8:32:00 a.m. The bulging north flank that geoscientists had watched develop since March is intact. It had clearly grown by 450 feet in some areas, and by late April was estimated to be growing at five feet a day.

8:32:10 a.m. A 5.1 magnitude earthquake about 1 mile beneath the mountain causes the north flank to slide. Tendrils of steam burst from the mountain, releasing pressure bottled up in magma below.

8:33:00 a.m. A cubic mile of mountain gives way, traveling at 70 to 150 mph, and superheated rocks in the volcano's core are suddenly exposed, shooting a lateral blast of gas north, incinerating everything in its path. Huge glaciers on the mountain's peak melt instantly.

8:33:20 a.m. The blast is over but the mountain begins to pulverize as the eruption vents its full fury, sending a thick, 3-mile-wide ash cloud 80,000 feet into the sky.