When it reaches a height sufficient to surmount the water already occupying the arm, it breaks over and comes rolling with a steep, high front. Some of the other famous tidal bores in the world occur in Canada's Bay of Fundy, in the Seine River of France, and in the Amazon River. A tidal wave, as such, is a catchall phrase connoting nothing more nor less than an unusual rise or incursion of water along the seashore. These can be attributable to a variety of factors such as offshore winds, storms or a combination of winds and spring tides. However, the term is often confused with that scourge of old movies and modern civilization alike, the tsunami.
Tsunamis have several remarkable features.
It is only when they begin to encounter shallow water that they begin to pile up into the monstrous waves that are responsible for the destruction that is attributed to them. The Aleutian chain is probably the most prolific producer of the tsunamis in the world. In the memory of most Alaskans, the tsunami associated with the 1964 earthquake is probably the most vivid. However, the Aleutian-generated tsunami of this century which probably had the most profound effects outside the state occurred on April 1, 1946. This resulted from an earthquake at Unimak Island.