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

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