Mount Pinatubo. Image shows the crater after the 1991 eruption. The canal near the bottom of the image was built to release extra water and avoid another round of flash floods. Radiometric dating on Mt. Pinatubo indicates that it has been active for over 1.1 million years. Pinatubo is one of the 22 active volcanoes dotting the Philippines. To the Aetas, the country's semi-nomadic Negrito tribes, Mt. Pinatubo is the Aetas' 'Holy of Holies', the inner sanctum where their supreme God, the Apo na Mallari, dwells. They believe the recent eruption was due to Apo's anger over the continued denudation of the environment.