The Eruption of Mount Pinatubo - Case Study - Geography

The Eruption of Mount Pinatubo On the 15th June of 1991, the second largest volcanic eruption of the twentieth century took place on the island of Luzon in the Philippines, 90 km northwest of the capital city Manila. It was also, by far, the largest eruption to affect a densely populated area. Mount Pinatubo, a stratovolcano, is part of a chain of volcanoes along the Luzon arc on the west coast (refer map). The arc of volcanoes is due to the subduction of the Manila trench to the west. The mountain has a very huge eruptive history. It was known to be thermally active and had been explored as possible geothermal energy resource by the Philippine National Oil Company. Mount Pinatubo is among the highest peaks in west-central Luzon. Its†¦show more content†¦And a level 5 alert triggered evacuation of the 20Ââ€"40 km zone on the 14th of June. For the people who werent willing to leave the area, a video showing the extreme hazards of the eruption was played to convince them of the dangers of the eruption. Als o, on the 10th of June, the military finally issued evacuation orders and the 18,000 Clark Air Base personnel along with their families were transported to Subic Bay Naval Station (most were returned to the US). In total, the authorities were able to evacuate 200,000 people. From June 7 to 12, SO2 gas emissions, which had increased tenfold from May 13 to May 28, suddenly decreased. The US government wanted definite answers so the USGS geologists went to the site to look for evidence. They monitored the SO2 emissions for two weeks and the results indicated that either the volcano had postponed its attack or that the chamber was blocked and the magma was pressurizing within the volcano. The Eruption On the 12th of June (Philippine Independence Day), millions of cubic yards of gas-charged magma reached the surface and resulted in the first major eruption which was then followed by a series of eruptions. It produced a 19 km long ash column and pyroclastic flows that extended up to four km from the summit to the river valleys. Later, a 15 minute eruption hurled ash straight up to the sky, reaching the heights of 24 km. The super heated air and the friction between