Naked Science Forum
On the Lighter Side => That CAN'T be true! => Topic started by: chris on 01/02/2003 12:45:15
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The biggest wave ever witnessed measured a staggering 1720 feet high and occurred on 9th July 1958 at Lituya Bay, Alaska.
The wave was in fact a tsunami triggered by a massive local earthquake, measuring about 8 on the Richter Scale, which caused about 40 million cubic yards of rock, debris and soil to tip into the bay. The resulting wave swept away trees to a height of 1720 feet above sea level on the adjacent slopes, indicating the magnitude of the wave. Miraculously a number of boats anchored in the bay, together with the fishermen on-board, lived to tell the tale.
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Being a geologist, i'm particularly interested in such events. Numerous studies were conducted at the Swiss Federal Institute of Technology to try and work out how the 90 million tonnes of rock that fell into the water created a 1km high wave. If i remember correctly, they used a scale model, a fraction of the size. Understanding tsunamis like this may aid us when judgement day comes on the island of Las Palma in the canary islands.
During its last major eruption in 1949, half the island subsided by around 4metres along a 2 km fissure. The reason this occured is simple. Water. The island, although volcanic, is saturated with water. It is trapped in permeable layers of ash but restricted by impermeable verticle dykes. It is believed that when eruptiuons occur, the water expands and begins to make the "balast like" dykes unstable and thus subside.
It is known that a 20km long piece of island will one day descend into the ocean. This could happen tomorrow, or possibly in 1000 years, but it will happen.
Waves from this event will take just 8 hours to cross the Atlantic before they strike the entire east coast of the USA from New York to Miami.
For an idea of the wave's path visit:
www.bghrc.com/CentreNews/press%20releases/LaPalma4.jpg
And just to let you kno, we are not safe in the UK either, also hit will be western Africa, France, then the UK and countries along the English Channel.
SMILE EVERYONE [;)]
Thats Economics...
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Hopefully there will be an adequate warning system in place.
What about the San Andreas fault? Any indication of when it will go and what the path will look like?
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I guess you wouldn't mind if it hit America, so long as Canada was spared !
PT
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To be fair, with wave refraction, canada isn't safe either...
Donnah, as for adequate warning... the volcano is being monitored and i'm sure that once the slide occurs then warning will be sent over the pond. What would be interesting to know is if any of the East Coast of the US knows about this danger and whether any evacuation plans have been drawn up. Theyd probably have 6 to 7 hours to evacuate the whole of the east coast... you'd need people inland by more than 20 miles in some cases, is this possible?? i'd be amazed if people were evacuated this quickly.
The main disadvantage that the US coastline has a gently sloping continental shelf leading onto a flat beach, no real topography lines the coast meaning the full force of the wave is able to push inland.
Thats Economics...
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Good.
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This is great news indeed !
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I doubt very much that the eastern U.S. or Atlantic Canada are aware of the issue. I also doubt that six or seven hours would be adequate evacuation time. What about people who are hospitalized or incarcerated?
I heard that an arm of the San Andreas fault runs right up near Calgary, is that true? Maybe it's time to get my pilot's license[:)]!
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I believe there is a fault that runs up past Calgary, however the pressures here are minor resulting in very little slip when movement occurs. This results in very low magnitude earthquakes (perhaps 3 on the Richter scale).
The major area of earthquakes are seen off the West Coast on a fault running parallel to the coast. Quakes greater than 6.5 are a common occurence here. You may think that because these are not on land you are safe, in fact its just as dangerous.
Sudden slippage of the two sides of the fault can cause a displacement of water equivalent to that of the rock moved. Such movements can form Tsunamis which can travel undetected to the shore before causing havoc! These are common in Japan which sits on a triple-plate junction (in fact it is one of the most dangerous places in the world to live).
While we are on the subject of destruction, watch out for Mexico City during the next earthquake. It will be one of the catastrophes of this century. The current status of the city sees large numbers of buildings standing condemned after the last quake yet they cant be pulled down due to poor families moving in to squat. The City is built on poorly consolidated old lake sediments, when a quake occurs, these take on liqiud properties (liquifacation)and buildings actually sink. Many people in the damaged buildings will die in the next quake which i'd say isn't that far off.
Thats Economics...
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How sad that so many people will die because of poverty[V].
I remember hearing a quote that was something like "one poor man shames us all"[:I]. Does anyone know the exact quote or who said it?
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We've had some minor earthquakes in the UK lately, including one near Dudley that did quite a lot of damage. What is the origin of these ?
Chris
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well i'm sure you're aware that Britain is a long way from any plate boundaries (usual site for quake activity). However, you do not need to be near a plate boundary for a tremor to occur. Britain is inundated with faults and these are the usual sources of these minor earthquakes. (~300 earthquakes are detected in the UK every year).
The quake will result from pressures building in the brittle crust along these fault plains and then being released in a sudden event.
The fact Britain is not proximal to any plate boundaries means crustal pressures are considerably lower hence we only get magnitudes of about 2 or 3 (leading to minor local structural damage). The largest ever quake measured here i believe was in Colchester, Essex which led to church destruction.
The reason such a small quake caused damage to buildings in Dudley is that we don't build to withstand them. It may seem strange that Americans build their houses out of wood, bu this is often their saving grace as wood is considerably more maleable than concrete or bricks meaning it absorbs more of the frequency waves of the quake.
hope this helps.
Thats Economics...
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The mega tsunami will be triggered by an unknown number of eruptions at a island before it triggers a landslide n forms a 500 over m mega tsunami to crush the east of north america.
5-6 hr might not be enough time to evacuate everybody but it might be able to save thousands of life.
How i know this is because i watched a show called:"horizon",or else i would have learned it just today.
In the show they showed the mega tsunami striking the east of north america an that area was a sea of tall buildings poking up of the ocean only. There will be no survivors from that mega tsunami.
They said that Miami will be badly affected I think i dont really know much abou the countries affected by the mega tsunami.
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chris you say that the wave is 1720 feet high
THATS impossible the sea isnt deep enough
if true give me the proof[}:)]
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[^][:(][xx(][^]the largest wave eva wittnessed and surfed was only 300ft high [}:)][8D][;)][V][|)][?][:(][}:)][}:)]
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[:o)][;)][8D][:D]LAIR!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!![:(][8)]
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quote:
Originally posted by mad maXX
chris you say that the wave is 1720 feet high
THATS impossible the sea isnt deep enough
if true give me the proof[}:)]
Mad MaXX...of course the sea is deep enough, in some cases it's deeper than Mount Everest is high...that's well over 30,000 feet !!...in fact I think the deepest is reported at 37,000 feet....get your facts right before calling people liars !!
'Men are the same as women...just inside out !'
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....for instance...check this recent article out about life being found at over 37,000ft deep http://science.news.designerz.com/single-cell-organisms-found-in-ocean-depth.html and this one http://news.bbc.co.uk/1/hi/sci/tech/4235979.stm
'Men are the same as women...just inside out !'
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It doesn't matter how deep the ocean is, most tsunami's out in the ocean don't look like much, its only when they reach the shore line when the depth and energy of the wave causes it to "break" into something high above sea level, since there is less depth of water to accommodate it, but still the same amount of energy.
wOw the world spins?
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The question is less one of the size of the wave than the capacity of the shoreline to dissipate the energy. This is a factor of gradient (a slight gradient will reflect less energy back out to sea, which is what saved Bangla Desh) and resistance: we may yet have reason to thank NY for its skyscrapers, although trees appear to be even better at absorbing such forces. Perhaps it's time we stopped building on the shoreline and planted trees instead, a bit of a walk to the shore will do us good anyway...
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The highest tsunami was 524m in USA on 9 July 1958. Caused by a landslide too. Same as the one chris said.