The Pinatubo eruption of 1991 was one of the largest eruptions the world had seen for some 100 years.

Mount Pinatubo is located on the northern Island of Luzon in the Philippines. It is an active stratovolcano in the Zambales Mountains, NW of Manila. In 1991 the volcano started to show signs of unrest around March and April time. Given all the signs that a very large eruption was imminent, the Philippine Institute of Volcanology and Seismology – assisted by the United States Geological Survey (USGS) – worked to convince local inhabitants of the high severity of the threat, and started evacuating people.
On the 12-15th June 1991 the Volcano suffered major explosive eruptions that reduced the mountains height from 1,745 m (5,725 ft) to 1,485 m (4,872 ft), the eruption was 10 times that of the 1980 Mount St Helens one.

Image Credit: USGS

Image credits: USGS, Alberto Garcia

The volcano was being monitored by volcanologists including a team from the USGS who were working out of the US Clark Air Base, near the volcano. Satellites were also able to collect valuable information about how the ash and gases from the volcano were affecting the atmosphere.

Pinatubo and short term climate change
Tanno and Iguda have found out that the monitoring of the atmosphere after the eruption showed that it lowered the global
average temperatures by 0.5–0.6 °C.

False colour images of aerosol optical depth in the stratosphere, over a period from April 1991 to January 1994. Red colours show the highest values with dark blue showing the lowest. The Pinatubo/Hudson eruptions increased aerosol optical depth in the stratosphere by a factor of 10 to 100 times normal levels. (‘Aerosol optical depth’ is a measure of the prevention of light passing through a column of atmosphere by the presence of airborne particles) (NASA).

Image/video credit: USGS.
for more information check out
NASA Earth System Data Explorer

Where has my mountain gone? Pinatubo before (June 1991) and after (March 1992) from Clark Air Base runway. Image Credit USGS.

This was one BIG eruption!! You can see by these before and after shots taken by the USGS team, just how much of the mountain was blown away.

Close-up view of Pinatubo before and after. Image Credit USGS.

The volcano was so explosive that almost half the mountain was lost during the eruption as you can see from the before and after images of Mount Pinatubo.

After the volcano…

All the loose rock and ash is a major hazard after eruptions. Particularly in tropical areas where it rains a lot. It can get reworked into large mudflows, called ‘lahars’, which travel fast down valleys taking out bridges and buildings.

(Image credit – USGS)

Tanno and Iguda have discovered that the volcano Mount Hudson in Chile erupted explosively close to the time of the Pinatubo eruption. It is thought that the combined effects of these two big eruptions helped to contribute to the short term climate changes that we saw from the NASA data.

The location of Mount (Cerro) Hudson south of Villarrica in Chile.
Image credit: USGS.
Ash plume image from August 1991 of the Mount Hudson eruption. Image Credit: NASA


Make a science poster about volcanic hazards. Using your knowledge gained from the Pinatubo and Mount St Helens, make up a poster that covers aspects of volcano hazards.

  • You can design your poster on the computer or simply by using a set of pages stuck onto a larger page or piece of card.
  • one cool and easy way is to mix computer printed out pages (e.g. pictures and text) with your own pages. You can also link between pictures and pages with coloured string.
  • Remember to make your poster clear and simple enough for people to follow… what’s the title of yours going to be?

You can make your poster as colourful and interactive as you want – maybe, you could put flaps on it that reveal facts. Science posters are often presented at conferences to show some research and topics that scientists have been working on.

Dr V presenting a poster about his ‘Victor the Volcano’ book at a conference in Dublin, Ireland.

You can go to the previous Volcanoes secret pages by clicking the places below.

StromboliVesuvius/PompeiiErta Ale
Mount St HelensSarychevMount Fuji