Whirlpool

A whirlpool is a body of rotating water produced by opposing currents or a current running into an obstacle. Miniature whirlpools form when a bath or a sink is draining. More powerful ones formed in seas or oceans may be called maelstroms (/ˈmeɪlstrɒm, -rəm/ MAYL-strom, -⁠strəm). 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. Small whirlpools appear at river rapids and can be observed downstream of artificial structures such as weirs and dams. Large cataracts, such as Niagara Falls, produce strong whirlpools.

One of the earliest uses in English of the Scandinavian word malström or malstrøm was by Edgar Allan Poe in his short story "A Descent into the Maelström" (1841). The Nordic word itself is derived from the Dutch word maelstrom (pronounced [ˈmaːlstroːm] ^ⓘ; modern spelling maalstroom), from malen ('to mill' or 'to grind') and stroom ('stream'), to form the meaning 'grinding current' or literally 'mill-stream', in the sense of milling (grinding) grain.

Saltstraumen is a narrow strait located close to the Arctic Circle, 33 km (20 mi) south-east of the city of Bodø, Norway. It has one of the strongest tidal currents in the world. Whirlpools up to 10 metres (33 ft) in diameter and 5 metres (16 ft) in depth are formed when the current is at its strongest.

Moskstraumen or Moske-stroom 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). This is supposedly the whirlpool depicted in Olaus Magnus's map, labeled as "Horrenda Caribdis" (Charybdis).

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 Værøya islands which amplifies and whirls the tidal currents.

The fictional depictions of the Moskstraumen 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 Maelström", which in 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 km (10 mi) away. Though it was classified initially as non-navigable by the Royal Navy it was later categorized as "extremely dangerous".