On this day, May 18, 1980, Mount St. Helens in Washington erupted for nine hours, killing 57 people and triggering the largest landslide in human history.

Mount St. Helens was at 9,677 feet before the eruption, according to the US Geological Survey (USGS) website. It was the fifth highest mountain in the state of Washington.

“However, it stood out beautifully from the surrounding hills, because it towered thousands of feet above them and had a perennial cover of ice and snow,” the site says.

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That changed on May 18, when the volcano erupted for the first time in more than a century, according to the USGS.

When the dust literally and figuratively settled after the eruption, Mount St. Helens was found to have lost approximately 1,300 feet from its cone.

Instead, a horseshoe-shaped crater formed in its place, according to the USGS.

The highest point of the crater, located on the southwest side of the mountain, is 8,365 feet, according to the website.

According to the US Geological Survey, the eruption occurred almost exactly two months after seismic activity began on the long dormant volcano.

On March 16, 1980, a “series of small earthquakes” began to shake the area. Eleven days later, on March 27, after hundreds of small earthquakes, Mount St. Helens experienced a relatively small eruption, the first since 1857.

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During this eruption, “explosions of steam created a 60 to 75 m (200 to 250 ft) wide crater in the volcano’s ice cap and covered the snow-covered southeast sector in dark ash,” the USGS said.

These eruptions continued until April 22, according to the US Geological Survey.

After a roughly two-week halt in volcanic activity, smaller eruptions and earthquakes continued from May 7 to 17.

The famous aerial view of the eruption of Mount St. Helens on May 18, 1980. Ash poured into the atmosphere for nine hours. (Getty images)

“By that time, more than 10,000 earthquakes had rocked the volcano, and the northern slope had risen by about 140 m (450 ft), forming a noticeable bulge,” the USGS said.

This bulge was “strong evidence that the molten rock (magma) had risen high into the volcano” and was growing at a rate of up to five feet a day.

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At 8:32 a.m. on May 18, a magnitude 5.1 earthquake “without immediate warning” struck Mount St. Helens, setting off a “rapid series of events,” the USGS said.

“At the same time as the earthquake hit, the northern bulge and the top of the volcano slid off in a huge landslide — the largest avalanche of debris on Earth in the history of mankind,” they said.

“A small, dark, ash-rich plume of eruption rose directly from the base of the debris avalanche ledge, and another from a summit crater rose about 200 m (650 ft) high,” they said.

Mount St. Helens has lost about 1,300 feet of elevation since the eruption. (Getty images)

The USGS added that the volume of the avalanche is equivalent to one million Olympic pools.

After the landslide, the destruction continued.

The landslide removed part of the “cryptodome,” which was a “very hot and highly pressurized body of magma,” the USGS said.

After the removal of the kiptomol, Mount St. Helens’ magma system depressurized, causing “powerful eruptions that swept through the sliding debris,” knocking the mountain down 1,000 feet.

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The cloud of tephra, or rock fragments, reached 15 miles in 15 minutes, the USGS notes.

The effects of the initial eruption were devastating.

“Virtually no trees remain of what was once dense forest” within a six-mile radius of the former summit, and other trees were knocked to the ground and burned, the USGS said.

The former dense forest surrounding Mount St. Helens was destroyed by a landslide and volcanic eruption in May 1980. (Getty images)

“The destroyed area of ​​600 km2 (230 miles) was covered with a deposit of hot debris brought by the explosion,” the report said.

The eruption then became a “Plinian eruption,” defined as “an eruption that produces a sustained convection plume of pyroclasts and gas rising more than 25 km above sea level,” the Science Direct website says.

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The Plinian eruption lasted nine hours, throwing 520 million tons of ash into the air.

The ash was so thick that the city of Spokane, Washington, located 250 miles from Mount St. Helens, plunged into total darkness, the USGS said.

At the time, Getty reported that over four inches of ash covered Yakima, Washington.

Rick Cole, director of emergency services at Yakima, shakes volcanic ash from his car. (Getty images)

“Large ash falls have occurred as far away as central Montana, with ash falling noticeably east as far as the Great Plains in the central United States, over 1,500 km (930 miles) away,” the USGS said in a statement.

“The ash cloud spread across the US in three days and orbited the Earth in 15 days.”

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The explosion also caused something called a “lahar,” which is “an Indonesian term for a hot or cold mixture of water and rock debris that flows down the slopes of a volcano and usually ends up in a river valley,” the USGS said in a statement.

In the case of Mount St. Helens, the snow peak melted during the initial eruption.

This rush of water, combined with the rock flow, created the lahar.

A pickup truck covered in ash and other debris from the eruption of Mount St. Helens. (Getty images)

According to an article in American Scientist, in the weeks leading up to May 18, people living near Mount St. Helens were evacuated.

The area immediately surrounding Mount St. Helens was divided into a “red zone” and a “blue zone”.

Of the 57 people who died in the eruption, only one – Harry Randall Truman – did not have special permission to be near the mountain on the day of the eruption, and most of the deaths actually occurred outside the blue zone, American Scientist notes. .

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Truman, an 83-year-old man who lived near Mount St. Helens for 54 years, refused to comply with the evacuation order and leave the red zone.

Harry R. Truman, owner of the Spirit Lake Lodge and longtime resident of the Mount St. Helens area, refused to evacuate. He died during the eruption. (Getty images)

In a colorful National Geographic interview before the eruption, Truman said, “I’ll stay here because I’ll tell you why, my home and my (expletive) life is here.”

“My wife and I swore years ago that we would never leave Spirit Lake. We liked it. It is a part of me and I am a part of this (abusive) mountain,” he said.

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Truman’s remains have never been found.