Slideshow 101.19 Volcano Overview II

Slideshow 101.19 Volcano Overview II - Volcano Overview II...

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Volcano Overview II Overview I covered: Factors controlling eruptions Types of eruptions (2 main) Some types of deposits Overview II covers: Pyroclastic Flows (nuée ardente) Lahars
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Volcano Overview II Volcanic Deposits Lava: Effusive deposits Non-explosive (Most commonly) 1. Ba s a ltic  La va 2. Ande s itic  La va Pyrolcastic deposits Explosive (Most commonly) 1. Ande s itic 2. Rhyo litic * *Viscous: it tends to cool underground or  explode violently.
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Volcano Overview II Pyroclastic Flow   Ground hugging currents of hot gas + tephra   Fast moving  - up to 700 km/h – speed depends on:   density of the current (how heavy)  rate volcanic output (how much how fast)  the gradient of the slope (how steep)   Hot  -  up to 1000º C Names:   pyroclastic flow (rocky) pyroclastic surge (gassy)   pyroclastic density current (general)   nuée ardente Pyroclastic flows - Mayon  Volcano, Philippines, 1984  
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Pyroclastic Flows are caused by : Eruption column   collapse Frothing at the mouth of the vent during degassing Gravitational collapse of a lava dome, with subsequent avalanching and flow down a steep slope   Directional blast (or jet) when part of a volcano explodes or collapses – often laterally Volcano Overview II Eruption of Vesuvius, 1822
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Volcano Overview II Pyroclastic Flows “nuée ardente“ Fre nc h fo r “g lo wing  c lo ud” Airb o rne  m a te ria l -  s us pe nde d “Flo a ts ” o n a  la ye r o f tra ppe d  a ir a nd m a g m a tic  g a s e s  -  re m a ins  b uo ya nt. De po s its  whe re  m a te ria l is   s o lidifie d a re  c a lle d  “ig nim b rite s ” S till ve ry ho t whe n the y s to p  flo wing  – c a n fus e s  to g e the r  to  fo rm  welded tuff
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Volcano Overview II Pyroclastic Flow - Column Collapse
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Volcano Overview II As h plum e  o f Pina tub o  during  1991 e ruptio n 
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This note was uploaded on 04/11/2008 for the course GEOL 101 taught by Professor Winstonnorrish during the Fall '07 term at Central Washington University.

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Slideshow 101.19 Volcano Overview II - Volcano Overview II...

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