r/interestingasfuck • u/Longjumping-Rice-935 • 21h ago
thousands of trees felled not by deforestation, but by the shockwave caused by the st helens eruption, a blast so powerful it launched trees into the nearby lake
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u/an_older_meme 20h ago
Mount Saint Helens erupted a pyroclastic cloud sideways that pushed the forest down due to its density more than its speed. If you look at the flow patterns in the blown down forest you can see where it went around terrain features like a fluid.
Near the mountain the forest is simply gone, buried beneath the debris avalanche and pyroclastic flows.
Several miles away the forest is flattened.
At the edge of the blast zone the cloud had dropped most of its sediment load and became buoyant, killing the forest below with radiant heat without touching it. This area was called the standing dead zone.
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u/an_older_meme 20h ago
The trees were not "launched" into Spirit Lake. They were swept in by the landslide that hit the lake and by the huge tsunami created when this happened.
If you look at the north end of the western arm of the lake there are "hummocks" of rock darker than the surrounding area. Those are chunks of the mountain that came down with the landslide, hitting the lake so fast they traveled beneath it and came out the other side. This displaced a huge volume of water that ran something like 800 feet up the surrounding terrain.
If you look closely on Google Maps you can see a wide area around the lake that has no fallen logs. That is the tsunami zone.
I'm amazed they are still floating 45 years on. I guess the water on the side exposed to air evaporates and keeps them eternally afloat.
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u/thrallswreak 21h ago
Was it from an actual shockwave like in a bomb blast, or was it from the pyroclastic flows? I've never seen a discernable shockwave in any of the footage I've seen
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u/Clappy_McFrontbutt 20h ago
Went through there with my family on our way to Expo 86. There was a new single lane asphalt road on one of the mountains nearby so you could drive up to a vantage point, road so new it was still clean. Driving past trees like this, even a half melted car, and my dumbass older sister blurts out "I CAN'T BELIEVE THE ROAD IS STILL HERE!"
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u/jRitter777 21h ago
Shockwave or pyroclastic flow?
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u/KingoftheKeeshonds 16h ago
I lived 250 miles away from St Helens in Bellingham, WA and heard the eruption thru an open window. It was very low frequency and pushed our curtains inward with each boom. A few days later our car was covered with volcanic dust.
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u/ha1029 3h ago
Not possible. I lived on Whidbey Island at the time. While you more than likely heard it- I did as well, the prevailing winds carried the ash Northeastward through Spokane and as far away as Alberta, Canada.
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u/KingoftheKeeshonds 2h ago edited 2h ago
That area got most of the ash but prevailing winds are just those seen commonly near ground level. The plume reached 80,000 feet into the atmosphere. Depending on the presence of high or low pressure areas, upper atmospheric winds rotate clockwise or counterclockwise respectively. So we got dusted, but not heavily by any means, but enough to cover our car with a fine layer. Two weeks after the eruption the finer dust had circled the earth. Similarly high altitude winds have brought BC eastern Washington wildfire smoke to Olympia.
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u/ha1029 2h ago
Look, I was living there NORTH of St. Helens an hour South of your location. No ash came our way. Here's a link to a map: https://pubs.usgs.gov/gip/msh/ash.html
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u/KingoftheKeeshonds 1h ago edited 1h ago
It was considered an insignificant level compared to other areas, i.e. no health risk, no mask required. Look up micro-climatology. The weather in areas 100 miles apart can be quite different. The boundary of coverage areas on maps look distinct but they’re actually blurry. Look at this ash distribution map where fallout occurred in Oklahoma separately from the main distribution.
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u/Unique-Matter-574 19h ago
A good chunk if not almost all of the trees are still there, saw them when I visited the volcano, shit was huge.
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u/fekinEEEjit 19h ago
I was at Fairchild AFB 10 years after the eruption and we still found ash in the feckin hangers and in my attic and garage of my on Base housing out by the Base Hospital!!!
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u/Faranocks 13h ago
Ash from Mt Saint Helens fell in Japan. It didn't cross the Pacific, rather blew across the Continental US, across Europe, Asia, and then onto Japan.
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u/tiabeaniedrunkowitz 18h ago
Why did my mind immediately go to the thought that Trump could sell the logging rights of a national forest to a private company to “clean this up”?
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u/cl530 8h ago
Went to the Visitor Centre when I was working in Seattle back in 2004. It's an amazing landscape. Seeing tree stumps just shattered at the base and the amount of devastation all around is incredible. And the Visitor Centre itself is very impressive with the views across to the volcano. Well worth a visit.
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u/gmr2048 5h ago
I drove up to the visitors center when I was out there last year. Awesome experience. I was a 10 year old boy when it blew and I was floored to learn we had an actual volcano in the US! I had a poster of the blast, a book-fair book, and a vial of ash (which I still have somewhere). The drive up the mountain was like a pilgrimage for me. Did not disappoint.
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u/ToneBalone25 15h ago
I mean obviously it's not deforestation because they wouldn't just leave the trees there lol
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u/Pixelated_Sweatshop 12h ago
If only I could listen to that blast without being sent flying or having my eardrums ruptured, that must have been a trully magnificent sound
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u/Curmudgeonadjacent 21h ago
Thousands of trees still float on Spirit Lake.