This URL has a paper which delves into some detail the assumptions used in the forecasts for Very Large Tsunami effects. Specifically, Kilauea and La Palma. http://www.drgeorgepc.com/TsunamiMegaEvaluation.html "The recent numerical studies (Ward & Day, 2001; Ward 2001) forecasting mega tsunami generation from recurrences of large massive volcanic island flank failures, are based on unrealistic assumptions of present slope instability of Cumbre Vieja on La Palma and Kilauea in Hawaii, of source dimensions, of speed of failure, and of tsunami coupling mechanisms. Incorrect treatment of input parameters and of wave energy propagation and dispersion, produced incorrect estimates of near and far field terminal effects - thus overstating the tsunami threat." To summarize, the size of the likely drop, the speed with which it would most likely happen and other factors, including the short wave period, which tends to fade out at distance, argues that the effects would not be nearly as catastrophic as the popular press has reported. Reading the paper will give you a better idea of what is involved. Note that the geological record, even of recent events does not tend to support the wild predictions. The paper has details about this aspect of the problem. Very interesting reading. Mike Capt. Mike Maurice Tualatin(Portland), Oregon