Mount Pinatubo is an active stratovolcano located on the island of Luzon in the Philippines, at the intersection of the borders of the provinces of Zambales, Tarlac, and Pampanga. Ancestral Pinatubo was a stratovolcano made of andesite and dacite.
TIMELINEÃ¢ÂÂ¢2nd April 1991 - The first steam blasts escape forming a 1.5km line of vents from the summit of Mt Pinatubo. This created a new line of craters, vegetation was killed and several villages were covered in ash.
Ã¢ÂÂ¢3rd April 1991 - Several new vents are formed on the northwest slope, and the Philippine Institute of Volcanology and Seismology (PHIVOLCS) were called in. An aerial survey was directed, but it was decided that this was very minor and that the volcano was letting out steam. 5,000 people were evacuated within a 10km region of the zone.
Ã¢ÂÂ¢5th April 1991 - 40 earthquakes are recorded. A portable monitor was taken into the mountain to measure gas levels of Sulphur Dioxide, and other various volcanic gases.
Also a tiltmeter was installed to measure tectonic activity.
Ã¢ÂÂ¢23rd April 1991 - Earthquakes and steam emissions continue. The U.S Geological Survey Team is called in to help the Philippians. They install 7 seismometers at Clark Air Base. 3 different possibilities are formed to account for the volcanic activity: either excess steam was being released from the volcano and this would have been harmless; or there were temporary tectonic stresses under the crust which would only cause local damage; or there was a possibility that magma from the magma chamber was rising through the volcano which could be catastrophic.
Ã¢ÂÂ¢24th April to 5th June - Small ash explosions are recorded and sulphur dioxide emissions are measured. From now on the alert system is put into operation.
Ã¢ÂÂ¢Over April and May high amounts of Sulphur...