Whirlpool

A whirlpool (or maelstrom) is a body of rotating water produced by opposing currents or a current running into an obstacle. Small whirlpools form when a bath or a sink is draining. More powerful ones in seas or oceans may be termed maelstroms. Vortex is the proper term for a whirlpool that has a downdraft. In narrow ocean straits with fast flowing water, whirlpools are often caused by tides. Many stories tell of ships being sucked into a maelstrom, although only smaller craft are actually in danger. Smaller whirlpools appear at river rapids and can be observed downstream of manmade structures such as weirs and dams. Large cataracts, such as Niagara Falls, produce strong whirlpools. The Maelstrom of Saltstraumen is earth's strongest maelstrom. It is located close to the Arctic Circle, 33 km (20 mi) round the bay on Highway 17, south-east of the city of Bodø, Norway. The strait at its narrowest is 150 m (490 ft) in width and water 'funnels' through the channel four times a day. It is estimated that 400 million cubic metres (110 billion US gallons) of water passes the narrow strait during this event. The water is creamy in colour and most turbulent during high tide. It is often witnessed by tourists. It reaches speeds of 40 km/h (25 mph), with mean speed of about 13 km/h (8.1 mph). As navigation is dangerous in this strait only a short segment of time is available for large ships to pass through. Its impressive strength is caused by the world's strongest tide occurring in the same location during the new and full moon. A narrow channel of 3 km (2 mi) length connects the outer Saltfjord with its extension, the large Skjerstadfjord, causing a colossal tide which produces the Saltstraumen maelstrom. Moskstraumen is an unusual system of whirlpools in the open seas in the Lofoten Islands off the Norwegian coast. It is the second strongest whirlpool in the world with flow currents reaching speeds as high as 32 km/h (20 mph). It is mentioned by several books and movies. The Moskstraumen is formed by the combination of powerful semi-diurnal tides and the unusual shape of the seabed, with a shallow ridge between the Moskenesøya and Værøy islands which amplifies and whirls the tidal currents. The fictional depictions of the Maelstrom by Edgar Allan Poe, Jules Verne, and Cixin Liu describe it as a gigantic circular vortex that reaches the bottom of the ocean, when in fact it is a set of currents and crosscurrents with a rate of 18 km/h (11 mph). Poe described this phenomenon in his short story A Descent into the Maelstrom, which during 1841 was the first to use the word 'maelstrom' in the English language; in this story related to the Lofoten Maelstrom, two fishermen are swallowed by the maelstrom while one survives. The Corryvreckan is a narrow strait between the islands of Jura and Scarba, in Argyll and Bute, on the northern side of the Gulf of Corryvreckan, Scotland. It is the third-largest whirlpool in the world. Flood tides and inflow from the Firth of Lorne to the west can drive the waters of Corryvreckan to waves of more than 9 metres (30 ft), and the roar of the resulting maelstrom, which reaches speeds of 18 km/h (11 mph), can be heard 16 kilometres (9.9 mi) away. Though it was classified initially as non-navigable by the British navy it was later categorized as 'extremely dangerous'. A documentary team from Scottish independent producers Northlight Productions once threw a mannequin into the Corryvreckan ('the Hag') with a life jacket and depth gauge. The mannequin was swallowed and spat up far down current with a depth gauge reading of 262 metres (860 ft) with evidence of being dragged along the bottom for a great distance.