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Report on Pinatubo (Philippines) — March 1992

Bulletin of the Global Volcanism Network, vol. 17, no. 3 (March 1992)
Managing Editor: Lindsay McClelland.

Pinatubo (Philippines) Lahar triggers secondary explosion on NE flank

Please cite this report as:

Global Volcanism Program, 1992. Report on Pinatubo (Philippines). In: McClelland, L (ed.), Bulletin of the Global Volcanism Network, 17:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199203-273083.

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15.13°N, 120.35°E; summit elev. 1486 m

All times are local (unless otherwise noted)

On 4 April, rainfall triggered a lahar in a NE-flank drainage (Sacobia). The lahar disrupted a portion of the extensive June 1991 pyroclastic-flow deposits, producing a secondary explosion and reportedly a secondary pyroclastic flow. The press described an ash cloud that rose about 1,200 m, and darkened the Angeles area (25 km E of the summit). The lahar also destroyed two sabo dams that were being constructed to reduce future mudflow damage downslope, but no casualties or additional property damage were reported.

Geologic Background. Prior to 1991 Pinatubo volcano was a relatively unknown, heavily forested lava dome complex located 100 km NW of Manila with no records of historical eruptions. The 1991 eruption, one of the world's largest of the 20th century, ejected massive amounts of tephra and produced voluminous pyroclastic flows, forming a small, 2.5-km-wide summit caldera whose floor is now covered by a lake. Caldera formation lowered the height of the summit by more than 300 m. Although the eruption caused hundreds of fatalities and major damage with severe social and economic impact, successful monitoring efforts greatly reduced the number of fatalities. Widespread lahars that redistributed products of the 1991 eruption have continued to cause severe disruption. Previous major eruptive periods, interrupted by lengthy quiescent periods, have produced pyroclastic flows and lahars that were even more extensive than in 1991.

Information Contacts: R. Punongbayan, PHIVOLCS; Reuters.