"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 from 1745 to 1486 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. At least six major eruptive periods, interrupted by lengthy quiescent periods, have occurred from modern Pinatubo volcano during the past 35,000 years. Most of these have produced major pyroclastic flows and lahars that were even more extensive than in 1991."  -Smithsonian Volcano Archive
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