The northeastern Japanese coastal city of Sendai was devastated by a tsunami triggered by an earthquake with an 8.9 magnitude on March 10, 2011. Live footage inundated news outlets with images of the ocean moving inland, carrying houses, cars and other debris. Witnesses and viewers were stunned by a giant whirlpool moving with the tide across what was once dry land. Whirlpool formation following a tidal wave is not unusual, according to retired seismologist Ruth Ludwin. Interaction between the topography of the coastline and ocean floor combined with rushing water create the circular motion of the whirlpool.
The Naruto Strait whirlpool, located between the Seto Inland Sea and the Pacific Ocean, is formed by water rushing through the narrow strait four times a day. Water moving in both directions creates counter-currents that form the vortex. The Naruto whirlpool is the third-fastest on record, with recorded speeds of up to 12.4 mph with a vortex of approximately 65 feet in diameter.
Old Sow, located between Maine and New Brunswick, contains the largest whirlpool in the Western Hemisphere. In addition to whirlpools, Old Sow is made up of several other tidal phenomena including spouts and gyres. The Old Sow whirlpools form as water rushes through a narrow passageway made up of trenches and a mountain located 119 feet below the sea's surface. Other currents mix with the rapidly flowing water to create vortices and funnels. Tidal dams, storm surges and strong winds also fuel the formation of Old Sow whirlpools. Old Sow's diameter is approximately 7 miles in diameter with individual whirlpools within Old Sow's boundaries measuring 250 feet across.
Located near the Lofoten islands in Norway, the Lofoton Maelstrom was formed 20,000 years ago from opposing currents from waters moving through a marine channel and strong tidal currents from the Norwegian Sea. The powerful whirlpool, also referred to as a maelstrom, measures 2.5 miles wide. The depth of the Lofoten whirlpool is estimated from 130 to 195 feet deep.
Formed around 4,200 years ago, the Niagara Whirlpool is situated at the base of Niagara Falls in the Saint David's Buried Gorge. Rushing river water travels through the narrow passage of the Niagara Gorge mixes with forceful rapids and crashes against the solid rock basin of Niagara Glen to form the whirlpool. The whirlpool's flow normally runs counterclockwise, but when the river's flow is diverted to power plants, the whirlpool's direction reverses and runs clockwise.
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