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FAQs

Mount St. Helens is the most active volcano in the contiguous United States, which makes it a fascinating place to study and learn about. Scientists receive many questions about the volcano. Here are some of the most frequently asked questions.

How old is Mount St. Helens?

The eruptive history of Mount St. Helens began about 40,000 years ago with dacitic volcanism, which continued intermittently until about 2,500 years ago. This activity included numerous explosive eruptions over periods of hundreds to thousands of years, which were separated by apparent dormant intervals ranging in length from a few hundred to about 15,000 years.The range of rock types erupted by...

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How old is Mount St. Helens?

The eruptive history of Mount St. Helens began about 40,000 years ago with dacitic volcanism, which continued intermittently until about 2,500 years ago. This activity included numerous explosive eruptions over periods of hundreds to thousands of years, which were separated by apparent dormant intervals ranging in length from a few hundred to about 15,000 years.The range of rock types erupted by...

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What is the origin of the name "Mount St. Helens"?

Some Indians of the Pacific Northwest variously called Mount St. Helens 'Louwala-Clough,' or 'smoking mountain.'The modern name, Mount St. Helens, was given to the volcanic peak in 1792 by seafarer and explorer Captain George Vancouver of the British Royal Navy. He named it in honor of fellow countryman Alleyne Fitzherbert, who held the title ‘Baron St. Helens’. Fitzherbert at the time served as...

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What is the origin of the name "Mount St. Helens"?

Some Indians of the Pacific Northwest variously called Mount St. Helens 'Louwala-Clough,' or 'smoking mountain.'The modern name, Mount St. Helens, was given to the volcanic peak in 1792 by seafarer and explorer Captain George Vancouver of the British Royal Navy. He named it in honor of fellow countryman Alleyne Fitzherbert, who held the title ‘Baron St. Helens’. Fitzherbert at the time served as...

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How far did the ash from Mount St. Helens travel?

The May 18, 1980 eruptive column at Mount St. Helens fluctuated in height through the day, but the eruption subsided by late afternoon. By early May 19, the eruption had stopped. By that time, the ash cloud had spread to the central United States.Two days later, even though the ash cloud had become more diffuse, fine ash was detected by systems used to monitor air pollution in several cities of...

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How far did the ash from Mount St. Helens travel?

The May 18, 1980 eruptive column at Mount St. Helens fluctuated in height through the day, but the eruption subsided by late afternoon. By early May 19, the eruption had stopped. By that time, the ash cloud had spread to the central United States.Two days later, even though the ash cloud had become more diffuse, fine ash was detected by systems used to monitor air pollution in several cities of...

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How high was Mount St. Helens before the May 18, 1980 eruption? How high was it after?

Before May 18, 1980, Mount St. Helens' summit altitude of 9,677 feet (2,950 meters) made it only the fifth highest peak in Washington State. It stood out handsomely, however, from surrounding hills because it rose thousands of feet above them and had a perennial cover of ice and snow. The peak rose more than 5,000 feet (1,524 meters) above its base, where the lower flanks merge with adjacent...

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How high was Mount St. Helens before the May 18, 1980 eruption? How high was it after?

Before May 18, 1980, Mount St. Helens' summit altitude of 9,677 feet (2,950 meters) made it only the fifth highest peak in Washington State. It stood out handsomely, however, from surrounding hills because it rose thousands of feet above them and had a perennial cover of ice and snow. The peak rose more than 5,000 feet (1,524 meters) above its base, where the lower flanks merge with adjacent...

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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 (57,000 square kilometers). The total volume of the ash before its compaction by rainfall was about 0.3 cubic mile (1.3 cubic kilometers), equivalent to an area the size of a football field piled about 150 miles (240 kilometers)...

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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 (57,000 square kilometers). The total volume of the ash before its compaction by rainfall was about 0.3 cubic mile (1.3 cubic kilometers), equivalent to an area the size of a football field piled about 150 miles (240 kilometers)...

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How would an eruption of Mount Rainier compare to the 1980 eruption of Mount St. Helens?

Eruptions of Mount Rainier usually produce much less volcanic ash than do eruptions at Mount St. Helens. However, owing to the volcano's great height and widespread cover of snow and glacier ice, eruption-triggered debris flows (lahars) at Mount Rainier are likely to be much larger--and will travel a greater distance--than those at Mount St. Helens in 1980. Furthermore, areas at risk from debris...

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How would an eruption of Mount Rainier compare to the 1980 eruption of Mount St. Helens?

Eruptions of Mount Rainier usually produce much less volcanic ash than do eruptions at Mount St. Helens. However, owing to the volcano's great height and widespread cover of snow and glacier ice, eruption-triggered debris flows (lahars) at Mount Rainier are likely to be much larger--and will travel a greater distance--than those at Mount St. Helens in 1980. Furthermore, areas at risk from debris...

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