Talk in an earth science class. The professor is talking about tsunamis. The term tidal wave is often inaccurately used for a tsunami. Soon, armies have nothing to do with the action of tides. A more accurate term is seismic sea wave. There has to be a disturbance of the earth's crust to produce a tsunami. Large earthquakes with epicenters under or near the ocean are the cause of most tsunamis. Volcanic eruptions and undersea landslides are also responsible. But unless accompanied by movements of the ocean floor, their effects are usually localized. Possibly this was true about the eruption of krakatau in eighteen eighty three, as soon army was responsible for most of the deaths caused by crack at our yet this soon army did not sink any ships. It did wash away several coastal villages and kill more than thirty six thousand people. Tsunamis work in complex ways. Some pounce on coastal settlements, like large breakers. Others produce a gentle wave that floats buildings off their foundations. But then a violent backwash may sweep buildings and people out to sea. The tsunami that wrecked hilo, hawaii, in nineteen forty six was so forceful, it folded parking meters. It caused needless deaths. When people return to save their belongings and got caught between waves, the deeper the water.