June 7, 1991: Mt. Pinatubo Explosion Initiates Massive Eruption

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A Brief History

On June 7, 1991, a sleepy volcano on the Philippine island of Luzon experienced an explosion that sent an ash cloud 4.3 miles high.  After months of activity indicating an eruption was imminent, the first eruption started on June 3, but the first big explosion with magma flow happened on June 7.

Digging Deeper

By this time, authorities had been evacuating the population for several miles around the volcano, increasing the area evacuated twice to a radius of about 25 miles.  Many residents had started leaving of their own accord prior to official evacuations.  (About 350,000 people lived in the evacuation zone.)

Over a 12 day period from June 3 to June 15, 1991 a series of eruptions emitted incredible amounts of lava and ash.  At least 847 people were killed outright by being buried in ash and mud made from ash and torrential rain. (Cracked fact: Typhoon in progress!)  Many more may have died indirectly from the absence of medical facilities that were buried or the inability to travel to medical facilities.

This eruption was the second largest during the 20th Century, exceeded only by Alaska’s Novarupta eruption in 1912 (with so few people around, little damage was done).  Pinatubo’s eruption was about 10 times that of Mt. St. Helens!  Almost all of Luzon was covered in volcanic sludge.  The recently evacuated Clark Air Base (USAF) was buried in ash as was Subic Bay (USN) Naval Base.

Perhaps cold statistics will illustrate the scale of this eruption:  11 billion tons of magma (lava) ejected, 22 million tons of sulfur dioxide, 880 tons of mercury, 1100 tons of cadmium, 610,000 tons of chromium, 11,000 tons of arsenic, 110,000 tons of lead, 220,000 tons of nickel, and 880,000 tons of zinc.  Pinatubo spewed more ash than any eruption since Krakatoa in 1883, enough to drop world temperatures by almost 1 degree F.

A map of Krakatoa after the 1883 eruption, showing the change in geography.

Prior to the 1991 activity Pinatubo had been dormant for hundreds of years.  Covered by trees and jungle, the volcano was hidden and pretty much forgotten.  This incident stands as a terrifying reminder that this could happen in the US or Europe, or anywhere volcanic activity takes place. 

Dormant volcanoes are not dead, they are just sleeping.  Where do you think the next big one will hit?

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Historical Evidence

For more information, please see…

Rantucci, Giovanni.  Geological Disasters in the Philippines: The July 1990 Earthquake and the 1991 Eruption of Mount Pinatubo.  CreateSpace Independent Publishing Platform, 2012.


About Author

Major Dan

Major Dan is a retired veteran of the United States Marine Corps. He served during the Cold War and has traveled to many countries around the world. Prior to his military service, he graduated from Cleveland State University, having majored in sociology. Following his military service, he worked as a police officer eventually earning the rank of captain prior to his retirement.