Mount St. Helens erupted on May 18, 1980. The volcano, located in southwestern Washington, used to be a beautiful symmetrical cone about 9,600 feet (3,000 meters) above sea level.

Header Image Credit - By Gregg M. Erickson (talk · contribs) - Own work, CC BY 3.0,

Mt. St. Helens Changed Our World.

Mt. St. Helens Eruption 41st Anniversary

Mount St. Helens erupted on May 18, 1980 at 8:32am

Vancouver! Vancouver! This is it!

On March 1, 1980, a new system of seismographs at the University of Washington went into operation to monitor earthquake activity in the Cascades. On March 20, it recorded a magnitude-4.2 earthquake deep beneath Mount St. Helens, inaugurating a round-the-clock watch that was to save many lives. From March 25 to March 27, quakes of magnitude 4.0 rocked the mountain as many as three times a day, and smaller quakes occurred several times every hour.

At 8 a.m. PST on March 27, the U.S. Geological Survey issued an official Hazard Watch for Mount St. Helens; around noon, the first eruption of steam from the summit sent a column of ash and steam 6,000 feet (1,829 meters) into the air. Twin fissures opened on the mountain’s north face.

On the morning of May 18, USGS volcanologist David A. Johnston, camped on the ridge with his lasers, radioed in his regular 7 a.m. report. The changes to the bulging mountain were consistent with what had been reported several times daily since the watch began. At 8:32, a magnitude-5.1 earthquake registered on the seismographic equipment. His excited radio message, “This is it!” was followed by a stream of data. It was his last transmission; the ridge he camped on was within the direct blast zone.


Lives Lost


Damage Costs


Height Before Eruption


Height After Eruption


Homes Destroyed


Mudflows Speed


Estimated Ash

2200sq miles

Ash Covered


Roads Destroyed


Railways Damaged

Mt. St. Helens 41st Anniversary Events

On Shaky Ground

Mt. St. Helens Eruption Timeline

Mount St. Helens is most notorious for its major eruption on May 18, 1980, the deadliest and most economically destructive volcanic event in U.S. history.

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