Mount Pinatubo is an active
stratovolcano located on the island of
Luzon in the
Philippines, at the intersection of the borders of the provinces of
Zambales,
Tarlac, and
Pampanga. Ancestral Pinatubo was a stratovolcano made of
andesite and
dacite. Before 1991, the mountain was inconspicuous and heavily
eroded. It was covered in dense
forest which supported a population of several thousand indigenous people, the
Aeta, who had fled to the mountains from the lowlands when the
Spanish conquered the Philippines in 1565.
The volcano's eruption in June 1991 produced the second largest terrestrial eruption of the 20th century.[3] The 1991 eruption had a Volcanic Explosivity Index (VEI) of 6, and came some 450-500&_160;years after the volcano's last known eruptive activity (estimated as VEI 5, the level of the 1980 eruption of Mount St. Helens), and some 500-1000&_160;years after previous VEI 6 eruptive activity.[4] Successful predictions of the onset of the climactic eruption led to the evacuation of tens of thousands of people from the surrounding areas, saving many lives, but surrounding areas were severely damaged by pyroclastic flows, ash deposits, and later by lahars caused by rainwater remobilizing earlier volcanic deposits thousands of houses and other buildings were destroyed.[3]
The effects of the eruption were felt worldwide. It ejected roughly 10&_160;billion metric tons of magma, and 20&_160;million tons of SO2, bringing vast quantities of minerals and metals to the surface environment. It injected large amounts of aerosols into the stratosphere—more than any eruption since that of Krakatoa in 1883. Over the following months, the aerosols formed a global layer of sulfuric acid haze. Global temperatures dropped by about 0.5&_160;°C (0.9&_160;°F), and ozone depletion temporarily increased substantially.
Pinatubo is part of a chain of volcanoes which lie along the western edge of the island of Luzon. They are subduction volcanoes, formed by the Philippine Plate sliding under the Eurasian Plate along the Manila Trench to the west. Mount Pinatubo lies on a destructive plate boundary.The word 'pinatubo' means 'to have made grow' in Tagalog and Sambal [5], which may suggest a knowledge of its previous eruption in about AD&_160;1500, although there is no oral tradition among local people of earlier large eruptions. Pinatubo might instead mean a fertile place where crops can be made to grow.
