Mount Pinatubo is an active stratovolcano located on the island of Luzon, at the intersections of the borders of the Philippines provinces of Zambales, Tarlac and Pampanga. It is located in the Cabusilan Mountain range separating the west coast of Luzon from the central plains, and is 42km (26mi) west of the dormant and more prominent Mount Arayat, occasionally mistaken for Pinatubo. 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 during the protracted Spanish conquest of the Philippines which first commenced in 1565. The volcano’s ultra-Plinian eruption in June 1991 produced the second largest terrestrial eruption of the 20th century (after the 1912 eruption of Novarupta and the largest eruption in the living memory. The colossal 1991 eruption had a Volcanic Exclusivity Index (VEI) of 6, and came some 450-500 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 1000 years after previous VEI 6 eruptive activity. Successful predictions of the onset of the climatic eruption led to the evacuation of ten 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.
The effects of the eruption were felt worldwide. It ejected roughly 10 billions metric tones (10 cubic km) of magma, and 20 millions 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 Krakotoa in 1883. Over the following months, the aerosols formed a global layer of sulfuric acid haze. Global temperatures dropped by about 0.5 0C (0.9 0F), and ozone depletion temporarily increased substantially.
There was no fire from the mouth of Mt. Pinatubo when it erupted on June15, 1991 but its searing heat turned many surrounding areas into a lake of hell. The pyroclastic flow at 1000 degrees Celsius instantly devoured people. The ash fall buried houses and families. Lahar, a steaming mudflow that cascaded from the mountains with the monsoon rains, buried many towns from Mt. Pinatubo; many said they heard the horrifying sound of a thousand stampeding carabaos. The deadly and monstrous volcanic eruption is up in the air. In its first major eruption on June 15, Pinatubo fills the sky with a swelling ash cloud as high as 15000 to 25000 meters and as wide as 15 to 18 kms. The eruption is sustained from five until eight in the morning, turning day into night. Winds from typhoon Yunya carry the volcanic dust to Manila and across the seas.
In June 1991, the world became acquainted with the fury of Mt. Pinatubo. Considered to be the one of the worst volcanic eruptions in the history, the believed-to-be-dormant volcano unleashed millions of tons of sulfur dioxide gas and caused devastation to the thousands of people, with ashes reaching as far, as Antarctica. But don’t you know that before the eruption, Mt. Pinatubo was the home of hundreds of Aetas in Zambales? The Aetas believed that the volcano erupted because its peace was disrupted. Their ancestors had told them about a great tragedy that befell the province when the mountain was disturbed hundreds of years ago. Whether the eruption was a natural or supernatural occurrence, Mt. Pinatubo has made a mark in history and has become a destination worth visiting.