How much ash was there from the May 18, 1980 eruption of Mount St. Helens?

During the 9 hours of vigorous eruptive activity on May 18, 1980, about 540 million tons of ash from Mount St. Helens fell over an area of more than 22,000 square miles. The total volume of the ash before its compaction by rainfall was about 0.3 cubic mile, equivalent to an area the size of a football field piled about 150 miles high with fluffy ash.

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Do volcanoes affect weather?

Yes, volcanoes can affect weather and the Earth's climate . Following the 1991 eruption of Mount Pinatubo in the Philippines, cooler than normal temperatures were recorded worldwide and brilliant sunsets and sunrises were attributed to this eruption that sent fine ash and gases high into the stratosphere, forming a large volcanic cloud that...
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Image shows billowing clouds of steam and smoke emanating from the ground
November 30, 2000

Mount St Helens Phreatic Eruption

Phreatic eruption at the summit of Mount St. Helens, Washington. Credit: D.A. Swanson, USGS

Image shows a map with potential volcano hazards to the surrounding area for Mount St. Helens
November 30, 2000

Mount St. Helens Simplified Volcano Hazards Map

Mount St. Helens, Washington simplified hazards map showing potential impact area for ground-based hazards during a volcanic event. More simplified volcano hazard maps for the other Cascades Volcanoes can be found here.

Mount St. Helens soon after the May 18, 1980 eruption
September 10, 1980

Mount St. Helens soon after the May 18, 1980 eruption

Mount St. Helens soon after the May 18, 1980 eruption, as viewed from Johnston's Ridge.

Volcano erupting and spewing a huge cloud of rock and ash into the sky.
May 18, 1980

Mount Saint Helens eruption

On Sunday, May 18, 1980 at 8:32 a.m., the bulging north flank of Mount St. Helens slid away in a massive landslide -- the largest in recorded history. Seconds later, the uncorked volcano exploded and blasted rocks northward across forest ridges and valleys, destroying everything in its path within minutes.

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

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Aerial photo of Mount St. Helens volcano, pre-1980 eruption
September 28, 1979

Aerial photo of Mount St. Helens volcano, pre-1980 eruption

Before the eruption of May 18, 1980, Mount St. Helens' elevation was 2,950 m (9,677 ft). View from the west, Mount Adams in distance. S. Fork Toutle River is valley in center of photo.

Mount Adams elevation is 3,745 m (12, 286 ft). Mount St. Helens was the smallest of five major volcanic peaks in Washington State.

Mount St. Helens

Mount St. Helens

Prior to 1980, Mount St. Helens had the shape of a conical, youthful volcano sometimes referred to as the Mount Fuji of America. During the 1980 eruption the upper 400 m (1,300 ft) of the summit was removed by a huge 

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