Volcano Web Sites Ashfall Eruption Case History-Mt....
Transcript of Volcano Web Sites Ashfall Eruption Case History-Mt....
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#16- CaseStudiesofVolcanoesII
Mt. Saint Helens, Washington, 1980
VolcanoWebSites
MountSt.HelensVolcanoCams (NationalParkService)http://www.fs.fed.us/gpnf/volcanocams/msh/
VirtualfieldtriptoMountSt.Helens(Strombolionline)http://www.swisseduc.ch/stromboli/virtual-excursions/index-en.html
CascadeVolcanoAlertLevels(USGeologicalSurvey)http://volcanoes.usgs.gov/activity/status.php#cvo
PanoramicView- MountSt.Helens(Fullscreen 360)http://www.fullscreen360.com/st-helens
Osorno volcano, ChileSakurajima volcano, Japan
Ashfall EruptionCaseHistory-Mt.SaintHelensMt.St.Helens(MSH)inSWWashingtonisoneofmanyvolcanoesinCascadeMountainsinNWUS,SWCanada;subduction zonevolcano
Mt.SaintHelens- 1980EruptionMajoreruptiononMay18,1980.Before1980,itwassymmetrical
Before
After
After1980eruption,largepartofmountainexplodedaway.
Mt.SaintHelens- 1980EruptionSequence1)Pre- 5/18/80(~50days)Gas-chargedsilicicmagmafilledareabelowvolcanocausinggroundtoswell~300ft.Geologistswarnedofpossibleexplosiveeruption.
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Mt.SaintHelens- 1980EruptionSequence1)Pre5/18/80(~50days)
BulgedevelopsonnorthsideofMt.StHelens
Mt.SaintHelens- 1980EruptionSequencePre5/18/80(~50days)
BulgedevelopsonnorthsideofMt.StHelens
ClickerQuestionWhattypeofvolcanoisMountSaintHelens?A. ShieldvolcanoB. StratovolcanoC. LavaLakevolcanoD. Riftvolcano
Mt.SaintHelens- 1980EruptionSequenceMay18,1980 Twostrongearthquakes(frommagmamoving)causedlargesthistoriclandslide.Landslidereleasedpressureonmagma,causedupwardandhorizontalexplosionofvolcanicash.
Mt.SaintHelens- 1980EruptionSequenceMay18,1980 Twostrongearthquakes(frommagmamoving)causedlargesthistoriclandslide.(a)Landslide releasedpressureonmagma,causedupwardandhorizontalexplosionofvolcanicash.
Vertical and lateral blast
Mt.SaintHelens- 1980EruptionSequenceMay18,1980 (b)Enormousforceofhorizontalexplosion knockedovertreesforlargedistancesEffects of lateral blast
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Mt.SaintHelens- 1980EruptionSequenceMay18,1980 Horizontalexplosionknockedovertreesforlargedistances
Lateral blast effects - Trees blown down
Mt.SaintHelens- 1980EruptionSequenceMay18,1980 Ashblown10milesupwarddarkenedskiesfor100sofmilesand(c)causedashfall.
Vertical blast, ashfall
Mt.SaintHelens- 1980EruptionSequenceMay18,1980 Ashblown10milesupwarddarkenedskiesfor100sofmiles.
Ephrata, WA (150 miles away)
Spokane, WA (300 miles away)
Mt.SaintHelens- 1980EruptionSequenceMay18,1980 Ashblown10milesupwarddarkenedskiesfor100sofmiles(ashcarriedbyjetstreamtoeasternUS).Ashfall wasmainlynuisance.
Mt.SaintHelens- 1980EruptionSequenceMay18,1980 Ashfall wasmainlynuisance- somedisruptionofdailylife.
Mt.SaintHelens- 1980EruptionSequenceMay18,1980 Hotashmeltedsnowtoproduceenormous(d)lahar(mudflow),whichcreatedflooding.
Lahar (mudflow)
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Mt.SaintHelens- 1980EruptionSequenceMay18,1980 Hotashmeltedsnowtoproduceenormous(d)lahar(mudflow),whichcreatedflooding.
Lahar (mudflow) effects
Mt.SaintHelens- 1980EruptionSequenceMay18,1980 63peoplewerekilled,includingonegeologist(DavidJohnston).Manymoredeathswithoutwarningsfromgeologists.
David Johnston
Mt.SaintHelens- 1980EruptionTheEruptionofMt.St.Helens video(OttoSieber 13:11- 17:20)https://www.youtube.com/watch?v=fmrZXWOVuC4
ClickerQuestionWhichdidNOTcausedamageand/ordisruptionduringtheMountSaintHelens1980eruption?A. Majorlavaflowsthatburiedtowns.B. Amajorexplosiveblastthattraveledformiles.C. Lahars(volcanicmudflows).D. Ashfallsintheregion
OtherExplosivelyVolcanoesCindercone - consistsentirelyofpyroclasticdebrisofallshapesandsizes(nolavaflows).Small,symmetricalcone;usually~shortlifespan.
OtherExplosivelyVolcanoes- CinderConeParicutinvolcano inMexico,1943;builta400mhighconein9yearsthenextinguisheditself.
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VolcanoSize- Shield,Strato,CinderConeCinderconesaremuchsmallerthantypicalstratovolcanoes,whicharemuchsmallerthanshieldvolcanoesofHawaii.
OtherExplosiveVolcanoFeaturesLavadome - bulbousmassofextremelyviscouslavathataccumulatesaroundvent,whichcangetplugged;potentialforextremelyexplosiveeruption.
Lava Dome at Mt. Saint Helens, 1984
OtherExplosivelyVolcanoesCaldera - rare,butextremelyviolenteruptionthatproduceshugecrater(10'sofkmwide).
OtherExplosivelyVolcanoes
Caldera - involvelargestvolcanoexplosivity indices(VEI≥6);commonlybeginasstratovolcano,thenenormouseruptionblowsawaytoppartofvolcano.Magmachamberempties,leavinglargeundergroundcavity,groundoveritcollapses.
OtherExplosivelyVolcanoes- CalderasKrakatau (southwestPacific, 1883)createdcraterthatextended300mbelowsealevel,producedgianttsunamithatkilled>30,000people
Tambora Eruption- 1815Pre-telegraph
VEI=77kmdiametercaldera41cubickm14,000ft.mountainGONE
1816:“Yearwithoutasummer”• CropsruinedintheeasternUSA
• FamineinEuropeandIndia• Politicalinstability
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OtherExplosiveVolcanoes- CalderasMountMazama (insouthwestOregon,~6,800yearsago)createdCraterLake
OtherExplosiveVolcanoes- CalderasSantorini (Greece,1390BC)destroyedLateMinoancivilization(legendoflostcityofAtlantis?)
ClickerQuestionWhatcausesaCalderaeruption?A. Largeamountsoflowviscositymagmapoursout
ofthegroundquickly.B. Alargemagmachamberemptiesand,asitdoes,
itsroofcollapses.C. Amountainbuildsupverytallandspewsashout
ofacrateratthesummit.D. Alloftheabove.
OtherExplosivelyVolcanoes- CalderasYellowstone (northwestWY)3largecaldera-formingeruptionsoverpast2millionyears(1.9,1.3,0.6m.y.a.)600,000yearrecurrence,eruptionswere~1000timeslargerthanMountSt.Helens,
OtherExplosivelyVolcanoes- CalderasYellowstone caldera-formingeruptionswere~1000timeslargerthanMountSt.Helens
OtherExplosivelyVolcanoes- CalderasYellowstone continuestoshowsignsofactivitywithhotsprings,geysers
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OtherExplosivelyVolcanoes- CalderasYellowstone someconsiderit“supervolcano”,difficulttopredictnexteruptionprecisely,massiveonenotexpectedsoon(>10,000years?)
ClickerQuestionWhichisNOTacommonnegativeconsequenceoflargeCalderaeruptions?A. Hugeoutputofvolcanicashintotheatmosphere.B. Hugelavaflowsthatrunacrossthelandsurface.C. Coolingoftheatmosphere.D. Explosionsthatdevastatelargeareasoftheearth’s
surface(10milesormore)