Pinatubo rose about 5725 ft ( 1745 m) above sea level before the June 1991  eruption. This means almost 500 ft (150 m) of the volcano was blasted away by  this eruption. This seems to be the history of the volcano. After a relatively  short explosive eruption, it will undergo a period of slow growth through  extrusions. Then the volcano becomes dormant for a longer period, and much of  the material deposited during the last eruption is eroded. Finally, another  explosive eruption will occur and destroy whats left of the growth from the last  eruptive period. This process seems to have repeated itself over time, creating  a somewhat stable size for the volcano.

The largest eruption in the history of the modern Pinatubo occurred over  35,000 years ago. This eruption distributed over 325 ft (100 m) of pyroclastic  flow material on all sides of the volcano. It also marked the birth of the  modern volcano. The magnitudes of eruptions since that event are decreasing with  time.

This photo  depicts a secondary eruption on Mt. Pinatubo in May 1994.
This eruption  lasted about four hours. Copyrighted photo by Marko Riikonen.

Pinatubo typically erupts large quantities of relatively cool ash and dacite  magma. It follows that a large, shallow magma chamber exists beneath the  volcano. When gas and crystal rich magma evolves in this chamber, explosive  eruptions occur. There is great evidence of mafic magma  mixing with the dacitic magma in these chambers causing these eruptions.

Pinatubo has been relatively quiet since the 1991-1992 eruption, but it is  still active. It remains to be determined whether or not more explosions at the  volcano are likely during the current eruptive period.

This photo shows  a view of Mt. Pinatubo looking northeast at sunrise.
Copyrighted photo by  Marko Riikonen.

• The Sleeping Giant Awakens

"Fire and Mud: Eruption and Lahars of Mount Pinatubo,  Philippines"

Newhall, Christopher G. and Punongbayan, Raymundo S., Fire and Mud: Eruptions  and Lahars of Mount Pinatubo, Philippines, Philippine Institute of Volcanology  and Seismology, Quezon City and University of Washington Press, Seattle and  London, 1126 pages, 1996.

Clark Airbase, versinkt in Asche

Kurze Zeit vor dem großen Ausbruch 1991. Galt bis zu diesem Zeitpunkt als “ruhender” Vulkan.

Volcano Map

This photo shows  Mt. Pinatubo looking northeast. Copyrighted photo by Marko Riikonen.
Pinatubo is a stratovolcano on the island of Luzon. Its eruptive history is divided into two distinct parts.  The first part of this history involves an ancestral volcano to Pinatubo. This  period includes all eruptions to about 35 thousand years ago. Ancestral Pinatubo  was a stratovolcano made of andesite and dacite.  There is no evidence of large explosive eruptions from this volcano. Ancestral  Pinatubo was centered where the modern Pinatubo currently stands. It may have  risen as high as 7550 ft (2300 m) above sea level at one time. Remains of a 2.2  by 2.8 mile (3.5 by 4.5 km) wide caldera from the old Pinatubo are still standing in the area today.

Several of the surrounding volcanoes were actually vents of the ancestral  Pinatubo. These include the Mt. Negron dome, the Mt. Cuardrado dome, the Mataba  dome and Bituin plug, and the Tapungho plug.

The modern Pinatubo is a dome complex and stratovolcano made of dacite and  andesite. This complex is surrounded by pyroclastic flow and lahar deposits from large explosive eruptions. These explosive eruptions have been  clustered into 6-12 eruptive periods. The explosive eruption of June  15, 1991 is one of the smallest of these eruptive periods. The 500 year  period of dormancy that preceded this eruption was actually relatively short  compared to other such periods in the history of the volcano.

This photo shows a collapsed eruption cloud at the end of a secondary  eruption in May 1994. The cloud is moving towards the camera.

Copyrighted photo  by Marko Riikonen.