By David Murphy
A tsunami is a large ocean wave usually created by the shock from an underwater earthquake. The quake causes the lay of the ocean floor to change suddenly, sending enormous shock waves through the water, which in turn generate the tsunami wave. Earthquake-caused landslides at the edge of an ocean basin can also trigger a tsunami.
Tsunamis, when they encounter a coastline, can cause extensive damage and flooding.
Tsunami is a Japanese word meaning harbor waves. This is no surprise, since Japan has the best-recorded history of tsunamis and a tsunami grows to its greatest height and does the most damage in enclosed areas like harbors.