On May 18, 1980, 57 people died when an earthquake struck below the north face of Mount St. Helens in Washington state. The earthquake triggered a catastrophic landslide and a major volcanic eruption of the mountain, scattering ash across a dozen states in the Pacific Northwest. The Mount St. Helens eruption was the most significant volcanic eruption in the contiguous 48 U.S. states since a smaller volcanic eruption of Lassen Peak in California in 1915.

A lot of time has passed since 1980, but many people have never forgotten that fateful day. They will always remember the sudden lateral blast and the massive mudflows. But for the individuals who don’t remember that day, what exactly happened during the eruption? Could Mount St. Helens ever erupt again?

An active volcano

People knew Mount St. Helens was active long before its 1980 eruption. In the early 1700s, Pacific Northwest Indians regarded the volcanoes as “warrior gods who would sometimes throw red-hot boulders at each other.” In 1800, the Sanpoil and Spokane people told the first missionaries and traders visiting the region about past eruptions.

They claimed that “the ashes fell several inches deep all along the Columbia and far on both sides. Everyone was so badly scared that the whole summer was spent in praying.” Then, in 1842, missionary Josiah Parrish experienced a rain of ash, most likely coming from Mount St. Helens. Minor eruptions, with small explosions and lava flows, occurred in 1898, 1903, and 1921.

However, the volcano had remained relatively quiet throughout the 20th century. People were sure the volcano was perhaps finished with its eruptions. But you should know better than to ever question nature.

Earthquakes and an eruption, oh my…

On March 1, 1980, researchers at the University of Washington installed a new system of seismographs to monitor the potential earthquake activity in the Cascade Mountains, especially around Mount St. Helens. Shortly after, on March 20, a 4.2-magnitude earthquake rumbled below the volcano. Three days later, on March 23, a 4.0-magnitude earthquake shook the grounds, intensifying over the next few days. By March 25, the new seismographs were detecting an average of three 4.0-magnitude earthquakes every hour. Yikes!

Smaller eruptions continued in the month of April until the morning of May 18, when United States Geological Survey volcanologist David Johnston woke up at his campsite six miles north of Mount St. Helens. That morning, a 5.1-magnitude earthquake rocked the volcano. Johnston radioed in: “This is it!”

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The earthquake triggered the largest landslide in recorded U.S. history. Mount St. Helens erupted and scattered ash across a dozen states. The earthquake removed 1,300 feet off the top of the volcano, sending pyroclastic flows across the landscape. Forests were immediately flattened. The eruption melted snow and ice, as well as generated massive mudflows. For many people, it was too late to seek shelter. A total of 57 people lost their lives in the disaster.

Could it erupt again?

The 1980 eruption of Mount St. Helens caused many people to fear volcanoes. We don’t blame them. Who would want to experience lava flows, mudslides, and ash? With this in mind, it’s not surprising people wonder if the volcano could ever erupt again. If so, when would that be?

Today, scientists keep a watchful eye on the volcano, as well as other volcanoes in the Pacific Northwest region. Mount St. Helens is located on the Cascadian Subduction Zone, which means another eruption is inevitable. But predicting that eruption is far too difficult. Instead, long-term seismic data observes when a volcano is on the verge of erupting, said Benjamin Edwards, volcanologist and professor of Earth Science at Dickinson College.

If the seismic measurements depict a jump in the number of earthquakes near Mount St. Helens, this raises some concern. However, there’s no reason to panic right now. For the last few years, the seismic activity around the volcano has fallen at a normal rate. Mount St. Helens most likely won’t erupt anytime soon. But if it does, hopefully we’re more prepared than the heartbreaking situation in 1980.