Slide Number 1Slide Number 2Slide Number 3Slide Number 4Slide Number 5Slide Number 6Slide Number 7Slide Number 8Slide Number 9Slide Number 10Slide Number 11Slide Number 12Slide Number 13Slide Number 14Slide Number 15Slide Number 16Slide Number 17Slide Number 18Slide Number 19Slide Number 20Slide Number 21Slide Number 22Slide Number 23Slide Number 24Slide Number 25Slide Number 26Slide Number 27Slide Number 28Slide Number 29Slide Number 30Slide Number 31Slide Number 32Slide Number 331 2 3 4 Pyroclastic Flow, Montserratt, 1997 (Geological Survey of Canada, 2007)• Mt. St. Helens (1980, Washington) • subduction zone • lateral blast • 9-hour ash eruption to 19 km • Ash flows • mudflows (lahars)down Toutle River Valley at speeds up to 55 km/hr, reached ~100 km distance • river rose to 4 m above flood stage, destroyed bridges • 54 deaths, $3 B damage incl. 800 M board feet of timber flattened5,000 yrs., 80 km 500 yrs. 53 km Computer simulation Historic Lahars: Mt. Ranier 30 km / hr 2-3 m thickVolcanic Hazards: Lahars Mt. St. Helens, prehistoric lahar (~2,500 yrs)Cascadia Subduction Zone0 500 1000 1500 2000 2500 3000YellowstoneCrater LakeMt. St. HelensVolume Ejected (cubic km)Why do some plate boundaries not have volcanoes
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