Type of Volcano

Mt. Pinatubo is one of a chain of composite volcanoes that constitute the Luzon volcanic arc. The arc parallels the west coast of Luzon and reflects eastward dipping subduction along the Manila trench to the west. Mount Pinatubo is one of the highest peaks in west-central Luzon. Mt. Pinatubo is on the Philippines plate which is composed of oceanic crust.

Geologic Location

Mt. Pinatubo is in the Country of The Philippines, In the City of Luzon. Located at 15.13N, 120.35E, with an Elevation of 5248 ft (1600 m). Umingan, San Jose City, and Aritao are some nearby cities to the city of Luzon, where Mt. Pinatubo is located. Pinatubo lies at a desctuctive plate boundary between the Philippine and the Eurasian plate. The picture above shows the type of plate boundary in which Mt. Pinatubo is on.

Eruption History

Mount Pinatubo's most recent and most famous eruption was on June 15, 1991 (pictured above). It was the second-largest volcanic eruption of this century and the largest eruption to affect a densely populated area.The eruption produced high-speed avalanches of hot ash and gas, with giant mudflows, and released over 5 billion cubic meters of of volcanic ash and other pyroclastic material into the environment hundreds of miles across. The eruption took the lives of 500 people and took billions of dollars to repair. The impacts of the eruption continue to this day. There have been some sources that say there have been follow up, secondary eruptions in the later years of 1993 and 1994.

Volcano Shape

Mt. Pinatubo is located at 15.13N, 120.35E.
Its elevation is 5248 ft (1600 m)

The birth of now-a-days Pinatubo occurred in the most explosive eruption in its history, which deposited pyroclastic flow material up to 100 meters thick on all sides of the mountain. The total volume of material erupted may have been up to 25 cubic kilometers , and the removal of this amount of material from the underlying magma chamber led to the formation of a large caldera.  Pinatubo is a stratovolcano,which are also called composite volcanoes. They are tall, conical volcanos with many layers of hardened lava and volcanic ash. Stratovolcanoes have steep profiles and periodic, explosive eruptions. The lava that flows from it tends to be viscous; it cools and hardens before spreading far. The magma forming this lava is often felsic, having high-to-intermediate levels of silica , with less amounts of less-viscous mafic magma.  Several mountains near Pinatubo are old satellite vents of olden days Pinatubo, formed from volcanic plugs and lava domes. Some nearby peaks are also remains of old Pinatubo, formed from erosion-resistant parts of the old mountain slopes left behind when the less resistant parts were eroded away by weathering.

Neighboring Volcanoes

none

Eruption Style

Mt. Pinatubo is an Explosive volcano. It emmitts andesitic lava. When it is erupted it has very dangerous pyroclastic flows, due to its high viscosity. Before the eruption in 1991 there were several important river systems throughout Mt. Pinatubo. They were large and important ecosystems. After the eruption deep valleys were filled with pyroclastic deposits. The rivers have been clogged with sediment and the valleys have been faced with frequent lahars.

Enviornmental Dangers/Benefits

The surrounding flatter areas, of Mt. Pinatubo, has an abundant rainfall of almost 4 meters annually, provided by the monsoon, climate and the fertile volcanic soils provide excellent conditions for agriculture. After the eruption of 1991, there were large amouts of severe damage, communities, buildings, and roads. Houses were either damaged or destroyed. The roads were destroyed by pyroclastic flows and lahars. The cost of repairing the damage from the 1991 eruption was 3.8 billion pesos. Pinatubo has a very large amount of lava and ash that is ejected when it erupts, Mass amouts of aerosols and dust are projected into the stratosphere. Also Sulfur dioxide oxidised in the atmosphere to produce an array of sulfuric acid droplets, which slowly spread throughout the atmosphere, post eruption.

Bibliography

Plate Tectonics. 30 Mar. 2009 http://www.goffs.herts.sch.uk/website/humlinks/geog3/ RevisionGuidePlateTectonics.htm.


United States. Cong. Mount Pinatubo, Philippines Photo Archives. By Lyn Topinka. Ed. Lyn Topinka.
USGS. 20 Aug. 2008. 23 Mar. 2009 .



Riikonen, Marko. Mt. Pinatubo. Mt. Pinatubo. "Mt. Pinatubo Volcano, Phillipines." Malapascua Island . 23 Mar. 2009 http://www.malapascua.de/Volcanoe-Map/Pinatubo__Philippines/%20.


Encyclopedia of Earthquakes and Volcanoes
By David Ritchie & Alexander E. Gates PH.D.
Pages 177-178

For more information on Mt. Pinatubo you can visit
http://www.teachersdomain.org/resource/ess05.sci.ess.earthsys.lahar/
or watch a video of The 1991 Eruption at
http://videos.howstuffworks.com/discovery/7169-1991-mount-pinatubo-erruption-video.htm