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"Dave" wrote in message ... A recent article I read somewhere said that if the predicted bit of La Palma falls off in one slab the resulting tsunami will lead to the disappearance of the Isles of Scilly (among other damage!) Charlie Pridham writes Lots of people have said that, but it seems unlikely. To create a tsunami requires a high energy shock wave, a bit of land falling in would, however large not be moving fast enough for the damage to be transmitted any distance, although there would certainly be a large wave locally much as when large icebergs break off. I think you confuse speed with energy. If you drop a very very large mass (say 5000 million tons) a few hundred feet (and I think in the case of the canaries it drops a long way down to the ocean floor) then the *energy* released is converted into a (relatively) smaller mass of water travelling *very* fast. I don't know what the conversion factor is but say 1% of the mass travelling at say 20 times the speed would still be quite significant. -- David I may be wrong but I am not confused! :~) once the rock mass was in the water the effect would be slight however far it falls, it can after all only fall and accelerate at 9.81m/s2 . and I still think you would be hard pressed to even detect it in New York were it to happen, (a similar sized lump arriving from space would be travelling at a much higher speed and would indeed cause allsorts of problems were it to hit ocean). The movement of a tectonic plate can in some instances be at very high speed coupled with the total mass on the move gives a huge amount more energy and even then not all underwater quakes produces these waves. -- Charlie, gardening in Cornwall. http://www.roselandhouse.co.uk Holders of National Plant Collection of Clematis viticella (cvs) |
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"Charlie Pridham" wrote in message ... "Dave" wrote in message ... A recent article I read somewhere said that if the predicted bit of La Palma falls off in one slab the resulting tsunami will lead to the disappearance of the Isles of Scilly (among other damage!) Charlie Pridham writes Lots of people have said that, but it seems unlikely. To create a tsunami requires a high energy shock wave, a bit of land falling in would, however large not be moving fast enough for the damage to be transmitted any distance, although there would certainly be a large wave locally much as when large icebergs break off. I think you confuse speed with energy. If you drop a very very large mass (say 5000 million tons) a few hundred feet (and I think in the case of the canaries it drops a long way down to the ocean floor) then the *energy* released is converted into a (relatively) smaller mass of water travelling *very* fast. I don't know what the conversion factor is but say 1% of the mass travelling at say 20 times the speed would still be quite significant. -- David I may be wrong but I am not confused! :~) once the rock mass was in the water the effect would be slight however far it falls, it can after all only fall and accelerate at 9.81m/s2 . That is quite wrong. The rock hits the water quite fast, with a large amount of energy. As it sinks in the water, it gives its enrergy to the water, spreadover a large range in depths. These are just what is neded to excite a deep water wave. and I still think you would be hard pressed to even detect it in New York You could not be more wrong on this issue if you tried. Please desist from making qualitative speculations from the side lines. As has been said before, there are actually model experiments being performed under conditions where the scaling laws are known. The results from those are more important than your wishful thinking. were it to happen, (a similar sized lump arriving from space would be travelling at a much higher speed and would indeed cause allsorts of problems were it to hit ocean). The movement of a tectonic plate can in some instances be at very high speed coupled with the total mass on the move gives a huge amount more energy and even then not all underwater quakes produces these waves. Franz |
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