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 3102 miles (8002 km) with over 23 miles (83km) 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.