On May 18, 1980, one of the most violent and cataclysmic natural disasters of the modern era took place.
Mount St. Helens, a stratovolcano located approximately 100 miles or 160 kilometers south of Seattle, exploded.
The effects of the explosion could be noticed over 1,000 miles away, and it forever changed the landscape of southern Washington State.
Learn more about Mount Saint Helens, the explosion, and its future, on this episode of Everything Everywhere Daily.
Mount St. Helens is a stratovolcano located in the Cascade Mountains in southern Washington State.
Prior to the eruption, it was the 5th highest peak in Washinton State, with a height of 9,678 feet or 2,950 meters.
Mount St. Helens is part of the Ring of Fire, which is a collection of volcanoes that ring the Pacific Ocean. Mount St. Helens is one of several volcanoes in the Cascade Mountains that all share a similar origin, including Mount Adams, Mount Rainer, and Mount Hood.
These volcanoes are created by the Juan de Fuca tectonic plate in the Pacific Ocean, subducting underneath the North American tectonic plate.
Prior to its eruption, it looked like a classic stratovolcano. It was highly symmetric and had a top that was often covered in snow and ice. Because of how it looked, it was called the “Mount Fuji of America.”
The mountain had several different names given to it by the native people of the region. The Yakima people called the mountain “Louwala-Clough” which means “the smoking mountain.”
The Chehalis people called it “nšh´ák´,” which means “water coming out,” and the Upper Chinook called it “aka akn,” which means “snow mountain.”
The name Mount St. Helens was given to the peak by the British Navy officer George Vancouver. On May 19, 1792, while surveying the coast of the Pacific Northwest on the HMS Discovery, he spied the mountain. He named it after Alleyne Fitzherbert, 1st Baron St Helens.
Alleyne Fitzherbert was a British ambassador to Russia, Chief Secretary for Ireland, and later ambassador to Spain. The title “Baron St. Helens” was created for him in 1791 as a title under the system of Irish Peerage.
St. Helens is a village in County Wexford. In 1801, he was named Baron St. Helens in the British peerage system, named after St. Helens on the island of Wight.
The title Baron of St. Helens disappeared after his death but was re-established in 1964 as a hereditary barony, this time named after St Helens, Merseyside, a town not far from Liverpool.
As far as geologists can tell, there was some sort of eruption on the mountain around the year 1800.
The Lewis and Clark expedition spotted the mountain in 1806 but reported no volcanic activity.
The first documented volcanic activity occurred in 1835. An eruption in 1842 was dubbed “the great eruption,” although it paled in comparison to what happened in 1980.
There was subsequent activity in 1845, 1854, and 1857.
After that, Mount St. Helens became relatively quiet.
The story of Mount St. Helens can probably best be described by Vladimir Lenin’s account of the Russian Revolution; “there are decades when nothing happens, and there are weeks when decades happen.”
Mount St. Helens became alive again on March 15, 1980, only two months before its eruption. Several earthquakes were recorded on the volcano, indicating to vulcanologists that magma below the mountain was moving.
There were thousands of these small earthquakes, in addition to steam vents that appeared on the side of the mountain. At this point, it was difficult to determine exactly what was going to happen. However, it was only a matter of days before geologists realized something big was happening.
On March 20, a bulge in the mountain started to appear. On March 27, steam venting caused a new crater to form at the top along with a 7000-foot-high column of ash.
On April 1, geologists detected harmonic tremors, which are usually associated with the movement of underground magma. This was alarming and caused in the governor of Washington to declare a state of emergency in the area.
Throughout April, the mountain showed visible changes every day, the biggest of which was the size of the bulge on the north face of the mountain.
The bulge was growing 5 to 6 feet or 1.5 to 1.8 meters per day. It grew to a maximum size of 400 feet or 120 meters by mid-May.
Geologists became concerned that the bulge, known as a cryptodome, could collapse, causing a massive avalanche, and such an avalanche could then cause a massive eruption.
The area was evacuated, but there were a few people who stubbornly remained. The most famous of which was the 83-year-old owner of the nearby Spirit Lake Lodge, Harry R. Truman….not to be confused with the former president of the United States, Harry S Truman.
Spirit Lake was located right on the slope of the mountain.
Truman became a minor celebrity in the weeks leading up to the eruption. He famously said, “If the mountain goes, I’m going with it. This area is heavily timbered, Spirit Lake is in between me and the mountain, and the mountain is a mile away, the mountain ain’t gonna hurt me.”
Truman honestly didn’t think that the mountain was going to erupt, and if it did, he didn’t really have any sense of just how big of an eruption it would be.
On May 16, much of the visible activity on the mountain actually ceased. This actually resulted in reduced media attention, but it was nothing more than a calm before the storm.
The geologist’s worst-case scenario occurred at 8:32 am on the morning of Sunday, May 18.
An earthquake with a magnitude of 5.1 on the Richter scale took place. The earthquake resulted in the large, unstable bulge on the north face of the mountain to collapse in a massive avalanche. The avalanche was the largest avalanche in recorded human history.
The sudden collapse of the north face of the mountain resulted in the sudden release of all the pent-up, high-pressure steam and gas. Everything burst out of the mountain laterally. The top 1,300 feet or 400 meters of the mountain disappeared in the explosion.
This resulted in a massive pyroclastic flow off the north side of the mountain. If you remember back to my episode on the eruption of Mount Vesuvius in Italy, a pyroclastic flow is a rapidly moving cloud of superheated gas and volcanic ash.
It is so hot that it will instantly kill anything it touches and so fast that there is no way to avoid it.
Everything in a 230 square mile or 600 square kilometer area was destroyed by the pyroclastic flow, which moved at speeds over 300 miles per hour or 480 kilometers per hour. When it was first ejected, the speeds might have been greater than Mach 1.
The sound of the explosion was so great that it was reported to have been heard as far away as British Columbia, Montana, and Northern California. However, there was an odd phenomenon where the explosion wasn’t heard. No one in Portland, Oregon, for example, heard the explosion. This was known as the quiet zone.
The quiet zone is believed to have been created by temperature differences in the atmosphere and local topography.
While the pyroclastic flows devastated the area immediately surrounding the volcano, what most people remember from that day is the giant ash column that rose into the sky.
Winds carried the ash column in an east-northeasterly direction. The eruption took place at 8:32 am. By 9:45, the ash cloud had reached Yakima, Washington, 90 miles or 140 kilometers away. There it dropped five inches of ash on the community.
The ash fell on Yellowstone National Park, and there were reports of at least some ash falling as far away as Minnesota and Oklahoma.
The ash disrupted air travel over much of the country and closed roads in Washington State. Many vehicles had fine particles of ash which clogged their air intake systems. It also caused blackouts in some places when ash caused transformers to short-circuit.
Ash removal wasn’t like snow removal. Ash doesn’t melt. It took at much as 10 weeks for parts of Washington to clear the ash from all the roads. Designated ash disposal sites had to be set up, which often consisted of old queries or landfills. Many locales just piled up it and then covered it with topsoil so it wouldn’t blow away again.
In the end, an estimated 57 people were killed in the eruption, including Harry Truman. Truman was believed to have been killed instantly from heat shock when the pyroclastic flows hit Spirit Lake. His remains and his lodge are buried under 150 feet or 46 meters of debris.
Many of the dead were geologists and photographers who were observing the mountain when the explosion took place. There is doubt as to the death toll as several people when missing, and it can’t be proven that they died in the eruption.
The total cost of the damage from the eruption was over one billion dollars in 1980.
The May 18 eruption wasn’t the end of activity on the mountain. On May 25, there was another ash column that sent ash into Oregan, and there were further ash plumes on June 12, July 22, and August 7.
Activity on the mountain has continued for years, but it has mostly been in the form of building a lava dome on the mountain. Activity continued until January 2008.
In 1982, the Mount St. Helens National Volcanic Monument was established, and today, you can visit the mountain and learn the full story of the eruption at the visitor center.
It has taken decades, but wildlife around the mountain has started to come back.
You can actually climb Mount St. Helens today. Unlike other mountains in the Cascades, it is more of a hike than a technical climb.
In the big picture of world history and geology, the eruption of Mount St. Helens was not even close to being one of the largest volcanic eruptions. What made it noteworthy was that it happened in a part of the world that was relatively well-populated, and it occurred during an era when the event could be recorded with photos and video.
As such, it captured the attention of the public, and it was something that many people still remember.
On the Volcanic explosivity index, which ranks volcanic explosions on a scale of zero to eight, the explosion of Mount St. Helens only ranks a 5, on a par with the eruption of Vesuvius in 79 and the 2022 eruption of the Hunga Tonga–Hunga Ha?apai volcano in Tonga.
The Mount Pinatubo eruption in the Philippines in 1991 was almost an order of magnitude larger, and the Mount Tambora eruption of 1815 was two orders of magnitude larger.
Could Mount St. Helens erupt again?
The answer is yes, and in fact, at some point, it almost certainly will. Given how the current lava dome on the mountain has developed, the current thinking among geologists is that the next eruption will be even more powerful. Basically, the cork on the bottle has been put on even tighter, which will require even more pressure to open it.
Small earthquakes have been reported on the mountain in just the last few years.
Another Mount St. Helens eruption isn’t even the most worrying thing that could happen in the Cascades. That distinction belongs to Mount Rainier, the volcano which overlooks the city of Seattle.
The 1980 eruption of Mount St. Helens wasn’t the first such eruption, it wasn’t the largest, and it won’t be the last. However, for those who experienced it and remember it, it was a landmark moment and something that they will never forget.
The Executive Producer of Everything Everywhere Daily is Charles Daniel.
The associate producers are Thor Thomsen and Peter Bennett.
I have a whole bunch of Spotify comments for you today. These tend to be shorter and left for individual episodes.
From my episode on the most dangerous substances,
I love listening to these podcasts! I learn so much, and it’s fun!
Great, as always. I am so hooked on your snack-sized knowledge bites. Greetings from the most beautiful Eastern Freestate clothed currently in its autumn splendor.
Now I have to expand my list of favorite episodes. I don’t even know a thing about chemistry, and I loved this. Gary, you are amazing!
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From the Moneyball episode,
Another great episode! This podcast is my first listen every day. Closing in on Double Completionist Club. Do we get a gold jacket, a keycard to the VIP Lounge, or do we just mingle with the Singles?
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FYI Aaron, when you listen to every episode twice, you get Elite Platinum status in the Completionist Club.
From the Namibia episode,
Milton R Patch III
I visited Namibia a month ago, it was my first time outside of North America, and yes, it was Amazing. Car rentals were very easy, and Windhoek beer is good. I love your podcast, but Go, Chicago Bears!
Thanks, Milton. You are right about Namibia, but oh so wrong about the Bears.
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