shadron
Philosopher
- Joined
- Sep 2, 2005
- Messages
- 5,918
About ten years ago, the BBC, at loose ends, decided to locate and scare everyone with a whole new disaster-in-waiting, another Yellowstone caldera eruption (it's been so overdone) to raise awareness of the program's sponsors (at any rate the sponsors when it makes it to America), and keep the BBC relevant. I'll say at the outset that I really admire a lot of the BBC/Horizon doco output, but there are some times when even the best slip up. Casting about, they caught the eye of some scientists in London...
The result was Megatsunami!, a one hour doco on the scientific certainty of a monstrous wave in your future, if you happen to live on the eastern US seaboard. It seems a tsunami of monstrous proportions is headed your way, with the same inevitability as that of the next New Madrid earthquake.
The story starts out in a small (well, maybe 12 square mile) bay in southern Alaska called Lituya Bay. Geologists (in the 50s, so the story goes) noted that the coasts of the bay had been denuded of trees and topsoil up to a half kilometer above the bay, and while they had no ready answer, they took it under advisement for the time being. On July 9, 1958, a 7.7 earthquake caused a huge landslide at the top of the bay, and the resulting waves reached 1740 feet vertically up the slopes. There's a dramatic, but irrelevant story about a man and his son fishing on a boat in the bay that day, which the doco plays well up. So, now we know what caused the slope anomaly. Unfortunately, Wikipedia records that three other landslides have been witnessed in the bay: in 1854 (waves 395 feet high), 1899 (200 feet) and 1936 (490 feet), so I begin to feel there is as much weaving as telling of this story.
What if, the story continues, there is the possibility of scaling this local disaster up into something earth shaking? Enter the London scientists, Dr. Simon Day and Dr. Steven Ward of the Benfield Hazard Research Center of the University College of London. They have been investigating the scaling up of Lituya Bay into a world shaking theory of supertsunamis. In the doco, they concentrate on the Canary Island of Las Palmas off the African coast, which is principally the volcano Cumbre Vieja. A typical strato-volcano, its slopes are mainly loosely held ejecta, and are therefore prone to landslides, similar to avalanches between levels of loose material on a slope. One slope is on the western side of the island, with nothing between it and the US eastern seaboard but about 3400 miles of open Atlantic. If that slope were to slip into the Atlantic, why, we could expect a 100 foot wave on Miami Beach, for starters.
Proof: Well, they have some really neat computer graphics. One shows the difference between an ordinary tsunami (maybe 20, 30 ft tall at most, caused by a basement rock drop/rise) and a supertsunami (caused by a landslide), and it's, by george, 100 ft tall. Then there's a neat experiment at a Swiss (I think, can't be sure) facility where they slide a load of rocks into one end of a 5 foot wide tank maybe 50 ft long, and watch the water dramatically run up the slope at the other end. Finally, some friendly geologists wander about the island and note slippages on the slope, and gasp at dikes which must be holding the water high enough to lubricate the rocks (cue another experiment with a couple of bricks on a slope and a hose feeding water between them, and watch the top one slide off.) Some more graphics, including the typical tsunami graphic, with the red flame shape shooting out of the island towards - yes, the US coast, and some final words about 'not if, but when'.
I'm going to continue this thread with the research I've done and observations I've noted a little later. This little contretemps leads me to some odd conclusions about science, but I'd like to hear other opinions, must certainly from volcano, Correa Neto and/or Dinwar, and other scientists who may have stopped and looked at this, as well as opinions of anyone else interested. More to come.
Link to Megatsunami!:
This is just a trailer. The whole thing doesn't seem to be on YouTube any longer, though it used to be. No doubt it can be found somewhere on the net.
The result was Megatsunami!, a one hour doco on the scientific certainty of a monstrous wave in your future, if you happen to live on the eastern US seaboard. It seems a tsunami of monstrous proportions is headed your way, with the same inevitability as that of the next New Madrid earthquake.
The story starts out in a small (well, maybe 12 square mile) bay in southern Alaska called Lituya Bay. Geologists (in the 50s, so the story goes) noted that the coasts of the bay had been denuded of trees and topsoil up to a half kilometer above the bay, and while they had no ready answer, they took it under advisement for the time being. On July 9, 1958, a 7.7 earthquake caused a huge landslide at the top of the bay, and the resulting waves reached 1740 feet vertically up the slopes. There's a dramatic, but irrelevant story about a man and his son fishing on a boat in the bay that day, which the doco plays well up. So, now we know what caused the slope anomaly. Unfortunately, Wikipedia records that three other landslides have been witnessed in the bay: in 1854 (waves 395 feet high), 1899 (200 feet) and 1936 (490 feet), so I begin to feel there is as much weaving as telling of this story.
What if, the story continues, there is the possibility of scaling this local disaster up into something earth shaking? Enter the London scientists, Dr. Simon Day and Dr. Steven Ward of the Benfield Hazard Research Center of the University College of London. They have been investigating the scaling up of Lituya Bay into a world shaking theory of supertsunamis. In the doco, they concentrate on the Canary Island of Las Palmas off the African coast, which is principally the volcano Cumbre Vieja. A typical strato-volcano, its slopes are mainly loosely held ejecta, and are therefore prone to landslides, similar to avalanches between levels of loose material on a slope. One slope is on the western side of the island, with nothing between it and the US eastern seaboard but about 3400 miles of open Atlantic. If that slope were to slip into the Atlantic, why, we could expect a 100 foot wave on Miami Beach, for starters.
Proof: Well, they have some really neat computer graphics. One shows the difference between an ordinary tsunami (maybe 20, 30 ft tall at most, caused by a basement rock drop/rise) and a supertsunami (caused by a landslide), and it's, by george, 100 ft tall. Then there's a neat experiment at a Swiss (I think, can't be sure) facility where they slide a load of rocks into one end of a 5 foot wide tank maybe 50 ft long, and watch the water dramatically run up the slope at the other end. Finally, some friendly geologists wander about the island and note slippages on the slope, and gasp at dikes which must be holding the water high enough to lubricate the rocks (cue another experiment with a couple of bricks on a slope and a hose feeding water between them, and watch the top one slide off.) Some more graphics, including the typical tsunami graphic, with the red flame shape shooting out of the island towards - yes, the US coast, and some final words about 'not if, but when'.
I'm going to continue this thread with the research I've done and observations I've noted a little later. This little contretemps leads me to some odd conclusions about science, but I'd like to hear other opinions, must certainly from volcano, Correa Neto and/or Dinwar, and other scientists who may have stopped and looked at this, as well as opinions of anyone else interested. More to come.
Link to Megatsunami!:
This is just a trailer. The whole thing doesn't seem to be on YouTube any longer, though it used to be. No doubt it can be found somewhere on the net.
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