Field of Science

15, June 1991 : The Pinatubo eruption climax

Pinatubo (Philippines) was, despite some activity of fumaroles, not considered an active or dangerous volcano.
il 2, 1991 an initial explosive eruption phase occurred on a 1,5 kilometre long fissure, until June 8, the eruption changed to a more effusive type with a climax June 15, when the eruption plume reached a height of 20.000 meter. Subsequent research showed that deposits of pyroclastic flows and lahars can be found up to 20 kilometres distant to the mountain. These deposits were dated to approximately 5.100-4.400, 3.000 to 2.300 and 600-400 years, the entire volcanic edifice of Pinatubo and its base is dated at least to 1,1 million years.
Historical eruptions were however not known; a possible event in the year 1531 or 1561 is assumed but not confirmed by accounts or local stories - the slopes of the mountains were also for centuries occupied by the local tribe of the Aetas.

Despite the intensity of the eruption, only estimated 700 to 1.000 victims were count. The evacuation zone around the volcano was increased from 20 to 30 kilometres, pyroclastic flows were observed up to a distance of 14 kilometres; more dangerous were lahars that endangered places up to 50 kilometres distant. The eruption of Pinatubo lasted until September 1991, it formed a 2 kilometre large caldera and lowered the mountain by 100 meter.
Notable was the influence of aerosols and sulfur dioxide of the eruption plume on the worldwide climate -these components are thought to have cooled the global temperature by 0.25°C.

Online Resources:

KLEMETTI, E. (15.06.2011): The 20th anniversary of the eruption of Pinatubo in the Philippines. (Accessed 15.06.2011)

Cover picture from USGS (1991): Vertical eruption at Pinatubo, 1991. (Accessed 15.06.2011)


  1. D'oh! Pinatubo is in the Philippines, not Indonesia.

  2. Indeed -that´s a Homer, thanks for the fast tweet!

  3. The Pinatubo sunsets lasted for about a year and a half.


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