Mount Pinatubo

Pinatubo Volcano

Mount Pinatubo is located about 100 km northwest of Manila on the west coast of the island Luzon as part of the Luzon volcanic arc . The volcano consists of steep , deeply dissected upland slopes bounded by coalescing low gradient alluvial fans built from products of previous eruptions (Hayes et al , 2002 . The explosive eruption of mount Pinatubo in 1991 belongs to the third volcanogenic environment . The volcano is located between the Manila trench and Phillippines fault (about 90 km west of it ) which erupted in 1990 . the Luzon earthquake was indirectly

br responsible for the awakening of the dormant Pinatubo , the actual triggering factor of the June 12 , 1991 eruption was the subsurface block rearrangement which started after 1990 quake and went on for months . The long reassemblage stage which took place after the aftershock period modified the pre-existing equilibrium and affected the rock basement of the central valley , thus favoring magmatic injections into the mount Pinatubo chamber and the consequent awakening of the volcano (Rantucci br

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The 1991 eruption of the Pinatubo in the Phillippines was an plinian eruption . This type of eruption is triggered by rapid formation of gas rich pasty lava with a high water , high silica content magma , deep down inside an eruption vent . With the vent serving as a gun barrel pyroclastic fragments are jetted out vertically and with such tremendous force that eruption columns , 30 km tall or higher , are commonly produced . Paricles of various sizes , from fine ash to volcanic bombs are ejected with such violent force that pumice fragments , as big as hen 's eggs ' may fall as far as 15 km from the crater , and volcano ash may form a 1 cm thick deposits at sites , hundreds of km from the volcano (Stoltman et al , 1991 ,

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Pinatubo volcano can be classified as the stratovolcano or composite volcano type . One of the most common and deadly hazard at most strato volcanoes is called a Lahar . Any mudflow in a volcano can termed as Lahar . Lahars can be devastating because they move quickly , and often a small eruption or relatively small rainstorm can generate a huge Lahar The 1991 Pinatubo eruption deposited a huge volume of relatively loose pyroclastic material on already steep and gullied slopes . Additionally the rainfall in the Philippines is very high . The combination of all this unconsolidated material and heavy rainfall has generated hundreds of lahars , some of which have been enormous .1

The eruption of Mount Pinatubo deposited 5-6 km3 of pyriclastic material on the flanks on the volcano , filling adjacent river valley with up to 200 m of volcanic debris . Within 3 years , rapid river incision had transported a third of the volcanogenic sediment downstream , depositing it on densely populated alluvial fans (Hayes et al , 2002 . The Pinatubo Volcanic Observatory (PVO ) team undertook a rapid geologic reconnaissance to determine the style and extent of past eruptions and to provide the basis for a volcano-hazard map . This reconnaissance showed that activity at Mount Pinatubo...