On May 18, 1980, the course of Washington’s history was changed forever when Mount St. Helens erupted. The incident was not without warning, but no one was fully prepared for what ended up being the most disastrous volcanic eruption in United States history. And while time has brought some changes and regrowth, the mountain will never look the same.
![](https://img-aws.ehowcdn.com/700x/cdn.onlyinyourstate.com/wp-content/uploads/2017/12/Mount-St.-Helens-National-Volcanic-Monument-15237018282-700x525.jpg)
From far away, you’d never guess what once occurred here.
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It was all caused by an injection of magma at the shallow depth below the volcano that created a large bulge and fracture system on the mountain’s north slope.
![](https://img-aws.ehowcdn.com/700x/cdn.onlyinyourstate.com/wp-content/uploads/2017/12/Mount-St.-Helens-and-her-shadow-36322375385-700x467.jpg)
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This caused the volcano to explode, erupting 80,000 feet into the air. The thermal energy released during the eruption was equal to 26 megatons.
![](https://img-aws.ehowcdn.com/700x/cdn.onlyinyourstate.com/wp-content/uploads/2017/12/Mount-St.-Helens-36153757912-700x467.jpg)
Thousands of animals were also killed, and hundreds of square miles were reduced to wasteland. The damages reached $1 billion, equivalent to $3 billion today.
![](https://img-aws.ehowcdn.com/700x/cdn.onlyinyourstate.com/wp-content/uploads/2017/12/Mount-St.-Helens-36278651836-700x467.jpg)
That being said, this is still an active volcano, and another eruption could occur — although experts believe the next one will be mild.
Do you remember the day Mount St. Helens erupted? If not, you probably learned all about it in school. These Washington facts, however, remain largely unknown.
source onlyinyourstate.com