Operation Fiery Vigil - Timeline of Events

Timeline of Events

• 16 July 1990: a magnitude 7.8 earthquake struck the island of Luzon, Philippines. The epicenter was near the town of Rizal, Nueva Ecija, roughly 60 kilometers from Mount Pinatubo. This earthquake caused a landslide, some local tremors, and a brief increase in steam emissions from a preexisting geothermal area at Mount Pinatubo.
• March–early June 1991: magma rising toward the surface from more than 32 kilometers beneath Mount Pinatubo triggered small earthquakes and caused powerful steam explosions that blasted three craters on the north flank of the volcano. Thousands of small earthquakes occurred beneath Pinatubo, and many thousands of tons of sulfur dioxide gas were emitted by the volcano.
• 7 June 1991: the first magmatic eruptions took place, resulting in the formation of a 660 feet (200 m) high lava dome at the summit of the volcano.
• 10 June 1991: after receiving final authorization from the Secretary of Defense, all non-essential military and Department of Defense civilian personnel and their dependents initiated land evacuation from Clark Air Base at 0600 local time. This land evacuation brought an estimated 15,000 personnel and several thousand vehicles onto U.S. Naval Base Subic Bay.
• 12–14 June 1991: several waves of eruptions generated eruption columns up to 80,000 feet (24,000 m) in altitude and pyroclastic flows (high speed avalanches of superheated gas and tephra) extending out to 4 kilometers from the summit. These eruptions were accompanied by nearly continuous seismic activity and expulsion of huge quantities of ash, tephra, and volcanic bombs.
• 15 June 1991: the major eruption of Mount Pinatubo occurred, sending ash and tephra over 100,000 feet (30,000 m) into the air. Clark Air Base and Subic Bay Naval Station, the two largest U.S. military bases in the Philippines, were heavily damaged by ash from this volcanic eruption. Nearly one foot of ash accumulated on both Clark Air Base and U.S. Naval Base Subic Bay. Many buildings collapsed under the weight of the accumulated ash, and all flight operations were suspended at both bases for many days or even weeks afterwards.