Mount Pinatubo is an active stratovolcano in the Zambales Mountains, located on the tripoint boundary of the Philippine provinces of Zambales, Tarlac and Pampanga, all in Central Luzon on the northern island of Luzon. Its eruptive history was unknown to most before the pre-eruption volcanic activities of 1991, just before June. Pinatubo was heavily eroded, inconspicuous and obscured from view. It was covered with dense forests which supported a population of several thousand indigenous Aetas.
Pinatubo is most notorious for its Volcanic Explosivity Index 6 eruption on June 15, 1991, the second-largest terrestrial eruption of the 20th century after the 1912 eruption of Novarupta in Alaska.