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.
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.