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Ash plume (close up) from May 18, 1980 Mount St. Helens. Plume move...
May 18, 1980

Ash plume (close up) from May 18, 1980 Mount St. Helens. Plume move...

For more than nine hours a vigorous plume of ash erupted, eventually reaching 20-25 km (12-15 mi) above sea level. By early May 19, the devastating eruption was over.

Eruption column from May 18, 1980 Mount St. Helens eruption, viewed...
May 18, 1980

Eruption column from May 18, 1980 Mount St. Helens eruption

On May 18, 1980, at 8:32 a.m. Pacific Daylight Time, a magnitude 5.1 earthquake shook Mount St. Helens. The bulge and surrounding area slid away in a gigantic rockslide and debris avalanche, releasing pressure, and triggering a major pumice and ash eruption of the volcano. Thirteen-hundred feet (400 meters) of the peak collapsed or blew outwards. As a result, 24 square

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May 18, 1980

Mount St. Helens in eruption, May 18, 1980

Mount St. Helens erupted catastrophically on May 18, 1980 beginning at 8:32 a.m. USGS geologist Don Swanson photographed and filmed the eruption from about 9:30 a.m. to 12:30 p.m., documenting the rising ash column and ground-hugging pyroclastic density currents. Swanson filmed the eruption from a fixed-wing surveillance aircraft using a Bell & Howell hand-wound 16mm

video thumbnail: Mount St. Helens 1980 Ash Cloud as Seen From Space
May 17, 1980

Mount St. Helens 1980 Ash Cloud as Seen From Space

Eruptive activity at Mount St. Helens captured the world’s attention on May 18, 1980 when the largest historical landslide on Earth and a powerful explosion reshaped the volcano. A volcanic ash cloud spread across the US in 3 days, and encircled the Earth in 15 days.

This mini-movie compiled from individual satellite images taken in 1980 shows the ash cloud as it

Mount St. Helens on May 17, 1980, one day before the devastating er...
May 17, 1980

Mount St. Helens on May 17, 1980, one day before the devastating er...

Mount St. Helens on May 17, 1980, one day before the devastating eruption. The view is from Johnston's Ridge, six miles (10 kilometers) northwest of the volcano.

Bulge on the north slope of Mount St. Helens before the May 18, 198...
May 3, 1980

Bulge on the north slope of Mount St. Helens before the May 18, 198...

Bulge on the north slope of Mount St. Helens before the May 18, 1980 eruption. Sugar Bowl on left (east) side of bulge and Goat Rocks on right (west) side, viewed from the air.

Bulge on the north side of Mount St. Helens developed as magma push...
April 27, 1980

Bulge on the north side of Mount St. Helens developed as magma push...

A "bulge" developed on the north side of Mount St. Helens as magma pushed up within the peak. Angle and slope-distance measurements to the bulge indicated it was growing at a rate of up to five feet (1.5 meters) per day. By May 17, part of the volcano's north side had been pushed upwards and outwards over 450 feet (135 meters).

View from the northeast of a small phreatic eruption on Mount St. H...
April 10, 1980

View from NE of a small phreatic eruption on Mount St. Helens befor...

On March 20, 1980, after a quiet period of 123 years, earthquake activity once again began under Mount St. Helens volcano. Seven days later, on March 27, small phreatic (steam) explosions began.

Flyover view of Mount St. Helens prior to the catastrophic eruption.
April 10, 1980

Mount St. Helens prior to the catastrophic eruption

Mount St. Helens prior to the catastrophic eruption of May 18, 1980. Streams and lava flows also visible. View is looking southerly from oblique aerial view. Mount Hood in distance.

View looking west of Mount St. Helens' summit after several small e...
March 30, 1980

View looking west of Mount St. Helens' summit after several small e...

View looking west of Mount St. Helens' summit after several small explosive eruptions. The smaller of the two pit craters was formed first on March 27. Subsequent eruptions opened the farther crater.