Operation Fiery Vigil was the emergency evacuation of all non-essential military and U.S. Department of Defense civilian personnel and their dependents from Clark Air Base and U.S.

The eruption produced high-speed pyroclastic flows, giant lahars, and a cloud of volcanic ash hundreds of miles across.

[2] Twenty million tons of sulfur dioxide[3] and roughly 11 cubic kilometers (2.6 cu mi) of tephra[4][5] are estimated to have been ejected in total, which corresponds to a Volcanic Explosivity Index of 6.

[6] By contrast, roughly four cubic kilometres (0.96 cu mi) of material was ejected in the 1980 eruption of Mount St. Helens; this corresponds to a VEI of 5.

The vast majority were evacuated to Andersen Air Force Base, Guam and processed for return to the continental United States.