Pinatubo, Mount (pĭn'əto͞o`bō), active volcano, 5,840 ft (1,780 m), central Luzon island, the Philippines, c.55 mi (90 km) NW of Manila. Dormant for 600 years, it began erupting on Apr. 2, 1991. Most residents had evacuated surrounding areas when Pinatubo erupted catastrophically (June 15, 1991), killing over 500 people and burying over 310 sq mi (800 sq km) under volcanic ash. As much as 2 cu mi (8 cu km) of ash was ejected in the eruption. The nearby U.S. Clark Air Force Base was devastated by the ash fall, which resulted in the base's closure. Landslides of rain-soaked volcanic ash caused further destruction in 1991 and subsequent years.