestendige reënbui van die poeieragtige as het die son deur die dag verduister.

Baie van ons huweliksgaste was die Sondag in die verblindende asstorm vasgevang toe hulle weswaarts na Seattle ry. Verskeie het daagliks in motels of noodskuilings in kerke of skole vasgekeer en soms langer.

Ons vriende het uiteindelik ongeskonde by die huis aangekom, maar dit was nie vir almal die geval nie. Die massiewe vulkaniese ontploffing vanaf Mount St. Helens het 57 mense dood gelaat, as op agt Amerikaanse state en vyf Kanadese provinsies gestort en meer as 'n miljard dollar se skade aangerig.

Die bekroonde skrywer Steve Olson verweef behendig die geskiedenis en wetenskap van hierdie rampspoedige gebeurtenis in sy baanbrekende nuwe boek Uitbarsting: die onvertelde verhaal van Mount St. Helens (Norton). Gebaseer op uitputtende navorsing, vertel sy boek nie net die uitbarsting en sy tol nie, maar kyk hy ook terug na ekonomiese en politieke ontwikkelinge wat die lot van diegene naby die berg bepaal het toe dit waai, veral die gesellige verhouding tussen die kragtige Weyerhaeuser -hout maatskappy en 'n paar regeringsliggame.

Olson se boek is 'n ondersoekwerk sowel as 'n lewendige storievertelling wat lesers uit die wêreld van houtkap en spoorwegbaronne meer as 'n eeu gelede na die lewens van wetenskaplikes, houtkappers, regeringsamptenare en vele ander neem ten tyde van die uitbarsting. Sy boek demonstreer hoe die geskiedenis 'n konstante teenwoordigheid in ons lewens is, terwyl hy noodlottige besluite wat die uitbarsting voorafgegaan het, belig en deel in evokatiewe prosa die voorheen onvertelde verhale van diegene wat omgekom het sowel as diegene wat hierdie massiewe vulkaniese ontploffing oorleef het. Olson beskryf ook die nagevolge van die uitbarsting: die veerkragtigheid van die natuur, wetenskaplike vooruitgang, beleidsveranderinge en die skepping van 'n nasionale gedenkwaardigheid - en hy deel idees oor paraatheid vir die komende natuurrampe.

Olson is 'n wetenskaplike skrywer in Seattle. Sy ander boeke sluit in Mapping Human History: Genes, Race, and Our Common Origins, 'n finalis vir die National Book Award en ontvanger van die Science-in-Society-toekenning van die National Association of Science Writers Count Down: Six Kids Vie for Glory at die World's Toughest Math Competition (Boston: Houghton Mifflin), aangewys as die beste wetenskapboek van 2004 deur die tydskrif Discover en saam met Greg Graffin, Anarchy Evolution. Sy artikels het verskyn in The Atlantic Monthly, Science, Smithsonian, The Washington Post, Scientific American en vele ander tydskrifte. Olson het ook gedien as konsultantskrywer vir die National Academy of Sciences en National Research Council, die Withuis se kantoor vir wetenskap en tegnologiebeleid, die President's Council of Advisors on Science and Technology, die National Institutes of Health en vele ander organisasies.

Mnr. Olson het mildelik per e -pos gereageer op 'n reeks vrae oor sy nuwe boek oor Mount St. Helens.

Robin Lindley: U is 'n bekwame skrywer Steve, en u het oor 'n wye verskeidenheid wetenskaponderwerpe geskryf. Wat het jou geïnspireer om navorsing te doen en te skryf oor die uitbarsting van Mount St. Helens in Mei 1980?

Steve Olson: Ek het grootgeword hier in die noordweste van die Stille Oseaan, in 'n klein boerderydorpie ongeveer 100 myl teen die berg St. Helens, maar ek het in die 1970's oos gegaan vir 'n universiteit en daar gebly nadat ek my toekomstige vrou agter in 'n Engelse klas ontmoet het ( alhoewel ek 'n fisika -hoofvak was, het ek eers later belang gestel in skryf). In 2009 het sy werk gekry in Seattle, so ons het teruggekeer na my geboortestaat. Ek het verskeie vorige handelsboeke oor meestal wetenskaplike onderwerpe geskryf, maar toe ons hier kom, besluit ek om 'n boek te skryf oor die mees dramatiese ding wat ooit in Washington gebeur het - en die uitbarsting van Mount St. Helens was die voor die hand liggende keuse.

Robin Lindley: Waar was jy toe die berg uitgebars het? Het u enige mense geken wat deur die uitbarsting geraak is?

Steve Olson: Op 18 Mei 1980 woon ek buite Washington, DC, werk ek as vryskutskrywer en redakteur vir wetenskap- en tegnologiebeleid en was drie weke weg van trou. My ouma, wat nog in die klein dorpie waar ek grootgeword het, gebring het, het 'n fles as gebring wat sy van haar oprit na die troue as 'n gesprek begin het.

Robin Lindley: Daar is baie oor die uitbarsting geskryf, maar u het deeglike navorsing gedoen om die geskiedenis van die berg en die ontploffing daarvan te besoek. Wat was u navorsingsproses en hoe het die boek ontwikkel sedert u daaraan begin werk het tot die publikasie daarvan?

Steve Olson: Baie vorige boeke is oor Mount St. Helens geskryf, maar toe ek navorsing oor die boek begin doen, het ek ontdek dat daar nog nooit oor baie dele van die verhaal geskryf is nie. Ek het veral belanggestel in die 57 mense wat deur die uitbarsting dood is. Waarom was hulle so naby aan so 'n gevaarlike vulkaan - net drie kilometer van die kruin af?

Dit het geblyk dat die gevaarsones veel te naby aan die berg was, wat langs die grens loop tussen grond wat in besit is van die Weyerhaeuser -houtmaatskappy in die weste en die Gifford Pinchot National Forest in die ooste. Ek het besluit dat ek moet vertel hoekom die grens daar is en nie elders nie, en dat ek die verhale van Weyerhaeuser en grondgebruik in die westelike Verenigde State moet vertel.

Robin Lindley: U het die historiese konteks van die uitbarsting in 1980 uiteengesit, en die Noordwes was 'n heel ander plek as nou, 36 jaar later. Wat is die min dinge wat u wil hê dat lesers in daardie tyd moet verstaan?

Steve Olson: Toe ek die Stille Oseaan Noordwes in 1974 verlaat, was daar min om 'n ambisieuse persoon wat nuuskierig was oor die wêreld hier te behou. Weyerhaeuser en Boeing was die twee groot ondernemings in die staat. Die ekonomie het gestagneer, die kultuur was eienaardig en geïsoleer, en die res van die Verenigde State het ver gelyk. Dit het alles in die tagtigerjare begin verander, en die Noordweste is nou heeltemal anders as toe ek grootgeword het - behalwe natuurlik die diepgaande natuurskoon wat ons van alle kante omring.

Robin Lindley: Hoe vergelyk die geweld van die uitbarsting van Mount St. Helens met ander vulkaniese uitbarstings?

Steve Olson: In 'n globale en geologiese konteks was die uitbarsting van Mount St. Helens in 1980 nie besonder groot nie.

Terwyl ek in die boek skryf, het die afgelope 500 jaar meer as 20 groter uitbarstings regoor die wêreld plaasgevind. Mount St. Helens het in die verlede baie groter uitbarstings gehad. Toe Mount Mazama ongeveer 7 000 jaar gelede in Oregon uitbars, het dit 100 keer soveel as vrygelaat as wat Mount St. Helens in 1980 gedoen het voordat dit ineengestort het tot die huidige Crater Lake. Dit gesê, die stortvloed wat die noordelike flank van Mount St. Helens in 1980 vernietig het, was die grootste in die geskiedenis van die mens (dus die afgelope paar duisend jaar), en die ontploffing wat 230 vierkante myl bos verwoes en 57 lewens geneem het, was grootliks onverwags deur geoloë, so dit was 'n groot gebeurtenis.

Robin Lindley: Hoe is die berg en sy omgewing verander deur die uitbarsting? Wat was die gebied wat vernietig is deur die vulkaan, flora en fauna wat verlore geraak het, en die hoeveelheid as wat na die ooste gestrooi is?

Steve Olson: Die uitbarsting in 1980 het ongeveer 'n kubieke kilometer as uitgestraal, wat oor die Verenigde State van Washington na die staat New York geval het en uiteindelik regoor die wêreld gereis het op groot hoogtewinde. Benewens die mense wat doodgemaak is, het duisende diere in die omliggende woude gesterf, saam met byna al die plantlewe in die ontploffingsgebied, insluitend reuse ou groeibome wat al eeue lank gegroei het.

Robin Lindley: Die berg het in Maart en April 1980 gedreun en gebult. Het wetenskaplikes die laterale ontploffing in die noorde voorspel wat teen daardie tyd werklik plaasgevind het, of was hulle oortuig dat die berg die top en boontoe sou waai?

Steve Olson: Hulle het nie 'n laterale ontploffing in die noorde voorspel nie, maar hulle het geweet dat dit moontlik was. Mount St. Helens het voorheen na die kant toe geblaas, en hulle het geweet van ander vulkane wat dit gedoen het. Tog het die omvang van die ontploffing hulle verras. Vulkane in Rusland en in Japan het lateraal uitgebars, maar die grootte van die verwoeste gebied was nie so groot soos by die berg St. Helens nie. Toe Mount St. Helens egter so uitbars, het vulkanoloë in die verlede na afsettings deur ander vulkane gekyk en besef dat die uitbarsting in 1980 nie 'n geologies ongewone gebeurtenis was nie. Inteendeel, sommige vulkaniese lawines en laterale ontploffings was baie groter.

Robin Lindley: Jou boek dien as 'n huldeblyk aan die 57 mense wat tydens die uitbarsting verlore gegaan het. U het baie moeite gedoen om hul verhale uit onder meer argiewe en van vriende en familielede te versamel. Vir u, blyk dit, kan die wortels van hul afsterwe 'n eeu vroeër in die geskiedenis van houtkap en spoorweë rus? Hoekom is dit?

Steve Olson: Ek dink aan die 57 mense as slagoffers van die geskiedenis. Sommige van die geskiedenis was kort en persoonlik, wat verband hou met hul spesifieke omstandighede en besluite, maar ander dele van die geskiedenis wat by Mount St. Helens ter sprake gekom het, het dekades of eeue in die verlede gestrek.

Robin Lindley: Hoe het Weyerhaeuser groot houtvelde in die Cascades en op die Olimpiese Skiereiland verkry, en wat was die rol van spoorwegmagnaat James J. Hill?

Steve Olson: Vir my was dit die interessantste deel van die historiese verhaal. Soos ek gesê het, is die gevaarsone aan die westelike en noordwestelike kant van die berg langs die grens tussen Weyerhaeuser -land en die Gifford Pinchot National Forest getrek.

Hoe het Weyerhaeuser, 'n onderneming wat in die 19de eeu aan die oewer van die Mississippirivier gestig is, soveel grond in die suidwestelike deelstaat Washington besit? Dit is nie 'n oordrywing om te sê dat dit grootliks ontstaan ​​het nie, omdat Frederick Weyerhaeuser, die Duitse immigrant wat die onderneming begin het, die huis in 1891 langs Jim Hill in Summit Avenue in St. Paul, Minnesota, gekoop het.

Hill, wat die eienaar en dryfveer agter die Great Northern Railway van St. Paul na Seattle was, het onlangs beheer verkry oor die Northern Pacific Railroad, wat in 1870 gebou is, van Duluth na Tacoma. In die 1890's wou Hill die spoorlyn koop van Chicago na Burlington, Iowa (daarom word dit vandag die Burlington Northern Santa Fe -spoorweg genoem), en het geld daarvoor nodig gehad. Om die geld in te samel, verkoop hy 'n groot deel van die Noordelike Stille Oseaan se grondtoelaes in die staat Washington aan sy buurman Frederick Weyerhaeuser, wat besef het dat die woude van die Midde -Weste uitgeput is en nuwe houtbronne benodig. Dit is 'n ryk, ingewikkelde, ingewikkelde geskiedenis wat op 18 Mei 1980 direkte gevolge vir die mense rondom die berg gehad het.

Robin Lindley: Baie mense besef miskien nie dat hout op die berg toegelaat is nie. Wat het gebeur met die Weyerhaeuser -operasie daar ten tyde van die uitbarsting? Het bosboubelange wetenskaplikes en die Bosdiens oor veiligheid geïgnoreer?

Steve Olson: Weyerhaeuser het die land wes van Mount St. Helens vir die agt dekades voor 1980 hard aangeteken. Toe die berg in Maart, twee maande voor die groot uitbarsting, begin bewe, het die maatskappy sy grond bly aanteken, ondanks die gevare van naby werk die vulkaan. As die berg op 'n weeksdag eerder as 'n Sondagoggend uitgebars het, sou honderde Weyerhaeuser -houthakkers in die omliggende bosse gesterf het.

Robin Lindley: Wat was die rol van die staat Washington en goewerneur Dixy Lee Ray in die skep van gevaarsones by Mount St. Helens?

Steve Olson: Die staat wou nie inmeng met Weyerhaeuser se bedrywighede wes van die berg nie. Die maklike manier om dit te doen was om te verhoed dat die gevaarsones op Weyerhaeuser -eiendom getrek word. Die goewerneur van die staat Washington in 1980, Dixy Lee Ray, onderteken die bevel om die gevaarsones vas te stel in die wete dat dit te klein is. Maar die geoloë se voorspellings oor wat die berg sou doen, was onseker, en Ray was die soort persoon wat geglo het dat mense eenvoudig verstandig genoeg moet wees om alleen van die berg af weg te bly. (Alhoewel sy dit verskeie kere vanuit vliegtuie oor die hoof getoer het.)

Robin Lindley: U glo dat mense wat gesterf het en beseer is tydens die ontploffing 'n slegte rap gekry het as risiko's of spotters. Wat sou u wou hê dat lesers van hierdie mense moet weet?

Steve Olson: Na die uitbarsting het Dixy Lee Ray gesê dat die mense wat tydens die uitbarsting dood is, onwettig in die gevaarsones was, en Jimmy Carter, wat 'n paar dae na die uitbarsting oor die ontploffingsgebied gevlieg het, die beskuldiging herhaal. Maar slegs 3 van die 57 mense wat gedood is, was in die aangewese buite-perksone-en twee van hulle het toestemming gehad om daar te wees. Die enigste persoon wat onwettig in die gevaarsone was, was die een wat mense geneig is om te onthou van die uitbarsting - Harry R. Truman, wat geweier het om sy lodge aan die suidkant van Spirit Lake, onder die noordelike flank van die berg, te verlaat.

Robin Lindley: Hoe het die meeste sterftes plaasgevind? Is sterftes veroorsaak deur hitte of versmoring of begrawe in as of ander redes?

Steve Olson: Die meerderheid van die slagoffers het versmoor toe hulle vasgevang is in die ontploffingswolk, wat uit as, warm rots en vulkaniese gasse bestaan ​​het. Maar ander is van rantoppe af geblaas, deur bome wat val, getref en deur modderstrome meegevoer. Die lyke van byna die helfte van die vermoorde mense is nooit gevind nie en bly begrawe rondom die berg.

Robin Lindley: Lodge -eienaar Harry Truman is waarskynlik die bekendste persoon wat in die uitbarsting gesterf het. Het u iets nuuts geleer oor die standvastige en koppige meneer Truman?

Steve Olson: In die weke voor die uitbarsting en na sy dood word Harry Truman gereeld deur die media uitgebeeld as 'n held wat trots en uitdagend uitgehou het teen 'n oppasser -staatsregering wat hom in veiligheid wou bring. Maar van naderby was die situasie ingewikkelder. Harry se teenwoordigheid naby die berg het ander mense 'n bedingingsbrief gegee om personeellede onder druk te sit om hulle in die gevaarsones te laat ingaan, en diegene wat daarin geslaag het om te klim, is gelukkig dat die ontploffing plaasgevind het.

Harry het geweet dat hy in groot gevaar verkeer en was bang vir wat die berg aan hom sou doen. Maar nadat hy in die media opgebou is, het hy 'n reputasie gehad. Hy was ook 83, sy vrou het 'n paar jaar tevore skielik gesterf, hy het baie gedrink. Dit is waarskynlik eerlik om te sê dat Harry Truman die lot bereik het wat hy sou gehoop het dat hy sou ontmoet.

Robin Lindley: Was daar ooit 'n formele ondersoek waarom mense op 18 Mei op die berg was en hoe die beperkte gebiede geskep en toegepas is?

Steve Olson: Daar was verhore waarop geoloë en openbare amptenare getuig het. Maar die gevolg is waarskynlik 'n regsgeding wat deur verskeie families van slagoffers teen die staat (wat ontslaan is) en teen Weyerhaeuser. Die saak teen Weyerhaeuser het in 1985 in King County tereggestaan ​​en in 'n hangende jurie geëindig. Die meerderheid van die jurielede was oortuig dat Weyerhaeuser nie die skuld gehad het om nie meer inligting aan sy werknemers te gee oor die gevare van so naby die berg nie, maar 'n vaste minderheid was dit nie eens nie. In plaas daarvan om op 'n nuwe verhoor aan te dring, het die gesinne vir 'n klein bedrag geld genadig en gesê dat hul bedoeling meer was om die name van die dooies op te klaar as om 'n groot skikking te maai.

Robin Lindley: Het die staat sy verantwoordelikheid om die burgers veilig te hou, oortree?

Steve Olson: Ja. Die gevaarsones in die weste en noordweste van die berg was te klein, en die staat was daarvan bewus. In die week voor die uitbarsting van 18 Mei was 'n gesamentlike poging onder leiding van plaaslike wetstoepassers aan die gang om die gevaarsone na die weste uit te brei, wat 'n groot deel van die gebied sou insluit waar die 57 slagoffers dood is. 'N Voorstel om dit te doen is op Saterdag 17 Mei op die lessenaar van Dixy Lee Ray gelê, maar sy was die naweek by 'n parade en het nie na haar kantoor gegaan nie. Die voorstel het nog op haar lessenaar gesit toe die vulkaan Sondagoggend uitgebars het.

Robin Lindley: Mount St. Helens is nou deels 'n nasionale monument as gevolg van die pogings van natuurbewaarders en omgewingsbewustes. Het kommersiële belange hierdie benaming nie weerstaan ​​nie? Kan houtkap, mynbou of ander belange die monument steeds ontgin?

Steve Olson: Weyerhaeuser en die ander maatskappye wat grond in die gebied besit het, het hul belange beskerm, soos verwag sou word. Maar hulle werk ook saam met die staat en federale regerings om die monument te vestig en grond wat hulle in die monument besit, te verruil vir grond buite die monument. Vandag teken Weyerhaeuser steeds die grond wat hy besit om die monument aan, en word nog ondersoekende skagte geboor op ou mynbou -eise, wat tot groot opelugmyne op die grens van die monument kan lei.

Robin Lindley: U merk op dat wetenskaplikes baie geleer het oor vulkane en meer uit die uitbarsting van die Mount St. Helens. Wat is 'n paar van die lesse uit hierdie groot gebeurtenis?

Steve Olson: Eerstens, amptenare van openbare veiligheid sal nooit toelaat dat mense so naby 'n gevaarlike vulkaan kom nie, alhoewel elke vulkaan anders is, en hulle almal die vermoë het om te verras. Wetenskaplik bestudeer Amerikaanse geoloë sedert die uitbarsting Mount St. Helens noukeurig en het hulle baie meer geleer oor die tekens wat 'n uitbarsting voorafgaan, soveel dat hulle elke uitbarsting van Mount St. Helens wat sedertdien plaasgevind het, kon voorspel. daardie datum. Die tegnologie is ook soveel meer gesofistikeerd as destyds, wat die begrip van vulkaniese gedrag verder verhoog het.

Robin Lindley: Wat het u geleer van u lesers en mense wat vertroud was met die verhaal van die uitbarsting sedert u boek uitgekom het?

Steve Olson: Mense het my gekontak om my hul stories van daardie dag te vertel. Ek het nog nie van iets gehoor wat my sou vereis om veranderinge in die sagtebanduitgawe van die boek aan te bring nie, maar ek hoop dit wel. Ek het probeer om die geskiedenis so akkuraat as moontlik te kry, maar ek weet dat geskrewe geskiedenis slegs 'n poging is om naby die waarheid te kom, nie om dit heeltemal vas te lê nie.

Robin Lindley: Dankie Steve vir u insigte en deurdagte kommentaar. En baie geluk met jou baanbrekende en onthullende nuwe boek.

Steve Olson: Dankie, Robin. Dit is 'n boeiende verhaal. Ek geniet dit altyd om daaroor te praat.


Mount St Helens -uitbarsting - Geskiedenis

Mount St. Helens, geleë in die suidweste van Washington ongeveer 50 kilometer noordoos van Portland, Oregon, is een van verskeie
verhewe vulkaniese pieke wat die Cascade Range van die noordweste van die Stille Oseaan oorheers, strek die reeks vanaf Mount
Garibaldi in British Columbia, Kanada, na Lassen Peak in die noorde van Kalifornië. Geoloë noem Mount St. Helens a
saamgestelde vulkaan (of stratovulkaan), 'n term vir steil, dikwels simmetriese keëls wat uit wisselende lae bestaan
lawastrome, as en ander vulkaniese puin. Saamgestelde vulkane is geneig om plofbaar uit te bars en aansienlik te vorm
gevaar vir lewe en eiendom in die omgewing. Daarteenoor is die saggies skuins skildvulkane, soos dié in Hawaii, tipies
ontplof nie -eksplosief en produseer vloeibare lavas wat groot afstande van die aktiewe vents kan vloei. Alhoewel Hawaïaans-tipe
uitbarstings kan eiendom vernietig, dit veroorsaak selde dood of besering. Voor 1980, sneeubedek, grasieus simmetries
Mount St. Helens was bekend as die "Fujiyama van Amerika." Mount St. Helens, ander aktiewe Cascade -vulkane, en
dié van Alaska vorm die Noord-Amerikaanse segment van die Stille Oseaan & quot; Ring van Vuur, & quot; 'n berugte gebied wat produseer
gereelde, dikwels vernietigende, aardbewings en vulkaniese aktiwiteite.

Sommige Indiërs van die Stille Oseaan Noordwes het Mount St.
moderne naam, Mount St. Helens, is in 1792 aan die vulkaniese piek gegee deur kaptein George Vancouver van die Britte
Royal Navy, 'n seevaarder en ontdekkingsreisiger. Hy noem dit ter ere van 'n landgenoot, Alleyne Fitzherbert, wat die
titel Baron St. Helens en wat destyds die Britse ambassadeur in Spanje was. Vancouver het ook drie ander genoem
vulkane in die Cascades-Mounts Baker, Hood en Rainier-vir Britse vlootbeamptes.

Indiane aan die Cowlitzrivier kyk na 'n uitbarsting van Mount St. Helens, soos geskilder deur die Kanadese kunstenaar Paul Kane
na 'n besoek aan die vulkaan in 1847 (Foto met vergunning van die Royal Ontario Museum).

Die plaaslike Indiërs en vroeë intrekkers in die destyds yl bevolkte gebied was af en toe getuie van gewelddadige uitbarstings van
Mount St. Helens. Die vulkaan was veral onrustig in die middel van die 19de eeu, toe dit af en toe aktief was
minstens 'n tydperk van 26 jaar van 1831 tot 1857. Sommige wetenskaplikes vermoed dat Mount St. Helens ook sporadies aktief was
gedurende die drie dekades voor 1831, insluitend 'n groot plofbare uitbarsting in 1800. Hoewel geringe stoomontploffings
moontlik in 1898, 1903 en 1921 plaasgevind het, het die berg min of geen bewyse getoon dat dit 'n vulkaniese gevaar is nie
meer as 'n eeu na 1857. Gevolglik het die meerderheid van die 20ste-eeuse inwoners en besoekers aan Mount St.
Helens nie as 'n bedreiging nie, maar as 'n rustige, pragtige bergspeelplek wemel van wild en beskikbaar vir ontspanning
aktiwiteite deur die jaar. Aan die voet van die vulkaan se noordelike flank, Spirit Lake, met sy helder, verfrissende water
en beboste oewers, was veral gewild as 'n ontspanningsgebied vir stap, kampeer, visvang, swem en vaar.

Die rustigheid van die berg St.
uit sy lang rus, geskud, opgeswel en weer ontplof. Die plaaslike mense het herontdek dat hulle 'n aktiewe persoon het
vulkaan in hul midde, en miljoene mense in Noord-Amerika is daaraan herinner dat die aktiewe-en moontlik
gevaarlik-vulkane in die Verenigde State is nie beperk tot Alaska en Hawaii nie.

Vorige Eruptive History

Die verhaal van Mount St. Helens is geweef uit geologiese bewyse wat ingesamel is tydens studies wat met luitenant begin het
Charles Wilkes se Amerikaanse verkenningsekspedisie in 1841. Baie geoloë het Mount St. Helens bestudeer, maar die werk van
Dwight R. Crandell, Donal R. Mullineaux, Clifford A. Hopson en hul medewerkers, wat aan die einde van hul studies begin het
1950's, het veral gevorderde kennis van Mount St. Helens. Hulle sistematiese studies van die vulkaniese afsettings,
laboratoriumondersoeke van steen- en asmonsters, en radiokoolstof (koolstof-l4) datering van plantreste begrawe in of
onder die aslae en ander vulkaniese produkte het hulle 'n merkwaardige volledige rekord van die
prehistoriese uitbarstingsgedrag van Mount St. Helens.

Voorvaderberg St. Helens het begin groei voordat die laaste groot gletsering van die ystydperk ongeveer 10 000 geëindig het
jare terug. Die oudste asafsettings het minstens 40 000 jaar gelede op 'n erodeerde oppervlak van nog ouer mense uitgebars
vulkaniese en sedimentêre gesteentes. Intermitterende vulkanisme duur voort nadat die gletsers verdwyn het en nege hoofpulse
van die vulkaniese aktiwiteit voor 1980 erken is. Hierdie tydperke het van ongeveer 5 000 jaar tot minder as 100 jaar geduur
jaar elk en is geskei met rustende tussenposes van ongeveer 15 000 jaar tot slegs 200 jaar. 'N Voorloper van Gees
Lake is ongeveer 3 500 jaar gelede, of moontlik vroeër, gebore toe uitbarstingsrommel 'n natuurlike dam oor die dam gevorm het
vallei van die North Fork van die Toutle -rivier. Die mees onlangse uitbarstingsperiode voor 1980 begin ongeveer 1800 nC
met 'n plofbare uitbarsting, gevolg deur 'n paar ekstra klein ontploffings en lava -ekstrusies, en eindig met die
vorming van die Goat Rocks -lawa -koepel teen 1857.

Die post-A.D. 1400 segment van die 50 000 jaar lange uitbarstingsgeskiedenis van Mount St. Helens (na USGS Bulletin 1383-C).

Mount St. Helens is die jongste van die groot Cascade -vulkane, in die sin dat sy sigbare kegel heeltemal
gevorm gedurende die afgelope 2 200 jaar, baie na die smelt van die laaste van die ystydperk -gletsers ongeveer 10 000 jaar gelede.
Die gladde, simmetriese hellings van Mount St. Helens word min geraak deur erosie in vergelyking met die ouer, meer gletserige
geskende bure-Mount Rainier en Mount Adams in Washington, en Mount Hood in Oregon. As geologiese studies
vorder en die uitbarstingsgeskiedenis van die berg St. Helens word beter bekend, wetenskaplikes word toenemend
bekommerd oor moontlike hernude uitbarstings. Wyle William T. Pecora, 'n voormalige direkteur van die USGS, is aangehaal
in 'n koerantberig in die Christian Science Monitor van 10 Mei 1968 as 'veral bekommerd oor sneeubedekking'
Mount St. Helens. & Quot

Op grond van sy jeug en die hoë frekwensie van uitbarstings die afgelope 4000 jaar, het Crandell, Mullineaux en hul
kollega Meyer Rubin het in Februarie 1975 gepubliseer dat Mount St. Helens die enigste vulkaan in die land is
Die Verenigde State sal heel moontlik weer wakker word en moontlik voor die einde van hierdie eeu uitbars. "Hierdie profetiese gevolgtrekking
is in 1978 gevolg deur 'n meer gedetailleerde verslag waarin Crandell en Mullineaux hul vroeëre gevolgtrekking uitgebrei het
en ontleed, met kaarte en scenario's, die soorte, omvang en oppervlakte van moontlike vulkaniese gevare wat
verwag kan word van toekomstige uitbarstings van Mount St. Helens. Gesamentlik bevat hierdie twee publikasies een van die
akkuraatste voorspellings van 'n gewelddadige geologiese gebeurtenis.

Herontwaking en aanvanklike aktiwiteit

'N Uitsig na die noorde van die & quottwo-tone & quot berg-'n voorkoms wat deur heersende oostewinde tydens die aanvanklike
aktiwiteit van Mount St. Helens. Mount Rainier is sigbaar in die agtergrond (Foto deur C. Dan Miller).

'N Aardbewing van 4,2 (Richterskaal) op 20 Maart 1980 om 15:47 Pacific Standard Time (PST), voorafgegaan
deur verskeie baie kleiner aardbewings wat reeds op 16 Maart begin het, was die eerste belangrike aanduiding van Mount St.
Helens ontwaak uit sy slaap van 123 jaar. Aardbewingaktiwiteit het gedurende die daaropvolgende week geleidelik toegeneem
en dan taamlik dramaties omstreeks 12:00 op 25 Maart. Die aantal aardbewings wat daagliks aangeteken word, bereik 'n hoogtepunt
vlakke in die volgende 2 dae, waartydens 174 skokke met 'n grootte groter as 2,6 aangeteken is. Baie honderde van
kleiner aardbewings het hierdie groter gebeurtenisse vergesel, waarvan die grootste gevoel is deur mense wat naby die
vulkaan. Lugwaarnemings van Mount St. Helens gedurende die week van seismiese opbou het klein onthul
aardbewings veroorsaak sneeustortings van sneeu en ys, maar geen teken van 'n uitbarsting nie.

Met 'n donderende ontploffing, of moontlik twee byna gelyktydig, wat omstreeks 12:36 wyd in die streek gehoor word
PST op 27 Maart begin Mount St. Helens as en stoom begin spuug, wat die eerste beduidende uitbarsting in die mark was
deurlopende Verenigde State sedert dié van Lassen Peak, Kalifornië, van 1914 tot 1917. Die kroon van die askolom
tot ongeveer 6 000 voet bo die vulkaan gestyg. Die aanvanklike ontploffings het 'n krater van 250 voet in die groter,
bestaande sneeu- en ysgevulde topkrater, en nuwe breuke het oor die topgebied gebreek.

View of the "bulge" on the north face of Mount St. Helens, from a measurement site about 2 miles to the northeast
(Photograph by Peter Lipman). The drawing above the photograph illustrates, in a highy exaggerated fashion, the
nearly horizontal movement--about 85 feet in 20 days--of one of the measured points on the "bulge."


Mount St Helens eruption - History

The story of Mount St. Helens is woven from geologic evidence gathered during studies that began with Lieutenant Charles Wilkes' U.S. Exploring Expedition in 1841. Many geologists have studied Mount St. Helens, but the work of Dwight R. Crandell, Donal R. Mullineaux, Clifford P. Hopson, and their associates, who began their studies in the late 1950's, has particularly advanced knowledge of Mount St. Helens. Their systematic studies of the volcanic deposits, laboratory investigations of rock and ash samples, and radiocarbon (carbon-l4) dating of plant remains buried in or beneath the ash layers and other volcanic products enabled them to reconstruct a remarkably complete record of the prehistoric eruptive behavior of Mount St. Helens.

Ancestral Mount St. Helens began to grow before the last major glaciation of the Ice Age had ended about 10,000 years ago. The oldest ash deposits were erupted at least 40,000 years ago onto an eroded surface of still older volcanic and sedimentary rocks. Intermittent volcanism continued after the glaciers disappeared, and nine main pulses of pre-1980 volcanic activity have been recognized. These periods lasted from about 5,000 years to less than 100 years each and were separated by dormant intervals of about 15,000 years to only 200 years. A forerunner of Spirit Lake was born about 3,500 years ago, or possibly earlier, when eruption debris formed a natural dam across the valley of the North Fork of the Toutle River. The most recent of the pre-1980 eruptive periods began about A.D. 1800 with an explosive eruption, followed by several additional minor explosions and extrusions of lava, and ended with the formation of the Goat Rocks lava dome by 1857.

The post-A.D. 1400 segment of the 50,000-year eruptive history of Mount St. Helens (after USGS Bulletin 1383-C).

Mount St. Helens is the youngest of the major Cascade volcanoes, in the sense that its visible cone was entirely formed during the past 2,200 years, well after the melting of the last of the Ice Age glaciers about 10,000 years ago. Mount St. Helens' smooth, symmetrical slopes are little affected by erosion as compared with its older, more glacially scarred neighbors--Mount Rainier and Mount Adams in Washington, and Mount Hood in Oregon. As geologic studies progressed and the eruptive history of Mount St. Helens became better known, scientists became increasingly concerned about possible renewed eruptions. The late William T. Pecora, a former Director of the USGS, was quoted in a May 10, 1968, newspaper article in the Christian Science Monitor as being "especially worried about snow-covered Mt. St. Helens."

On the basis of its youth and its high frequency of eruptions over the past 4,000 years, Crandell, Mullineaux, and their colleague Meyer Rubin published in February 1975 that Mount St. Helens was the one volcano in the conterminous United States most likely to reawaken and to erupt "perhaps before the end of this century." This prophetic conclusion was followed in 1978 by a more detailed report, in which Crandell and Mullineaux elaborated their earlier conclusion and analyzed, with maps and scenarios, the kinds, magnitudes, and areal extents of potential volcanic hazards that might be expected from future eruptions of Mount St. Helens. Collectively, these two publications contain one of the most accurate forecasts of a violent geologic event.


A Timeline of Mount St. Helens

The stratovolcano known as Mount St. Helens or Loowit formed when the Juan de Fuca tectonic plate subducted under the North American one.

The volcano experiences what scientists consider its biggest eruption ever, of 5­–10 cubic kilometers of material, about five to ten times bigger than 1980.

A series of lava flows begins to form the edifice we now know as Mount St. Helens, making the peak younger than the Great Pyramids of Giza.

1792

Explorer George Vancouver names the peak after fellow Brit—Alleyne Fitzherbert, Baron St. Helens. The local Native American tribe had long called it Lawetlat'la, or “smoker.”

Spirit Lake circa summer 1968.

► 1950s­­–1970s

Spirit Lake, at the foot of the mountain, becomes a camping and fishing destination, lined with cabins, a YMCA camp, and the Mount St. Helens Lodge run by colorful WWI vet Harry Truman (nope, no relation).

March 27, 1980

Steam emerges from near the top of the mountain, marking the beginning of an eruption. It was preceded by several small earthquakes, a sign that magma was moving deep in the ground.

Spring 1980

Geologists converge on Vancouver, Washington, including 30-year-old U.S. Geological Survey volcanologist (and University of Washington PhD grad) David A. Johnston. No one’s ever been able to study an eruption like this up close before.

April 1980

Officials designate red (dangerous) and blue (permitted workers only) zones around the mountain most residents are evacuated, though 83-year-old Truman refuses to leave, remaining in his cabin with 16 cats.

The last photo taken of David Johnston, on May 17, 1980. This site would eventually be re-named "Johnston Ridge" in his honor.

► May 18, 1980

A sunny Sunday begins with a 5.1-magnitude quake, leading to the largest landslide in recorded history and a lateral eruption of magma that flattens 600 square kilometers of forest. Johnston, perched on a ridge just to the north, radios to colleagues just before he’s instantly killed by the blast: “Vancouver, Vancouver, this is it!”

May 18, 1980

Fifty-seven people die—largely from asphyxiation—mostly in areas outside the red and blue zones, most fishing, camping, and hiking. A lahar, or mud flow, races down the Toutle River.

May 18, 1980, eruption column.

► May 18, 1980

The eruptive event ends about nine hours later, after a column of ash rises 18 miles in the air and some 1,300 feet of mountain blows off, reducing the height of Mount St. Helens to 8,366 feet.

May 1980

Ash coats the Pacific Northwest and drifts as far east as Wyoming 540 million tons fall in total.

Summer 1980

Smaller eruptive activity continues through October, as geologists get the chance to study a major eruption firsthand. A few, visiting from volcano hotspot Hawaii, roast a pig on the pyroclastic flow, aka the scorching hot gas emissions. (The annual barbecue tradition still continues among USGS Cascades Volcano Observatory scientists, albeit in someone’s backyard.)

1982

Congress designates Mount St. Helens as America’s first National Volcanic Monument.

2004–8

A four-year eruption series looks markedly different from its famous 1980 predecessor. Though less instantly dramatic, these events include plumes of ash and lava extrusion that eventually build a dome 1,000 feet high.

2020

Mount St. Helens has rebuilt about 7 percent of the mass it lost in the explosive 1980 eruption.


Mount St Helens eruption - History

Mount St. Helens, famous for its explosive 1980 eruption, has long been the most active volcano in the Pacific Northwest. U.S. Geological Survey (USGS) scientists have documented the volcano's 300,000- year geologic history, including powerful explosions of ash, outpourings of lava, and huge landslides and volcanic mudflows. Understanding this history helps USGS scientists evaluate current activity at Mount St. Helens so that timely warnings of hazards can be issued to the public.

On May 18, 1980, Mount St. Helens, Washington, exploded in a spectacular and devastating eruption that brought the volcano to the attention of the world. Few people realized that Mount St. Helens had long been the most active volcano in the Cascade Range of the Pacific Northwest. It has a rich and complex 300,000-year history and has produced both violent explosive eruptions of volcanic ash and pumice and relatively quiet outpourings of lava. The volcano's edifice was mostly built by lava domes and flows from numerous eruptions. Using evidence in these lavas and other deposits, U.S. Geological Survey (USGS) scientists have documented dozens of major individual eruptions of the volcano.

An extensive apron of ash and fragmented volcanic rocks surrounds Mount St. Helens and mostly fills the valleys draining its slopes. This material was transported by pyroclastic flows (searingly hot flows of ash and volcanic gases), lahars (volcanic mudflows), and debris avalanches (landslides). Farther away from the volcano, pumice and ash that fell during explosive eruptions form layers that bury the landscape to depths of 10 feet or more.

The pre-1980 eruptive history of Mount St. Helens is strongly episodic. Volcanologists have recognized and named four episodes of volcanic activity, called "stages"-- Ape Canyon, Cougar, Swift Creek, and Spirit Lake--separated by dormant intervals. The youngest stage, Spirit Lake, is further subdivided into six eruptive periods. Because the preservation of deposits and other geologic evidence is best for the youngest stages, the farther scientists look back in time the less detail they can infer for the history of volcanism at Mount St. Helens.

Mount St. Helens rises majestically above surrounding forests in this photo taken on May 17, 1980. In the devastating eruption the following day, 57 people were killed, most of the forest destroyed, and 1,300 feet of volcanic rock removed from the volcano's edifice, lowering its summit elevation to 8,364 feet (inset photo). During the volcano's 300,000-year history, dozens of eruptions have repeatedly changed its appearance. (USGS photos by Harry Glicken and Lyn Topinka.)

Ape Canyon Stage (300 to 35 ka)

The early history of Mount St. Helens is poorly known, and a long timespan is covered by the Ape Canyon Stage. During this stage, lava domes erupted west of the present edifice of the volcano in two distinct periods--one from 300 to 250 thousand years ago (ka) and a second from 125 to 35 ka. A number of ash layers, called the "C" set, are clearly related to volcanism during the younger phase of the Ape Canyon Stage, and a few ashes found in central Washington older than the C set are also from Mount St. Helens. Although some Ape Canyon-age lava domes are exposed in the area of Goat Mountain and Butte Camp, the best record of early Mount St. Helens volcanism is preserved in the Cougar-age debris avalanche (see below) and in glacial deposits and lahars in the Lewis River Valley.

Many Ape Canyon-age rocks were altered hydrothermally (by volcanically heated ground water), indicating that an extensive hydrothermal system existed during the latter part of the stage. Volcanism during the Ape Canyon Stage produced a small cluster of lava domes with maximum elevations of about 4,000 feet.

[Dormant Interval 35 to 23 ka]

Cougar Stage (23 to 17 ka)

The Cougar debris avalanche was followed by a large explosive eruption producing pyroclastic flows that buried the avalanche deposits with a 300-foot-thick sheet of dacite pumice (the "2-pumice pf"). (Dacite is volcanic rock containing 63 to 68% silica [SiO2].) Continued explosive activity deposited ash sets "M" and "K" and more pyroclastic flows (the "white pumice"). The Cougar Stage culminated with the eruption of the largest lava flow in the history of Mount St. Helens (Swift Creek flow). The vent for this andesite (53 to 63% SiO2) lava flow, at an elevation of 6,000 feet on the south flank of Mount St. Helens, marks the summit of the volcano at that time.

[Dormant Interval 17 to 13 ka]

Swift Creek Stage (13 to 11 ka)

All three fans are associated with the deposition of ash set "S" dated at 13 to 12.5 ka. The Swift Creek Stage culminated with deposition of ash set "J" at about 11.5 to 11 ka. At the end of Swift Creek time, Mount St. Helens consisted of a cluster of dacite domes with elevations as high as 7,000 feet.

[Dormant Interval 11 to 3.9 ka]

Spirit Lake Stage (3.9 ka to present)

This map, originally produced by the U.S. Geological Survey in 1919, shows the pre-1980 topography of Mount St. Helens. The gentle slopes on the flanks of the volcano are fans of volcanic debris and consist of ash, pumice, and volcanic rock fragments. Dashed lines show the extent of these fans.

Smith Creek Eruptive Period (3.9 to 3.3 ka)--During this period, Mount St. Helens erupted mostly ash. Two periods of activity, about 3.90 to 3.85 ka and 3.5 to 3.3 ka, deposited set "Y" ashes. The second period was initiated with an eruption that produced "Yn" ash. This eruption, possibly the most voluminous in Mount St. Helens' history, was about four times larger than the 1980 eruption. During late Smith Creek time, huge lahars swept down the Toutle River, and some probably reached the Columbia River. The primarily ash-producing eruptions of Mount St. Helens during Smith Creek time did not significantly change the volcano's shape.

Pine Creek Eruptive Period (2.9 to 2.55 ka)--During the Pine Creek Eruptive Period, Mount St. Helens erupted ash and produced pyroclastic flows and dacite domes, and two small debris avalanches occurred on its north flank. Repeated collapse of hot, growing lava domes produced an extensive and broad fan of volcanic debris as much as 600 feet thick on the south flank of the volcano. Similar deposits on the north flank can still be found as far downstream as the town of Toutle. Pine Creek-age dacite domes exposed in the walls of the crater left by the 1980 eruption show that at the end of Pine Creek time, the volcano was a cluster of lava domes with a maximum elevation of about 7,000 feet.

Castle Creek Eruptive Period (2.55 to 1.895 ka)--The Castle Creek Eruptive Period produced many lava flows and domes, pyroclastic flows, and ash. Andesite lava flows and ash erupted from the summit were emplaced on all flanks of Mount St. Helens between 2.55 and about 2.50 ka. A lull of about 300 years followed, and volcanism resumed at about 2.2 ka with eruption of andesite lava flows on the volcano's north flank. Several thick dacite lava flows and domes, pyroclastic flows and ash, and lahars were produced at 2.0 ka. Castle Creek activity culminated with eruption of three groups of fluid basalt lava flows that poured down all flanks of the volcano as far as 8 miles. The Cave Basalt, erupted at 1.895 ka, was the most recent of these. Castle Creek lavas transformed the Pine Creek-age cluster of domes into a classic cone-shaped composite volcano, with a summit elevation of about 8,500 feet.

CHRONOLOGY OF ERUPTIVE ACTIVITY AT MOUNT ST. HELENS

This simplified chronology shows the volcanic history of Mount St. Helens from its earliest beginnings about 300,000 years ago (300 ka) to its devastating and deadly eruption on May 18, 1980. The major volcanic deposits of each stage and period are listed to the right of the time columns. Lava and ash erupted by the volcano are mostly dacite (volcanic rock containing 63 to 68% silica [SiO2]), but also include andesite (53 to 63% SiO2) and basalt (less than 53% SiO2). Pyroclastic flows are searingly hot flows of ash and volcanic gases, and lahars are volcanic mudflows. "Dormant" intervals are time periods during which no volcanic activity is known. The diagram below shows how Mount St. Helens evolved from a small cluster of dacite lava domes to a moderate-size conical volcano.

The Profile of Mount St. Helens Through Time

THE HISTORY OF MOUNT ST. HELENS IS WRITTEN IN LAYERS OF ASH

By examining layers of volcanic ash (tiny jagged particles of volcanic rock and glass) and pumice deposited by successive explosive eruptions, U.S. Geological Survey scientists have deciphered the eruptive history of Mount St. Helens. Groups or "sets" of ash layers of similar age are designated with letters and signify explosive episodes in the volcano's history. Ages of ash layers less than 50,000 years old are determined by radiocarbon dating of wood or charcoal trapped in the ash. The 20-foot-high cliff at "Stratigraphy Viewpoint" along the Muddy River (photo above) exposes a series of deposits from the past 13,000 years of Mount St. Helens' history. The prominent yellow-brown layer in the middle is part of ash set "Y" from the Smith Creek Eruptive Period. The cliff is capped by deposits several feet thick from the volcano's devastating 1980 eruption. Major explosive eruptions not only leave deposits near the volcano but also inject fine ash (see inset photo) high into the atmosphere, where wind can carry it great distances. The map shows the known distribution of recognizable ash layers from three fairly typical explosive eruptions of Mount St. Helens in the past few thousand years. The eruption that produced the "Yn" ash was about four times as large as that of 1980 and was probably the largest explosive eruption in the volcano's history.

Sugar Bowl Eruptive Period (1.2 to 1.15 ka [A.D. 850 to 900, corrected radiocarbon dates])--During the Sugar Bowl Eruptive Period, three lava domes were built on the flanks of Mount St. Helens. Explosive eruptions associated with growth of the Sugar Bowl Dome produced two "lateral blasts" that affected an area about one-tenth as large as that of the lateral blast in the 1980 eruption. Ash layer "D" and lahars were also emplaced. The Sugar Bowl period was short lived, produced a small volume of volcanic materials, and did not significantly change the appearance of the volcano.

Kalama Eruptive Period (A.D. 1479 to 1720)--Activity during this period produced large-volume dacite ashes, pyroclastic flows, domes, lahars, and andesite lava flows. Mount St. Helens added about 1,000 feet of elevation and attained its pre-1980 form during the Kalama Period. The Kalama Eruptive Period is subdivided into three series of events the early, middle, and late Kalama phases.

The early Kalama phase began in 1479 with a large pyroclastic eruption that deposited dacite ash layer "Wn." In 1482, a smaller eruption produced ash layer "We." Over the next 10 to 20 years, a number of lava domes grew in the volcano's crater and were disrupted by explosive eruptions. Lahars and pyroclastic flows associated with early Kalama eruptions are abundant on the volcano's west and south flanks.

The middle Kalama phase began about 1510 with eruption of andesite as pyroclastic flows (which generated hot lahars), a few lava flows, and ash set "X." The middle phase peaked about 1535 with eruption of the many thick andesite lava flows prominent on all flanks of Mount St. Helens, including the Worm Complex flows, and ended by 1570.

The most significant event of the late Kalama phase was growth of a large dacite dome at the summit (Summit Dome). The Summit Dome took nearly 100 years to grow (1620 to 1720) and gave Mount St. Helens its pre-1980 form. During growth, it shed material as pyroclastic flows and lahars on all flanks of the volcano. Mount St. Helens acquired its pre- 1980 cover of glaciers as a result of growth of the Summit Dome.

Goat Rocks Eruptive Period (A.D. 1800 1857)--The Goat Rocks Period was short and relatively small. An explosive eruption in 1800 produced ash layer "T" and was followed in 1801 by an andesite lava fl ow, called the "Floating Island," on Mount St. Helens' north fl ank. Eruptions observed intermittently from 1831 to 1857 produced ash and the Goat Rocks Dome, whose growth also resulted in a small fan of volcanic debris and lahars.

The last significant eruption of Mount St. Helens before 1980 is generally considered to have occurred in 1857. Minor explosions reported in 1898, 1903, and 1921 were probably steam-driven and not magmatic (molten rock) eruptions. Eruptions of the Goat Rocks Period did not significantly change the appearance of Mount St. Helens, but they added the final pieces to the edifice and set the stage for the 1980 eruption.

Recent work by scientists with the USGS in cooperation with the U.S. Forest Service is shedding new light on the 300,000-year history of Mount St. Helens Volcano. The work of these USGS scientists is only part of the USGS Volcano Hazards Program's ongoing efforts to protect people's lives and property in all of the volcanic regions of the United States, including the Pacifi c Northwest, eastern California, Wyoming, Alaska, and Hawaii.

Michael A. Clynne, David W. Ramsey, and Edward W. Wolfe

Edited by James W. Hendley II and Peter H. Stauffer
Graphic design by Susan Mayfield and Sara Boore Web design by Michael Diggles


1980 Cataclysmic Eruption

Magma began intruding into the Mount St. Helens edifice in the late winter and early spring of 1980. By May 18, the cryptodome (bulge) on the north flank had likely reached the point of instability, and was creeping more rapidly toward failure.

Annotated seismogram indicates the signals for a Low-Frequency (LF) volcanic earthquake, relative quiescence, and then harmonic tremor as the eruption of May 18, 1980 accelerated. Each horizontal line represents 15 minutes of time. (Public domain.)

Summary of Events

On May 18, 1980, a magnitude-5+ earthquake was accompanied by a debris avalanche, which in turn unloaded the confining pressure at the top of the volcano by removing the cryptodome. This abrupt pressure release allowed hot water in the system to flash to steam, which expanded explosively, initiating a hydrothermal blast directed laterally through the landslide scar. Because the upper portion of the volcano was removed, the pressure decreased on the system of magma beneath the volcano. A wave of decreasing pressure down the volcanic conduit to the subsurface magma reservoir, which then began to rise, form bubbles (degas), and erupt explosively, driving a 9-hour long Plinian eruption.

Steam-blast eruption from summit crater of Mount St. Helens. Aerial view, April 6, looking southwest, showing a roiling, gray-brown, ash-laden cloud that envelops and almost completely hides an initial fingerlike ash column, and an upper white cloud formed by atmospheric condensation of water vapor in the convectively rising top of the eruptive column. Image and caption taken from Professional Paper 1250 and not scanned from original slide. (Credit: Moore, James G.. Public domain.)

Precursory Activity

On March 16, 1980, the first sign of activity at Mount St. Helens occurred as a series of small earthquakes. On March 27, after hundreds of additional earthquakes, the volcano produced its first eruption in over 100 years. Steam explosions blasted a 60- to 75-m (200- to 250-ft) wide crater through the volcano's summit ice cap and covered the snow-clad southeast sector with dark ash.

Within a week the crater had grown to about 400 m (1,300 ft) in diameter and two giant crack systems crossed the entire summit area. Eruptions occurred on average from about 1 per hour in March to about 1 per day by April 22 when the first period of activity ceased. Small eruptions resumed on May 7 and continued to May 17. By that time, more than 10,000 earthquakeshad shaken the volcano and the north flank had grown outward about 140 m (450 ft) to form a prominent bulge. From the start of the eruption, the bulge grew outward—nearly horizontally—at consistent rates of about 2 m (6.5 ft) per day. Such dramatic deformationof the volcano was strong evidence that molten rock (magma) had risen high into the volcano. In fact, beneath the surficial bulge was a cryptodome that had intruded into the volcano's edifice, but had yet to erupt on the surface.

Debris Avalanche

With no immediate precursors, a magnitude 5.1 earthquake occurred at 8:32 a.m. on May 18, 1980 and was accompanied by a rapid series of events. At the same time as the earthquake, the volcano's northern bulge and summit slid away as a huge landslide—the largest debris avalanche on Earth in recorded history. A small, dark, ash-rich eruption plume rose directly from the base of the debris avalanche scarp, and another from the summit crater rose to about 200 m (650 ft) high. The debris avalanche swept around and up ridges to the north, but most of it turned westward as far as 23 km (14 mi) down the valley of the North Fork Toutle River and formed a hummocky deposit. The total avalanche volume is about 2.5 km 3 (3.3 billion cubic yards), equivalent to 1 million Olympic swimming pools.

A "bulge" developed on the north side of Mount St. Helens as magma pushed up within the peak. Angle and slope-distance measurements to the bulge indicated it was growing at a rate of up to five feet (1.5 meters) per day. By May 17, part of the volcano's north side had been pushed upwards and outwards over 450 feet (135 meters). (Lipman, Peter. Public domain.)

Bulge (right) and small crater, Mount St. Helens summit. Crater area dropped in relation to the summit, and bulge shows pronounced fracturing because of its increased expansion. View looking south. (Credit: Krimmel, Robert M.. Public domain.)

Lateral Blast

Blowdown of trees from the shock-wave of the directed (lateral) blast from the May 18, 1980 eruption of Mount St. Helens. Elk Rock is the peak with a singed area on the left.

(Credit: Topinka, Lyn. Public domain.)

The landslide removed Mount St. Helens' northern flank, including part of the cryptodome that had grown inside the volcano. The cryptodome was a very hot and highly pressurized body of magma. Its removal resulted in immediate depressurization of the volcano's magmatic system and triggered powerful eruptions that blasted laterally through the sliding debris and removed the upper 300 m (nearly 1,000 ft) of the cone. As this lateral blast of hot material overtook the debris avalanche it accelerated to at least 480 km per hr (300 mi per hr). Within a few minutes after onset, an eruption cloud of blast tephra began to rise from the former summit crater. Within less than 15 minutes it had reached a height of more than 24 km (15 mi or 80,000 ft).

The lateral blast devastated an area nearly 30 km (19 mi) from west to east and more than 20 km (12.5 mi) northward from the former summit. In an inner zone extending nearly 10 km (6 mi) from the summit, virtually no trees remained of what was once dense forest. Just beyond this area, all standing trees were blown to the ground, and at the blast's outer limit, the remaining trees were thoroughly seared. The 600 km 2 (230 mi 2 ) devastated area was blanketed by a deposit of hot debris carried by the blast.

Plinian eruption column from May 18, 1980 Mount St. Helens. Aerial view from the Southwest. (Credit: Krimmel, Robert. Public domain.)

Plinian Eruption

Removal of the cryptodome and flank exposed the conduit of Mount St. Helens, resulting in a release of pressure on the top of the volcano's plumbing system. This caused a depressurization wave to propagate down the conduit to the volcano's magma storage region, allowing the pent-up magma to expand upward toward the vent opening. Less than an hour after the start of the eruption, this loss of conduit pressure initiated a Plinian eruption that sent a massive tephra plumehigh into the atmosphere. Beginning just after noon, swift pyroclastic flows poured out of the crater at 80 - 130 km/hr (50 to 80 mi/hr) and spread as far as 8 km (5 mi) to the north creating the Pumice Plain.

The Plinian phase continued for 9 hours producing a high eruption column, numerous pyroclastic flows, and ash fall downwind of the eruption. Scientists estimate that the eruption reached its peak between 3:00 and 5:00 p.m. When the Plinian phase was over, a new northward opening summit amphitheater 1.9 x 2.9 km (1.2 x 1.8 mi) across was revealed.

Ash cloud from Mount St. Helens over Ephrata, Washington (230 km (145mi) downwind), after May 18, 1980 eruption. (copyright by Douglas Miller)

Over the course of the day, prevailing winds blew 520 million tons of ash eastward across the United States and caused complete darkness in Spokane, Washington, 400 km (250 mi) from the volcano. Major ash falls occurred as far away as central Montana, and ash fell visibly as far eastward as the Great Plains of the Central United States, more than 1,500 km (930 mi) away. The ash cloud spread across the U.S. in three days and circled the Earth in 15 days.

During the first few minutes of this eruption, parts of the blast cloud surged over the newly formed crater rim and down the west, south, and east sides of the volcano. The turbulently flowing hot rocks and gas quickly eroded and melted some of the snow and ice capping the volcano, creating surges of water that eroded and mixed with loose rock debris to form lahars. Several lahars poured down the volcano into river valleys, ripping trees from their roots and destroying roads and bridges.

The largest and most destructive lahar occurred in the North Fork Toutle and was formed by water (originally groundwater and melting blocks of glacier ice) escaping from inside the huge landslide deposit through most of the day. This powerful slurry eroded material from both the landslide deposit and channel of the North Fork Toutle River. Increased in size as it traveled downstream, the lahar destroyed bridges and homes, eventually flowing into the Cowlitz River. It reached maximum size at about midnight in the Cowlitz River, about 80 km (50 mi) downstream from the volcano.

Nearly 135 miles (220 kilometers) of river channels surrounding the volcano were affected by the lahars of May 18, 1980. A mudline left behind on trees shows depths reached by the mud. (Credit: Topinka, Lyn. Public domain.)


Most destructive U.S. volcano

The 1980 Mount St. Helens eruption was the most destructive in U.S. history. Fifty-seven people died, and thousands of animals were killed, according to USGS. More than 200 homes were destroyed, and more than 185 miles of roads and 15 miles of railways were damaged. Ash clogged sewage systems, damaged cars and buildings, and temporarily shut down air traffic over the Northwest. The International Trade Commission estimated damages to timber, civil works and agriculture to be $1.1 billion. Congress approved $950 million in emergency funds to the Army Corps of Engineers, the Federal Emergency Management Agency and the Small Business Administration to help with recovery efforts.


What Actually Happened at Mount St. Helens?

One of the first places we filmed was Mount St. Helens. I knew from the start I wanted to show people how quickly a landscape could be transformed through catastrophic processes.

While researching the project, I had read Dr. Steve Austin’s book Footprints in the Ash: The Explosive Story of Mount St. Helens. I remember looking at the photos and thinking ‘I have to show people this.’

About six months later, I was with Del Tackett, Steve Austin, and our crew at the trailhead next to the Mount St. Helens Visitor Center. We were loaded down with backpacks, cameras, and gear. It had rained the past two days and this was our last day there: we had one chance to shoot the first scene of the film.

Hiking down to the Little Grand Canyon.

We began our slow march down to the ‘Little Grand Canyon’ some 4,000 feet below us. It was a 7 mile hike to the bottom. Steve was our guide, taking us off the trail and across elk paths to get to our destination. After about four hours, we found ourselves at the bottom of a deep ravine. A cold wind was blowing.

When we got there, it was pretty amazing to see in real life what Steve had been talking about. Just looking around and seeing what was a very normaal landscape, but one that hadn’t existed 40 years before, was eye-opening: how many things had I looked at and just assumed were very old because that’s what I had been taught?

We filmed Del’s opening monologue to the film, then added Steve into the picture. We had captured him the day before on the ridge far above us giving us an overview of the events, but down in the canyon he showed us all sorts of interesting things. Although none of this made the film, we have included it in our complete Beyond Is Genesis History? reeks.

Filming in the ‘Little Grand Canyon’ with Del Tackett and Steve Austin.

How Do We Know How Old Things Are?

As far as I can tell, there are only two ways of knowing what happened in the past: someone was there to see it and tell us about it, or someone looks at the residual data and tries to reconstruct it as best they know how.

It’s obvious the former is far preferable to the latter. This doesn’t mean that forensic reconstruction doesn’t have great use: it clearly does. But it does mean that when someone accurately observes an order of events, that provides a basic chronology to which we can link all the forensic data. Time is the backbone of history.

This is one of the reasons Steve Austin calls Mount St. Helens “the rosetta stone” of catastrophic geology. It actually links up eyewitness accounts of a major volcanic eruption and the decades long aftermath with the observation of forensic data. What it demonstrates is it doesn’t take nearly as long to create certain geological structures as had been previously assumed. Steve mentioned four things that I still remember:

1. Rapid Sedimentation – It is strange to realize that you are walking on a part of the earth that simply didn’t exist when you were born. We all have this assumption of stability and age when we look at landscapes in the world (even if we think the earth is only thousands of years old). And yet as we trooped down into the canyon area, Steve reminded us this was all new. When we got to the bottom and saw the many different layers, including the thin laminations and the flat boundaries, it was obvious that a lot had happened in a very short period of time.

2. Rapid Erosion – Again, we often don’t think of the various events necessary to arrive at a current landscape. In this case, when we were standing at the bottom next to the stream, it took us a while to grasp that where we were had at one time been covered with mud. In this case, at the exact place where we were, it had once been sky, then was mud, and now was a creek bed. The fact that this last step happened quickly through erosion which had been observed was remarkable.

Notice the erosion below us as we hike out.

3. Rapid Recovery – The next thing Steve pointed out was how many plants were growing in the area. He explained that in the years immediately after the eruption, animals also quickly returned to the area. This was because God created the natural world to be able to automatically fix itself and recover from catastrophes. It gave a new appreciation of how the world could have recovered relatively quickly from something even as massive as a global Flood with all the volcanism that would have gone along with it.

4. Incredible Complexity – The last thing that struck me was how complex and interrelated all the different events were that occurred, many of which were wiped out or changed by events that came after them. This demonstrates that geological processes are far from simple and straightforward, but that there is an incredibly interlocking complexity that is best unraveled by knowing the actual history of the events.

A Small Paradigm Shift

The final thing Mount St. Helens let me do was to let my audience experience a small paradigm shift on their own. In filmmaking and storytelling, there is a well-known element called a ‘reveal.’ It’s when a piece of information is withheld from a viewer, allowing them to follow a natural set of assumptions that actually isn’t accurate.

I accomplished this by having Del make two observations I knew everyone had been taught to relate to old ages: geologic processes and radioisotope dating. I knew everyone puts enormous trust in these two things because they have been taught from a young age to accept them. The former is established through the conventional explanation of the Grand Canyon which almost everyone is familiar with the latter is established through school science textbooks, teachers, films, and TV shows.

And yet the one thing the conventional view rejects is the eyewitness account. According to their view of the world, no one was there to observe the majority of the events of natural history. This applies even to Christians who have accepted the conventional view of history, since they have to see Genesis 1 as being more allegorical and Genesis 6-8 as a local flood.

However, as Mount St. Helens shows us, an eyewitness account can transform how one views the actual evidence. I wanted people to realize for themselves that there are different ways of looking at what they see around them, and that what they have been told about the geologic evolution of the earth may not be as accurate as they think.

I clearly could not get all of this information on Mount St. Helens into the documentary. I had, however, always intended to create the series ‘Beyond Is Genesis History?’ in order to provide the fuller picture. The film is just an overview and introduction the real meat is in Anderkant. The segment above with Del and Steve at Mount St. Helens is a good example of it: there’s a lot still to learn from these scientists.


Kyk die video: Mount St. Helens is about to Blow Up (Oktober 2021).