Depends on where you live I suppose. If part of the volcano in the Azores lets go, albeit from one of the doom and gloom documentaries, the tidal wave could be well over 100 feet all along the east coast of the US. One person o nthe program asserted that some parts of the tsunami could go over lower parts of the Appalachian Mountains. I suppose they meant through the passes. Of course, if a large asteroid, which is apparently overdue, hits Earth, the tidal waves could be measured in miles above sea level. Overdue is also the Yellowstone Caldera blowing up, etc.