Mount Pinatubo, Philippines

Basic Facts

Location: It is located on the Philippines, which lies at a convergent plate boundary where the oceanic Philippines plate subducts beneath the continental Eurasian plate.

Date of eruption: 12-15 June 1991

Height of volcano: 1760m

Type of volcano: Composite

Eruption

Mount Pinatubo, which was dormant for six centuries finally erupted on the 12 June 1991. It was a result of the build-up of pressure in the magma chamber as the rising gas-charged magma was blocked by a volcanic plug. When the magma managed to find a way to the surface, the volcanic eruption was violent.

There were signs of unrest wihin the volcano from April. There were steam eruptions, earthquakes and sulphur dioxide emissions. A series of violent explosions occurred from 12 to 15 of June where super heated gas and ash of about 800°C were spewed into the air. There was a lot of dust in the air. Pyroclastic flows sped down the slopes at high speeds. Lahars formed by rain and ash sped down the volcano. There was also a collapse of the magma chamber caused by the withdrawal of magma. These caused earthquakes.

Effects

As the magma chamber had collapsed, a caldera with a diameter of 2 km was formed. Ash was also deposited over large areas, causing pollution and health problems. The lahars, floods and pyroclastic flows dislodged many structures in their way, destroying 42,000 homes, 40, 500 heatares of farmland and infrastructure. 900 lives were also lost from the eruption and its aftereffects such as diseases. However, not many people died because of the early predictions made by the scientists. About 200,000 people were evacuated from the area.

The sulphur dioxide released circled the earth in the atmosphere. Sulphur aerosols were formed when the sulphur dioxide combined with water. This reduced the amount of sunligh reaching the earth, causing a decrease in the average global temperatures. There was also ozone destruction.

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