Whirlpool

Whirlpool, body of water spinning in a generally circular motion, often around a central depressed area and occasionally around a vortical cavity that draws surrounding floating objects toward the center. Whirlpools at sea are caused by the meeting of opposing currents and tides, by ocean currents striking offshore rocks and other coastal configurations, and by the force of wind acting upon water. Irregularities in basin and channel bottoms usually cause whirlpools in rivers and lakes.

Whirlpools in the open seas are giant suctionless eddies, such as the Sargasso Sea in the Atlantic Ocean, and pose no threat to modern shipping. Earlier sailing ships, however, were sometimes becalmed in them and were held fast in their centers or were swept by the slowly rotating currents against rugged coasts. Whirlpools with a strong vortical motion, on the other hand, can become very violent and are capable of sucking boats into their rapidly down-spiraling cavities. Noted whirlpools include the Charybdis (see Scylla and Charybdis) in the Strait of Messina between mainland Italy and the island of Sicily, the Maelstrom, or Moskenstraumen, in the Lofoten Islands off Norway, and the Whirlpool Rapids below Niagara Falls.