The phenomenon of Chalkida
One thing that characterizes Euboea and especially Chalkida is the phenomenon of "trela nera". (i.e. Crazy Waters). This phenomenon is a rare phenomenon that occurs in the Strait of Euripus under the bridge opening, where the flow of ocean waters changes. That is, when the water flowing one direction and then in the exact opposite direction. This change happens approximately every 6 hours.This phenomenon reaches its climax under the old sliding bridge where the speed of the water takes the maximum speed of 9 miles per hour. It is said that this speed of the water, a shark will struggle to swim in the opposite direction. This phenomenon is as follows: the waters move in the one direction for 6 hours, then for 8 minutes waters are stable and then they flow in the opposite direction for other 6 hours, then other 8 minutes the water is stable, and so on. It is this strange phenomenon that has given the city of Xalkida the nickname of "Crazy waters".
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Explanations for this phenomenon
The explanation of this phenomenon of Euripus has bothered the ancient Greeks, especially Aristotle and Eratosthenes and many other scientists of the last century, including the Greek Dimitrios Eginitis. But the explanation has been given and has now become acceptable. Is that natural tidal wave reaching the Aegean Sea on Evoia east part of entering the North Evoia and another enters the South Evian. Due to the different length of the route, while natural tidal wave coming from the south reaches the channel of Euripus in 1 hour and 15 minutes earlier than coming from the north. From this, it is normal southerly entering water bodies where elevates the level of 30–40 cm and sea generated from N. to B. After 6 hours, as the successor to ebb tide, the conditions are reversed and created oncoming, in the Northern part of after accumulated larger bodies of water. When we happen nerves, so the intensity is high tide, the tide of Euripus presented normal. But in quartered, where the water is weaker, so the configuration of the seaside, the ocean floor, the current weather conditions and other barometric causes that water occurs irregularly.
2 global singularities
What is not widely known, however, is that this phenomenon exists in other parts of the world has 2 global singularities.
The first is the fact that the 24th hour of the third and last day of each period clutter (i.e. the 9 and 23 day Moon) the water always begin to flow from the North to the South Evian Gulf.
The second unique global phenomenon is that the equinox periods (i.e. 21 March and 22 September) the currents change direction immediately without staying 8 minutes like made all other days.