A satrange phenomenon of a natrual whirlpool in the ocean Definition of a whirlpool A rapid circular current of liquid. [syn: vortex, maelstrom] A vortex is any whirlpool with a downdraft. A maelstrom is the term applied to the most powerful whirlpools. The most powerful "natural" whirlpools are the result of tidal changes and the resulting fast-flowing water through narrow shallow straits. But most people are more familar with smaller less dangerous whirlpools that occur in streams or at the bottom of waterfalls. To be sure, these whirlpools can cause lots of problems for watercraft, and they can pull people down and not let them up. So they are dangerous, but not to the scale of a maelstrom whirlpool that can swallow a boat. How do whirlpools form? Any time water flows through a narrow path, it forms at least a partial whirlpool. As the water passes through the narrower opening, it accelerates and forms a more powerful force. If the downstream area then enlarges, it can mature into a complete whirlpool. As water is pulled into an opening by gravity, it begins to spin. (See below for more information about the direction it spins.) Once this begins, it intensifies and forms a cavity in the center of the drain. The cavity creates a vacuum into which objects such as bubbles, water molecules, and other floating objects are pulled. As these objects are "sucked" into the vortex, the centrifugal (outward) force maintains the hole in the middle through which air passes. What makes whirlpools spin? As the water is pulled down into the opening, the water particles fight for the smaller space and push each other to the side. This pushing and nudging by itself would not necessarily cause the water to spin, especially in a perfectly-shaped funnel and no other directional influence on the water. But a perfectly-shaped funnel never exists in nature. There are inconsistently-shaped rocks or other obstructions that force the water away from them. This initiates a spinning motion that accelerates as the water is pulled by gravity. What gives whirlpools their vortex shape? As the water spins and accelerates, the centrifugal force tries to force it to the outside. Of course, it is contained by the rocks or other naturally-occuring obstructions, so it cannot "fly out" of the natural funnel. Water is heavier than air, so the center of the vortex creates a column of air which is simply the vacancy caused by the water being forced to the side.