VANCOUVER, Wash. -- Visitors to Mount St. Helens observed a moment of silence at 8:32 Wednesday morning to mark the time 25 years ago when the volcano erupted.

MOUNT ST. HELENS Video: Time-Lapse Of Dome’s Growth Video: Time-Lapse Of Fin Growth Video: Thermal Imaging Of Rock Avalanche Slideshow: Hulking Rock Slab Grows In Volcano's Crater Slideshow: Images From 3-8-05 Ash Plume Slideshow: Infrared Shots Of Activity At Mount St. Helens Slideshow: Dome In Mount St. Helens Crumbling Slideshow: Glowing Lava Oozes From Crater Slideshow: Large Plume Drifting North-Northeast Slideshow: Steam Eruption On 10-4 Slideshow: User Submitted Mount St. Helens Images Slideshow: Steam Vent Forms After Eruption Images: Mount St. Helens Gets Steamed Slideshow: Steam Shoots From Crater Webcam: Mount St. Helens VolcanoCam Complete Coverage Of Mount St. Helens

The blast killed 57 people, leveled hundreds of square miles of forest and dumped gritty ash across Washington. It sent mudflows down the Toutle River that clogged the Columbia.

One of those killed was a U.S. Geological Survey scientist named David Johnston. He was monitoring the volcano from a ridge five miles away and just had time to radio his office and shout, "Vancouver! Vancouver! This is it!"

Anyone visiting the mountain Wednesday needed rain gear as clouds obscured a view of the mountain.

Events 1980 - 2005 Eruption 25th Anniversary

The mountain rumbled back to life last September with shuddering seismic activity that peaked above magnitude three as hot magma broke through rocks in its path.

Molten rock reached the surface in October. In March, it shot ash higher than 30,000 feet.

But since then, the volcano has maintained low-key activity, with wispy smoke regularly floating from the crater.