Tsunami:   n. a very large ocean wave caused by an underwater earthquake or volcanic eruption: also loosely called ‘tidal wave’.

        When a tidal wave is in the open ocean, it can and fall several feet. Some ships let tidal waves pass undetected because it takes 10 to 30 minutes to rise. When a tidal wave is about to collide with the coast it can reach up to 100 feet high. Seismic waves are under the sea and can cause a tidal wave. Sometimes scientists can predict when a tidal wave will reach shore so civilians can evacuate the area. Seismic waves can travel a lot faster than tidal waves can travel. In the Pacific Ocean a tidal wave can travel up to 600 mph. When a tidal wave enters the shore its speed drops down to 100 mph.