Mount Pinatubo is a 5771 foot (1699 meter) active
stratovolcano located on the central island of Luzon in the
Philippines, about 55 miles northwest of Manila. Pinatubo is one of 22 volcanos in the Zambales Range which extends north-northwest from Bataan to the Lingayen Gulf. The volcano stradles the
provinces of Pampanga, Zambales, and Tarlac.
Pinatubo was consistently
active (and sometimes exceedingly
violent) over the course of the past million years. The most
extensive eruption was about 35,000 years ago when a
pyroclastic flow left over 350 feet of ash and
debris on all sides of the mountain. The last activity occured over 500 years ago and volcano had been considered
dormant since.
The
volcano awakened after a 500 year
sleep when
steam venting was seen on April 2, 1991. This led to the
installation of
temporary seismic activity monitoring stations (by the cooperation of PHILVOLCS and the U.S.
Air Force), which recorded as much as 178 seismic events per day. In June, the activity jumped to between 1500 and 2000 events per day and ash began to be
ejected. The first major explosion came on at 8:51 am June 12 when seismic activity was followed by three
explosions which produced an ash
cloud that reached 20 miles into the sky. Explosions continued through June 15
1991 when it buried over 310
2 miles (800
2 km) with over 2
3 miles (8
3km) of ash (the cloud rached a height of 30 miles). surrounding the volcano, the ash was over 10 feet (3 meters) deep. heavy
monsoon season rains turned the deep ash into mudflows (
lahars). fortunately, the digilence of local PHILVOLCS officials and
United States military personnel at Clark Air Force Base, 55,000 individuals were
evacuated before the eruption.
Though the eruption of Pinatubo has been considered one of the
worst volcanic eruptions of the 20th
century, this eruption was relatively
minor in comparison to its
history.
The volcano has been fairly
quiet since its reawakening, erupting a few times (minor in comparison to the 1991 eruption) from
1991 through
1994. These eruptions have consisted primarily of large eruptions of cool ash.
Pinatubo also serves as a
holy place for the Aetas, a semi-
nomadic tribe who believe they can
communicate with the
spirits of their
ancestors whose
souls (they believe) now inhabit
animals,
trees, and
mountains. They believe that their
supreme god, Apo na Mallari, lives inside Pinatubo.