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Roger Weller, geology instructor
by Sarah Biron
The eruption that rocked a nation.
Imagine, if one day you are sitting home, watching tv, and playing with your family, and the next you are being asked to move out of your house and flee your home, because it was possibly in the way of volcanic ash, debris and lava. This is what happened to many residents of the island of Luzon in the Philippines in 1991.
I have been to the Philippines twice now, and each time when driving to Clark
Air Force Base, the pastor on the church I visit, would tell us what it was like
to be living in the Philippines when this devastation occurred. When driving on
the highway, you can look out the window and still see ash and debris as it has
coated the ground even 20 years later.
How does a volcano just erupt? On July 16, 1990, an earth quake struck the
island of Luzon, creating multiple landslides, and damage to the surrounding
area. This caused the earth to shirt underneath the lying volcano, and random
eruptions of gas and ash would occasionally spew forth from different cracks.
Small earthquakes frequently rocked Luzon.
On April 2nd 1991, the first magma eruption occurred out of the composite
volcano. Since the magma had been seeping gasses on its push upwards towards the
surface, it was not explosive but more like a seeping of magma and fluid. This
continued to happen on and off for the next couple of months. On June 3rd
though, life of the people living on Luzon changed. The first eruption occurred
out of the cone. It created a column of ash 4.5 miles skyward.
People had to be evacuated from a radius of upwards of 27 miles around the
volcano, many Aeta’s (the national inhabitants of the Philippines) who lived on
the volcano fled.
Graphs and instruments began to show that the volcano was actually changing in
size. It was filling with magma, which was creating the cone to grow outward and
to become larger. On June 12th, the beginning of the worst of the
eruptions started to occur. Fifteen minute eruptions sent ash into the air, and
created eruptions clouds almost 15 miles high in the air. Eruptions continued to
occur over the next 24 hours, continually getting worse as time wore on. Another
15 mile high eruption rocked Luzon, with earthquakes and ash and magma being
On June 15th, a typhoon hit the Philippines and made any observation
of the eruptions impossible, but graphs showed that eruptions hit as high as 21
miles skyward. Much of Luzon was covered in Ash, and put into darkness. 50,000
square miles were covered and taken over by the ash the volcano had spewed out.
This volcano was the 2nd largest volcano in the century; it was ten
times stronger than the volcano eruption of Mount St. Helens. Over 800 people
died from the eruption, and too many houses and places of business were
destroyed because of this.
Since the eruption the volcano has remained fairly inactive with random
occasions of spurts and emissions. The caldera on top has now been formed into a
lake, where waters can sometimes reach boiling levels and become acidy.