volcanic hazards - 10/2/09 Volcanoes:HazardsandMitigation...

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10/2/09 Volcanoes: Hazards and Mitigation Volcanic Hazards 0. Millions of people around world live in risk of volcanic eruptions 0. Volcanic materials give  rich, fertile soil  for agriculture 1. Majestic volcanic peaks give  beautiful vistas 2. Hawaiian climate appeals to retirees 1. Most volcanic eruptions kill no more than few hundred people Hazards from Lava Flows o Flowing basalt lava, though cooling, still hot enough to  ignite  wood structures o Flow may surround or bury structures o Lava flows usu. move slowly and cover small enough area:  pose  little threat to  human life o Rare, fluid, alkali-rich lava flows faster  Stopping the Lava Flow 0. 1973 eruption of Elfell Volcano, Iceland, sent lava flow toward fishing village of  Heimaey 1. Water pumped on flows slowed them down, saving most of town Pyroclastic Flows 2. Mixture of  hot volcanic ash and steam  that flows downhill because too dense to  rise 3. Race down side of volcano at  50-200 km/hr 4. Form as part of eruption column collapse 5. Ash-rich, shock wave  surge  may race ahead of pyroclastic flow, up to 600 km/hr 6. Hottest pyroclastic flows at 800-850 o C, hot enough to fuse into solid mass,  welded ash o Travel distance  related to  energy line  sloping downward from top of ash-rich  part of eruption column o Actual hazard distance can be much greater if eruption fueled by lateral blast  (e.g. Mt. St. Helens) o Can travel over surface of water Ash and Pumice Falls 7. Volcanic ash is composed of bits of  pumice
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8. Particles suspended in steam cloud that cools and condenses, falls in ashy rain 9. Largest ash particles fall near vent 10. Smallest ash particles remain suspended in stratosphere up to years, carried  around world, blocking radiation from sun 3. After 1815 eruption of Mount Tambora, Indonesia: “ year without a  summer 4. Mt. Pinatubo eruption cooled planet by ~1°C 0. Heavy loading of ash on roofs, when mixed with water, causes  roof collapse 1. Serious  health problems  from inhaling ash for those with existing respiratory  illness 2. Cars: hinders visibility, clogs air filters 3. Serious problems for aircraft:  loss of jet engine power , damage to engines Volcanic Mudflows 11. Ash combines with water, pours down sides of volcanoes at high speeds, like wet  concrete 12. Velocities similar to floods, spread over lower slopes 13. Can be triggered by eruption of volcano covered in ice or snow, or by heavy rain 4. Icy to boiling temperatures (hot mudflow called  lahar ) 5. Most stratovolcanoes emit steam from summit, from snow or rain meltwater 
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This note was uploaded on 02/21/2010 for the course GEOL 116 taught by Professor Kruger during the Spring '09 term at Binghamton University.

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volcanic hazards - 10/2/09 Volcanoes:HazardsandMitigation...

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