Energy required for a large tsunami There has been a recent panic regarding the volcano eruption on La Palma in the Canary Islands. That this volcano might cause a massive tsunami that would kill millions.
Wouldn't a 50 meter tsunami large enough to inundate the eastern seaboard require an immense amount of energy? Such as more than the energy of the collapse of a side of a mountain into the ocean?
The asteroid that is credited with the extinction of the dinosaurs had an estimated energy of 21 to 921 billion Hiroshima A-Bombs for example.

 A: My previous answer was fir the most part nonsense due to incorrect information on continental shelf topography. Here is s more accurate answer.
Water waves store half their energy as kinetic energy in the alternating currents. So to achieve a runup of 50m, we need a 25m wave.
The first obstacle that an approaching tsunami would encounter is the continental shelf, which is bounded by the Ice Age coast sunken under 149m of sea level rise. In the East Coast, this shelf extends about 65km on average.
Most of the shelf is less than 30m deep. Therefore, the tsunami needs a wavelength considerably larger than the width of this shelf in order to pass it without losing much of it's energy to breaking.
Based on the above, we can assume the following parameters as a minimum
Wavelength = 65km
Amplitude = 25m
Span = distance from La Palma × 2π = 40,000km
Wave energy = 2,500 × 65,000 × 40,000,000 × 25² = 4,062.5 quadrillion joules
Thus is the energy of 400 billion tons falling 2km. That amounts to between 67km³ and 133km³ of rock, assuming 100% efficiency
