When rising and falling, the tides often produce circular currents, known as eddies, and some of them cause a downward pressure called a eddy.
Swirls can occur in different places: in the open sea, on the coast, that is, there is no specific rule. But it is possible to make a prediction of where this phenomenon will arise, in general, this phenomenon occurs in tropical areas due to the intense heat that interferes with the temperature of the oceans.
The great cause of eddies is the encounter of a portion of heated water with other cooler surroundings. These waters are at a mild temperature (less hot) due to cloud shadows, for example.
For a whirlpool to occur, several factors are needed:
- The average heating water temperature must be around 26°C. Water becomes lighter at this temperature and increases its evaporation level;
- The so-called low pressure areas come into being, because the air is different on these surfaces;
- The wind in these areas blows in circular motions. Hence, the whirlpool in the sea is formed.
Swirls generally occur at sea off the coast of Japan, Norway, the United States and Scotland. A 75m diameter whirlpool has already been recorded in Old Sow, USA. Whirlpools at sea don't have enough power to turn a boat, but the whirlpool can easily drown a swimmer or diver.
A famous example is the Naruto whirlpool, in Japan, it happens in the channel that connects the Inland Sea of Seto to the Pacific Ocean, it has the third fastest current in the world, at 20 km/h. The whirlpool occurs 4 times a day and attracts the attention of observers and tourists.
Swirls can also occur in rivers and lakes, but not under the same circumstances as the seas. In this case, what interferes in the formation of this phenomenon is the bottom of rivers, especially those with many depressions, stones and holes in the sand.
For a whirlpool to happen in a river, for example, there must be a “sink”, that is, a place (a point) that absorbs water. This region is located at the bottom of the river and works as a bathtub drain, where water is sucked into its interior. And it was precisely this phenomenon that occurred with Commander Sales' boat, which caused the death of 40 people in May (2008). The boat was engulfed by the waters of the Solimões River, in the Amazon.
By Líria Alves
Brazil School Team
Curiosities - Brazil School
Source: Brazil School - https://brasilescola.uol.com.br/curiosidades/a-formacao-redemoinhos.htm
