Mt Pinatubo Eruption - 1991



  • Dorment for over 500 years - erupted in 1991
  • 2nd April 1991 - steam emission coming from mountain - monitored by PHIVOLCS
  • 10km radios danger zone declared
  • USGS arived with seismometers, tiltmeters and other equipment
    • monitored activity of volcano - 40 - 150 earthquakes per day
    • sulphur dioxide went from 500 tonnes to 5,000 tonnes per day in five weeks
    • volcano erupted five time in 2,000 years = explosive eruption
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  • Produced hazard maps to indicate the nature and extent of eruption

  • Earthquake frequency increased and sulphur dioxide levels decreases – magma was holding gas – eruption would be highly explosive
  • Evacuations were orders on the 3 June – 20,000 living within a 10km radius, 7th June – 120,000 people living within a 18km radius
  • Volcano erupted on 15th June – 6 days after the last evacuation
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Evaluation of preparation

  • Hazard maps were accurate – all areas affected were predicted to be affected
  • Small numbers killed – around 850 million
    • USGS/PHIVOLS estimates –
    • 5,000 to 20,000 lives saved – predictions and evacuations
  • 20 of 20,000 Aeta highlanders living on volcano killed
  • Monitoring cost - $1.5million, Evacuations - $1.5million (less than expected)
  • Hazard maps underestimated the extent of the hazards – map predicted ash would fall over a 40km radius but it travelled 65km in places.
  • Unfortunate coincidence of Typhoon Yunga – heavy rains increased weight on buildings causing more damage than expected.
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Evaluation of immediate reponse

  • National Disaster Coordinating mobilised to aid the evacuation, rescue and relief response – included providing health and basic education in evacuation centres.
  • Health advisories issued to inform people of how to deal with ash – fine particles of ash could lead to eye irritation or asthma attacks
  • Disease was a major issue in evacuation centres – around 600 of 850 deaths result as disease.  Example – 30,000 people used Amoranto Velodrome, other relocated to shanty towns in cities like Angles – disease spread.
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Evaluation of responce long term

  • System set up to monitor the vibrations of passing lahars and warn of lahars.  This system saves hundreds of lives – warnings enabled to be sounded for most major lahars but not all at Pinatubo 1991
  • Evacuees needed resettled and helped to re-establish their livelihoods.  June 1991 – government set up Task Force Mt Pinatubo – 6-year mandate, 10-billiuon-peso fund.  This was to assist establishment of resettlement centres, provide employment and livelihood opportunities for victims and repair damage to infrastructure  
  • Engineers effort to tap lahars behind levees and dams failed
  • Dozens of people killed by lahars since 1991 – especially on Pasig-Potrero river three major lahars occurred – 1991, 1992 and 19941
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