Earthguide animated diagram - Waves

The motion of seiche
The word seiche is pronounced "saysh." The waves in a seiche are stationary in the horizontal plane and do not progress forward. The waves move up and down, but not forward like wind waves at sea. That's why these waves are called as standing waves rather than progressive waves. The nodes are locations where no vertical motion occurs. Seiches occur most frequently in enclosed or semi-enclosed basins such as lakes, bays, harbors and bathtubs.	They can be triggered in an otherwise still body of water by strong winds, changes in atmospheric pressure, earthquakes, tsunami or tides. Triggering forces that set off a seiche are most effective if they operate at specific frequencies relative to the size of an enclosed basin. The definition of seiche requires some explanation. This the official definition from U.S. Army Corps of Engineers:	"(1) A standing wave oscillation of an enclosed waterbody that continues, pendulum fashion, after the cessation of the originating force, which may have been either seismic or atmospheric. (2) An oscillation of a fluid body in response to a disturbing force having the same frequency as the natural frequency of the fluid system. Tides are now considered to be seiches induced primarily by the periodic forces caused by the Sun and Moon. (3) In the Great Lakes area, any sudden rise in the water of a harbor or a lake whether or not it is oscillatory (although inaccurate in a strict sense, this usage is well established in the Great Lakes area)."