Mount Pinatubo Eruption 1991
Location: Mount Pinatubo is an active stratovolcano located on the island of Luzon, near the tripoint of the Philippine provinces in South East Asia. It is located in the Cabusilan Mountains separating the west coast of Luzon from the central plains. It is located at the plate boundary between to the Eurasian and Philippine Plate. It is one of a chain of volcanoes known as the Luzon volcanic arc.
* 15th march- earthquakes felt by villagers on the north western side of the volcano. Earthquake of increasing intensity for the next two weeks.
* 2nd April – phreatic eruptions along a 1.5km fissure on the summit.
* Small eruptions of gas over next few weeks
* 3rd May – first eruption of magma.
* 7th June- Large explosion generated an ash column 7km high
* 12th June – more violent eruptions with small earthquakes producing ash columns 24km high
* 15th June – ash was ejected 34km into the atmosphere. Pyroclastic flows travelled up to a 16km and the ash mixed with rain from typhoon Yunya creating lahars. The eruption lasted 3 hours.
Cause of the Eruption
The eruption was a result of the Oceanic Philippine plate being subducted under the lighter Continental Eurasian plate. The volcano is slightly offset from the plate boundary as, when the Oceanic plate is subducted it is melted and forced away as molten magma by the high pressures exerted on it. It then resurfaces as the density of the molten magma becomes lower than that of the rock, and so it pushes it up through the small cracks and explodes out through a volcano.
Effects of the Eruption
The eruption caused sulphur dioxide and ash particles to be ejected into the atmosphere. This resulted in less infrared radiation entering the atmosphere and more heat being absorbed rather than being reflected back to the Earth. This led to global cooling. Temperature levels didn't return to normal until 1994.