VEI 5 - Mount Pinatubo

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  • Created by: Pho3b301
  • Created on: 10-03-17 21:12

VEI 5 - Mount Pinatubo

  • Luzon Island, Philippines
  • Philippines plate subducting under Eurasian plate 
  • USA has huge military presence in the area - 2 big US airbases close by 

June 15th 1991 Eruption:

  • Triggered by Rizal City Earthquake (6.8) in 1990 
  • Not many died, mostly local tribesmen 
  • USGS predicted eruption & managed eruption 
  • USGS evacuated everyone 
  • Pyroclastic flows 
  • Explosions rocked volcano - many tribes fled 
  • 3 explosion craters, 4 columns of steam 
  • Seismometer - 400 earthquakes in 2 days 
  • Early may - 7 sites of studying volcano 5 miles below surface, Measure SO2 levels (5000 tonnes per day) suggesting rising magma
  • June 7th - Level 4 alert after frequent earthquakes - everyone within 12 miles evacuated, 120,000 left for temp homes 
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VEI 5 - Mount Pinatubo

  • Visible molten rock 
  • Early June - summit gave way, resulting in pyroclastics 
  • Pyroclastics changed direction & killed 43 people 
  • Lava dome observed 
  • Eruption occured 48 hours after air base was evacuated 
  • Lahars carried on for years after 
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VEI 5 - Mount Pinatubo

Lahars:

  • 40mph/65kmh
  • Travel 50 miles +
  • Contain as much as 90% of debris 
  • Annual rainfall at Pinatubo is 80inches to 160 inches 
  • Destroyed vegetation that was on the volcano 
  • Transported & deposited tens of millions of cubic yards of mud in a single day / 35,000cubic ft of debris & mud per second
  • 30 feet deep  
  • Damming of stream channels & tributary valleys by 1991 ash deposits or by subsequent lahars, creating temporary lakes 
  • Civil engineers tried to trap sediment behind small damns & confine it between levees (too small to contain lahars) 
  • Base of volcano - lahars erode city blocks 
  • Lowlands - inundated & buried entire towns 
  • Destroyed 100,000 homes 
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VEI 5 - Mount Pinatubo

  • By 1995 - volume of material carried by Pinatubo's lahars had decreased to less than 1/4 
  • New towns built on high ground 
  • Near system warning to monitor activity has been put in place 
  • Preliminary hazard map 
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