The are tidal whirlpool

Whirlpool

A whirlpool is a swirling body of water usually produced by ocean tides. The vast majority of whirlpools are not very powerful. More powerful ones are more properly termed maelstroms. Vortex is the proper term for any whirlpool that has a downdraft...

s in the Naruto Strait

Naruto Strait

is a strait between Awaji Island and Shikoku in Japan. It connects Harima nada, the eastern part of the Inland Sea and Kii Channel. A famous feature of the strait is the Naruto whirlpools. Ōnaruto Bridge, the southern part of Akashi-Kaikyo Bridge crosses over it....

, a channel

Channel (geography)

In physical geography, a channel is the physical confine of a river, slough or ocean strait consisting of a bed and banks.A channel is also the natural or human-made deeper course through a reef, sand bar, bay, or any shallow body of water...

 between Naruto

Naruto, Tokushima

is a city in Tokushima Prefecture, Japan.In the quinquennial census of 2010, the city had a population of 61,522 . With a total area of the population density is 454 persons per km².The city was founded on March 15, 1947....

 in Tokushima

Tokushima Prefecture

is a prefecture of Japan located on Shikoku island. The capital is the city of Tokushima.- Tokushima Prefecture and Myodo Prefecture :Long ago, Tokushima City belonged to a region known as Myōdō-gun...

 and Awaji Island

Awaji Island

is an island in Hyōgo Prefecture, Japan, in the eastern part of the Seto Inland Sea between the islands of Honshū and Shikoku. The island has an area of 592.17 km²...

 in Hyōgo

Hyogo Prefecture

is a prefecture of Japan located in the Kansai region on Honshū island. The capital is Kobe.The prefecture's name was previously alternately spelled as Hiogo.- History :...

, Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

.

The strait between Naruto and Awaji island has a width of about 1.3 kilometre (0.807784557644749 mi). The strait

Strait

A strait or straits is a narrow, typically navigable channel of water that connects two larger, navigable bodies of water. It most commonly refers to a channel of water that lies between two land masses, but it may also refer to a navigable channel through a body of water that is otherwise not...

 is one of the connections between the Pacific Ocean

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

 and the Inland Sea, a body of water separating Honshū

Honshu

is the largest island of Japan. The nation's main island, it is south of Hokkaido across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyushu across the Kanmon Strait...

 and Shikoku

Shikoku

is the smallest and least populous of the four main islands of Japan, located south of Honshū and east of the island of Kyūshū. Its ancient names include Iyo-no-futana-shima , Iyo-shima , and Futana-shima...

, two of the main islands of Japan. The tide moves large amounts of water into the Inland Sea twice per day, and also removes large amounts of water twice a day. With a range of up to 1.7 m (5.6 ft), the tide

Tide

Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....

 creates a difference in the water level of up to 1.5 m (4.9 ft) between the Inland Sea and the Pacific. Due to the narrowness of the strait, the water rushes through the Naruto channel at a speed of about 13–15 km/h (8.1–9.3 ) four times per day, twice flowing in and twice flowing out. During a spring tide, the speed of the water may reach 20 km/h (12.4 mph), creating vortices

Vortex

A vortex is a spinning, often turbulent,flow of fluid. Any spiral motion with closed streamlines is vortex flow. The motion of the fluid swirling rapidly around a center is called a vortex...

 up to 20 m (65.6 ft) in diameter.

The current in the strait is the fastest in Japan and the fourth fastest in the world after the Saltstraumen

Saltstraumen

Saltstraumen is a sound with a strong tidal current located in Nordland 30 km east of the city of Bodø, Norway. The narrow channel connects the outer Saltfjord with its extension, the large Skjerstadfjord. It is the strongest tidal current in the world...

 outside Bodø

Bodø

is a city and a municipality in Nordland county, Norway. It is part of the Salten region.The city of Bodø was established as a municipality on 1 January 1838 . Bodin was merged with Bodø on 1 January 1968. Skjerstad was merged with Bodø on 1 January 2005...

 in Norway

Norway

Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

, which reaches speeds of 37 km/h (23 mph), the Moskenstraumen off the Lofoten

Lofoten

Lofoten is an archipelago and a traditional district in the county of Nordland, Norway. Though lying within the Arctic Circle, the archipelago experiences one of the world's largest elevated temperature anomalies relative to its high latitude.-Etymology:...

 islands in Norway

Norway

Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

 (the original maelstrom

Maelstrom

A maelstrom is a very powerful whirlpool; a large, swirling body of water. A free vortex, it has considerable downdraft. The power of tidal whirlpools tends to be exaggerated by laymen. There are virtually no stories of large ships ever being sucked into a maelstrom, although smaller craft are in...

), which reaches speeds of 27.8 km/h (17.3 mph); and the Old Sow whirlpool in New Brunswick

New Brunswick

New Brunswick is one of Canada's three Maritime provinces and is the only province in the federation that is constitutionally bilingual . The provincial capital is Fredericton and Saint John is the most populous city. Greater Moncton is the largest Census Metropolitan Area...

, Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, which has been measured with a speed of up to 27.6 km/h (17.1 mph).

The whirlpools can be observed from ships, or from the Naruto Bridge spanning the strait. The suspension bridge has a total length of 1629 m (5,344.5 ft), with the center span over the strait having a length of 876 m (2,874 ft) and a height of 41 m (134.5 ft) above sea level. A good view is also possible from the shore on Awaji island.

External links

• Whirlpools: Experiencing Naruto Whirlpools, IAHR Newsletter, p.28-19, 2002
• Forum about schedule and tides