Pinatubo Eruption - June 1991, Philippines
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On 15 June 1991 at 2:30 local time the largest and most violent of Pinatubo's eruptions began, lasting for 21 hours. The resulting eruption column rose to between 20 and 45 km altitude, causing major ashfall across most of the island of Luzon, and closing Manila International Airport and the US Clark Air Force Base. An already difficult situation was made worse by the simultaneous arrival of Typhoon Yunya. Most fatalities, injuries and damage to property were the result of thick, wet, ash fall causing roof collapse, and lahars causing rivers to overflow and flood huge areas of surrounding land1.
The pre-evacuation of around 250,000 people, saved at least 10,000 lives from pyroclastic flows that covered much of the volcanos flanks, The damage due to heavy ash fall, lahars and resulting flooding was, however, considerable. Worst affected were the provinces of Abra, Benguet, Mt. Province, Ilocos Norte, Ilocos Sud, Bataan, Bulacan, Pampanga, Zambeles, Pangasinan, Tarlac, Cavite, La Union and the National Capital Region1. An estimated 200 million tons of pyroclastic debris was released during the eruption, destroying around 200,000 acres of land2, and covering several communities, including Olangapo and Castillejos, in more than 15 cm of ash3.
Lahars continued to be a serious problem in the vicinity of Pinatubo, for more than a decade after the climactic eruption in June 1991, arising from heavy rains reworking the enormous volume of ash and pyroclastic flow material mantling the volcanos flanks. Typhoon Yunya triggered the initial lahars as the eruption was still in progress, but subsequent, rain-fed, lahars in 10 river courses draining the volcano have caused problems across an area of close to 1,000 km2, particularly at the height of the rainy season, from June to October2,4,5.
The Pinatubo eruption was one of the two largest eruptions of the twentieth century, releasing between 8.4 and 10.4 km³ of tephra6. In addition, the sulphur aerosols injected into the stratosphere by the eruption circumnavigated the planet and resulted in a global average temperature fall of around 0.4 degrees C7.
1 ReliefWeb. 1992. Philippines Mt Pinatubo Volcanic Eruption Aug 1992 UN DHA Situation reports 1-8.
http://www.reliefweb.int/rw/RWB.NSF/db900SID/ACOS-64DEZL?OpenDocument
2 Leung, M.F, Santos, J.R & Haimes, Y.Y. 2003. Risk Modelling, Assessment and Management of Lahar Flow Threat. Risk Analysis. Vol. 23, pp 1323-1335
3 Spence, R.J.S, Kelman, I, Baxter, P.J, Zuccaro, G & Petrazzouli, S. 2005. Residential building and occupant vulnerability to tephra fall. Natural Hazards and Earth System Sciences. Vol. 5, pp 477-494
4 Leone, F & Gaillard, J-C. 1999. Analysis of the institutional and social responses to the eruption and the lahars of Mount Pinatubo volcano from 1991 to 1998 (Central Luzon, Philippines). GeoJournal. Vol. 49, pp 223-238
5 Van Westen, C.J. & Daag, A.S. 2005. Analysing the relation between rainfall characteristics and lahar activity at Mount Pinatubo, Philippines. Earth Surface Processes and Landforms. Vol. 30, pp 1663-1647
6 Dartevelle, S, Ernst, G. G .J, Stix, J & Bernard, A. 2002. Origin of the Mount Pinatubo climatic eruption cloud: Implications for volcanic hazards and atmospheric impacts. Geology. Vol. 30, pp 663-666
7 Lynch, J. 1991. Mount Pinatubo - Explosive Volcanic Eruptions. Weather and Forecasting. Vol. 6, pp 576-580
8 Wikipedia. 2007. Mount Pinatubo
http://en.wikipedia.org/wiki/Mount_Pinatubo
Event overview table
| No. Deaths | 700 |
| No. Injured | 13 |
| No. Affected | 2,100,000 |
| Houses destroyed | 8,000 |
| Houses damaged | 73,000 |
| Other damage |
- Infrastructure |
| Economic cost | $74,200,000 |