The Pinatubo

The 1991 eruption and 'the day after'

Top of the Pinatubo

A enormous depression (Caldera)

was the result of the explosion

Some months before the ultimate explosion...

More than two months before the big explosion, the first signs of activity in the volcanic area of the Pinatubo started. After a first explosion clouds of steam  and ash ejections came out of  the flanks of the volcano. An area of about 10.000 m² was covered by the ash. Soon new gas plumes came out of  six main vents in the volcano. The frequency of earthquakes, explosions and plumes, increased more and more. Most days earthquakes had a high-frequency of  more than 50 in 24 hours!

The Day... 

After  more than two months the activity of the earth culminated in the largest explosion. It became one of the largest eruptions of the past century. The heaviest eruption  lasted for more than 15 hours, with tremendous explosions and huge ejections of gas, ash and pyroclastic flows. Many times  ash was thrown up to more than 20 km altitude, one time even more than 35 kilometer altitude. Most of the ash felt to the south-east, south and south-west of the Pinatubo. At the island of Palawan, on a distance of 500 km  from the

Pinatubo, ash, carried by  typhoon winds, felt down.  Clouds of ash darkened Manila. Manila's international and domestic airports had to be closed for several days!

Within several days...

Earthquake-frequency increased in several days to 1000 - 2000 earthquakes in 24 hours. All the people within 21 km from the summit of the Pinatubo were ordered to evacuate. Near the main vent a huge lava dome was created of 100 x 60 meters and 30 meters high. Within a week after the big explosion the evacuation of the U.S. Clark Air Base (more than 15 km east of the Pinatubo) was ordered. The danger of the coming volcanic flows into the direction of Clark Air Base was to big. 

Less then ten days later...

Eight days after the big explosion of the Pinatubo, the huge ash cloud, of which the main body was 11000 km long, reached central Africa. More than a month later, the volcano was still emitting ash, which reached altitudes of 3 - 6 km, occasional pulses to 15 - 16 km

The changing face of the Pinatubo

The big explosion had tremendous effects for the volcano landscape. The summit of the volcano was for a large part removed by the explosions and by collapsing into the  crater area. A large hole, a caldera, of 2-3 km in diameter was the result. The new summit of the volcano was 145 meters lower than before the explosion.  

Picture left: The ash cloud, eight days after

                  the big eruption of 1991

 Map of the 1991-95 lahars at Pinatubo. Courtesy of PHIVOLCS