{"id":68,"date":"2014-03-13T21:41:02","date_gmt":"2014-03-13T21:41:02","guid":{"rendered":"http:\/\/antonios-antoniou.gr\/en\/?page_id=68"},"modified":"2014-11-06T11:17:03","modified_gmt":"2014-11-06T11:17:03","slug":"tides-and-the-euripus-phenomenon","status":"publish","type":"page","link":"https:\/\/www.antonios-antoniou.gr\/en\/tides-and-the-euripus-phenomenon","title":{"rendered":"Tides and the Euripus phenomenon"},"content":{"rendered":"

Hellenic<\/b> Republic<\/b><\/b><\/p>\n

Municipality<\/b> of Chalkida<\/b><\/b><\/p>\n

The Home of Knowledge and Science in Chalkida\u00a0<\/b><\/p>\n

\"estia-logo\"<\/a><\/p>\n

\u00a0Tides and the Euripus phenomenon<\/b><\/h3>\n

 <\/p>\n

Dr. Antonios Antoniou<\/i><\/b>
\nPhD in Astrophysics<\/i><\/b>
\n\u00a0University of Athens<\/i><\/b><\/p>\n

\u00a0<\/i><\/b><\/p>\n

Everybody can observe that every 6 hours the sea water rises (flood) and in the next 6 hours it goes down again (ebb). We have a period of 12 <\/b>h <\/b>or 4 phases in<\/b> 24h 50min 30sec. <\/b>The 50 min and 30 sec difference from the \u201c24 hours\u201d refers to the Moon, because the Moon needs exactly this period of time to pass over the same place on Earth twice (Newton 1687).<\/p>\n

Let\u2019s assume that the Earth was still <\/b>and consisted of sea water. Then, the Moon would create an enormous wave that would follow it to its rotation around the Earth (see Figure 1).<\/p>\n

But reality is different. The Earth surface consists of continents and so this hypothetical high tide wave is blocked and moves otherwise. The coasts and the morphology of the sea\u2019s bottom contribute to the development of the phenomenon in different ways.<\/p>\n

The Sun contributes to the tide phenomenon. The tide force depends on the position of the three bodies (Sun, Earth and Moon). This force is stronger in the new moon phase and milder in the squaring phase (see Figure 2).\u00a0 The ratio of the earth\u2019s tide force to the sun\u2019s tide force is about 2.2. This means that the moon is mainly responsible \u2013 for the flood \u2013 ebb phenomenon. The sun contribution is at most 28%.\u00a0 <\/b><\/p>\n

If we define as Height <\/b>the highest flood minus the lowest ebb then at the Mediterranean coasts the height is about 25 cm, in extra cases 45 cm, at North Africa coasts it is about 1 m, in the Bay Fundy in Canada about 15.4 m and in the English Channel <\/b>about <\/b>15m.<\/p>\n

\"\"<\/p>\n

Figure1: The tide phenomenon in ideal case<\/pre>\n
\"figure2\"<\/a><\/p>\n
Figure 2: The Sun contribution to the tide phenomenon<\/pre>\n
The Euripus phenomenon<\/b><\/p>\n
The Euripus Channel has width 39m, length\u00a0 40m,depth=8.5m, latitude \u03c6=38\u00b0 27\u0384 \u039d and longitude \u03bb=24\u00b0 00\u0384 E (Figure 3).<\/p>\n
A continuous motion of water is observed with a periodical change of its flow. The phenomenon is more intense in the conjunctions (Sun \u2013 Earth \u2013 Moon angle = 180 degrees) while in the squaring (Sun \u2013 Earth \u2013 Moon \u2013 90 degrees) it is milder. The speed which has been measured is about 5-6 mil\/h. and sometimes 9 mil\/h.<\/p>\n
\"xal1\"<\/a><\/p>\n
Figure 3: The Euripus Channel<\/pre>\n
Characteristics of the phenomenon<\/b><\/p>\n
a<\/b>) <\/b>Regular stream<\/b>:<\/b><\/p>\n
It is observed 22-23 days of the month. 11-12 days is during the new moon phase and 11 \u2013 12 during the full moon phase. The flow goes from South to North for 6 <\/b>hours<\/b> and from North to South for the next 6 <\/b>hours<\/b>. There is a period of 12 h (like the flood \u2013 ebb phenomenon) or 4 <\/b>changes<\/b> in a period of time of about 24 h and 50 min.<\/p>\n
b<\/b>) <\/b>Irregular stream<\/b>:<\/b><\/p>\n
It lasts <\/b>about 6 days (3 during the first squaring and 3 during the last squaring).<\/p>\n
Its characteristic is an <\/b>irregular change of the stream (about 14 changes per 24 hours).<\/p>\n
This irregular stream is a result of the mild indication of the phenomenon.<\/p>\n
<\/b>Explanation<\/b><\/p>\n
The big tidal wave is created by the gravitation of the Moon in the East Mediterranean and is directed towards the west. When it reaches the South Aegean it heads north and arrives in the east coast of Evoia almost three hours after the moment the Moon passes the meridian of Halkida. However, the wave entering the SouthEvoikosBay reaches the Euripus channel 1 hour and 15 minutes earlier than the one entering the NorthEvoikosBay because the route is shorter. Moreover, the volume of the sea water of the south wave is bigger than the volume of the north wave because the north one is obstructed by the strait of north Evoia. So, when the south wave arrives in Euripus we notice a rise in the level of water in the south part of the channel, which goes up to 30-40 cm. This rise in the water level is the cause of the flow of water from the South to the North Evoikos bay. Six hours later conditions are reversed because in the meantime the wave entering the North Evoikos bay reaches the channel and the water level rises in the north part. As a result the stream is reversed. The period of 22 hours and 22 minutes has to be attributed to the shaping of the shore of the two sides of Evoikos bay (North and South) (see Figure 4).<\/p>\n
\"figure4\"<\/a><\/p>\n
Figure 4:<\/b> The big tidal wave is created by the gravitation of the Moon in the East Mediterranean and is directed towards the west.\u00a0 The wave entering the SouthEvoikosBay reaches the Euripus channel 1 hour and 15 minutes earlier than the one entering the NorthEvoikosBay because the route is shorter. When the south wave arrives in Euripus we notice a rise in the level of water in the south part of the channel, which goes up to 30-40 cm. This rise in the water level is the cause of the flow of water from the South to the North Evoikos bay. Six hours later conditions are reversed because in the meantime the wave entering the North Evoikos bay reaches the channel and the water level rises in the north part. As a result the stream is reversed.<\/pre>\n
Who studied the phenomenon?<\/b><\/p>\n
The first who found out the cause of the phenomenon was Aristotle (<\/b>384 \u2013 322 B.C.)<\/p>\n
and Eratosthenes (275-195 B.C). The phrase \u00ab<\/b>\u03b4\u03b5\u03cd\u03c1\u03bf<\/b> <\/b>\u03ba\u03b1\u03ba\u03b5\u03af\u03c3\u03b5<\/b> <\/b>\u03c4\u03c9\u03bd<\/b> <\/b>\u03c0\u03bf\u03c1\u03b8\u03bc\u03ce\u03bd<\/b> <\/b>\u03c4\u03b1\u03bb\u03b1\u03bd\u03c4\u03b5\u03cd\u03b5\u03c3\u03b8\u03b1\u03b9<\/b> <\/b>\u03c4\u03b7\u03bd<\/b> <\/b>\u03b8\u03ac\u03bb\u03b1\u03c4\u03c4\u03b1\u03bd<\/b> <\/b>\u03c0\u03bf\u03bb\u03bb\u03ac\u03ba\u03b9\u03c2<\/b>\u00bb<\/b> is attributed to Aristotle. Strabo attributes the phrase <\/b>\u00ab<\/b>\u03cc\u03c4\u03b9<\/b> <\/b>\u03b7<\/b> <\/b>\u03b5\u03c6<\/b> <\/b>\u03b5\u03ba\u03ac\u03c4\u03b5\u03c1\u03b1<\/b> <\/b>\u03b8\u03ac\u03bb\u03b1\u03c4\u03c4\u03b1<\/b> <\/b>\u03ac\u03bb\u03bb\u03b7\u03bd<\/b> <\/b>\u03ba\u03b1\u03b9<\/b> <\/b>\u03ac\u03bb\u03bb\u03b7\u03bd<\/b> <\/b>\u03b5\u03c0\u03b9\u03c6\u03ac\u03bd\u03b5\u03b9\u03b1\u03bd<\/b> <\/b>\u03ad\u03c7\u03b5\u03b9<\/b>\u00bb<\/b> to Eratosthenes. Both phrases indicate the tide as the cause of the phenomenon.<\/p>\n
But the final solution was given by professor Dimitrios Aiginitis who relied on the material of the former researchers. It is the explication we mentioned before.<\/p>\n
Why Euripus<\/b>?<\/b><\/p>\n
The word \u201cEuripus\u201d consists of the words \u03b5\u03c5 + \u03c1\u03b9\u03c0\u03ae (brash flow). The terminology Euripus is used internationally to signify streams with a strong rush.<\/p>\n
Can we calculate the direction of the stream?<\/b><\/p>\n
We can estimate the flow of the stream provided we are not found in the squaring phases when there is total disorder. The port authorities of Halkida issue an information leaflet which includes the direction of the streams for a lunar (synodical) month (Table 1).<\/p>\n
Table 1:\u00a0The direction of the streams for a lunar (synodical) month (Port Authority of Chalkida)<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
<\/td>\nN-S<\/b><\/td>\nS-N<\/b><\/td>\nS-N<\/b><\/td>\nS-N<\/b><\/td>\n<\/tr>\n
New Moon<\/b><\/td>\n02.30-8.48<\/td>\n8.50-14.43<\/td>\n14.45-21.04<\/td>\n21.06-02.58<\/td>\n<\/tr>\n
1<\/td>\n03.00-09.18<\/td>\n09.20-15.13<\/td>\n15.15-21.34<\/td>\n21.36-03.28<\/td>\n<\/tr>\n
2<\/td>\n03.30-09.48<\/td>\n09.50-15.43<\/td>\n15.45-22.04<\/td>\n22.06-02.58<\/td>\n<\/tr>\n
3<\/td>\n04.00-10.18<\/td>\n10.20-16.13<\/td>\n16.15-22.34<\/td>\n22.36-04.28<\/td>\n<\/tr>\n
4<\/td>\n04.30-10.48<\/td>\n10.50-16.43<\/td>\n16.45-23.04<\/td>\n23.06-04.58<\/td>\n<\/tr>\n
5<\/td>\n05.00-11.18<\/td>\n11.20-17.13<\/td>\n17.15-23.34<\/td>\n23.36-05.28<\/td>\n<\/tr>\n
6<\/td>\n05.30-11.48<\/td>\n11.50-16.43<\/td>\n16.45-00.04<\/td>\n00.06-05.58<\/td>\n<\/tr>\n
7<\/td>\nIrregular stream<\/b><\/td>\n<\/tr>\n
10<\/td>\n00.01-06.18<\/td>\n06.20-12.13<\/td>\n12.15-18.34<\/td>\n18.36-00.28<\/td>\n<\/tr>\n
11<\/td>\n00.30-06.48<\/td>\n06.50-12.43<\/td>\n12.45-19.04<\/td>\n19.06-00.58<\/td>\n<\/tr>\n
12<\/td>\n01.00-07.18<\/td>\n07.20-13.13<\/td>\n13.15-19.34<\/td>\n19.36-01.28<\/td>\n<\/tr>\n
13<\/td>\n01.30-07.48<\/td>\n07.50-13.43<\/td>\n13.45-20.04<\/td>\n20.06-01.58<\/td>\n<\/tr>\n
14<\/td>\n02.00-08.18<\/td>\n08.20-14.13<\/td>\n14.15-20.34<\/td>\n20.36-02.28<\/td>\n<\/tr>\n
Full Moon<\/b><\/td>\n02.30-08.48<\/td>\n08.50-14.43<\/td>\n14.45-21.04<\/td>\n21.06-02.58<\/td>\n<\/tr>\n
16<\/td>\n03.00-09.18<\/td>\n09.20-15.13<\/td>\n15.15-21.34<\/td>\n21.36-03.28<\/td>\n<\/tr>\n
17<\/td>\n03.30-09.48<\/td>\n09.50-15.43<\/td>\n15.45-22.04<\/td>\n22.06-03.58<\/td>\n<\/tr>\n
18<\/td>\n04.00-10.18<\/td>\n10.20-16.13<\/td>\n16.15-22.34<\/td>\n22.36-04.28<\/td>\n<\/tr>\n
19<\/td>\n04.30-10.48<\/td>\n10.50-16.43<\/td>\n16.45-23.04<\/td>\n23.06-04.58<\/td>\n<\/tr>\n
20<\/td>\n05.00-11.18<\/td>\n11.20-17.13<\/td>\n17.15-23.34<\/td>\n23.36-05.28<\/td>\n<\/tr>\n
21<\/td>\n05.30-11.48<\/td>\n11.50-17.43<\/td>\n17.45-00.04<\/td>\n00.06-05.58<\/td>\n<\/tr>\n
22<\/td>\nIrregular stream<\/b><\/td>\n<\/tr>\n
25<\/td>\n00.01-06.18<\/td>\n06.20-12.13<\/td>\n12.15-18.34<\/td>\n18.36-00.28<\/td>\n<\/tr>\n
26<\/td>\n00.30-06.48<\/td>\n06.50-12.43<\/td>\n12.45-19.04<\/td>\n19.06-00.58<\/td>\n<\/tr>\n
27<\/td>\n01.00-07.18<\/td>\n07.20-13.13<\/td>\n13.15-19.34<\/td>\n19.36-01.28<\/td>\n<\/tr>\n
28<\/td>\n01.30-07.48<\/td>\n07.50-13.43<\/td>\n13.45-20.04<\/td>\n20.06-01.58<\/td>\n<\/tr>\n
29<\/td>\n02.00-08.18<\/td>\n08.20-14.13<\/td>\n14.15-20.34<\/td>\n20.36-02.28<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n","protected":false},"excerpt":{"rendered":"
Hellenic Republic Municipality of Chalkida The Home of Knowledge and Science in Chalkida\u00a0 \u00a0Tides and the Euripus phenomenon   Dr. Antonios Antoniou PhD in Astrophysics \u00a0University of Athens \u00a0 Everybody can observe that every 6 hours the sea water rises (flood) and in the next 6 hours it goes down again (ebb). We have a … Continue reading Tides and the Euripus phenomenon<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":85,"parent":0,"menu_order":0,"comment_status":"open","ping_status":"open","template":"page-templates\/full-width.php","meta":{"footnotes":""},"class_list":["post-68","page","type-page","status-publish","has-post-thumbnail","hentry"],"_links":{"self":[{"href":"https:\/\/www.antonios-antoniou.gr\/en\/wp-json\/wp\/v2\/pages\/68","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.antonios-antoniou.gr\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.antonios-antoniou.gr\/en\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.antonios-antoniou.gr\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.antonios-antoniou.gr\/en\/wp-json\/wp\/v2\/comments?post=68"}],"version-history":[{"count":13,"href":"https:\/\/www.antonios-antoniou.gr\/en\/wp-json\/wp\/v2\/pages\/68\/revisions"}],"predecessor-version":[{"id":119,"href":"https:\/\/www.antonios-antoniou.gr\/en\/wp-json\/wp\/v2\/pages\/68\/revisions\/119"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.antonios-antoniou.gr\/en\/wp-json\/wp\/v2\/media\/85"}],"wp:attachment":[{"href":"https:\/\/www.antonios-antoniou.gr\/en\/wp-json\/wp\/v2\/media?parent=68"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}