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Amphidromic point

 

 
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Amphidromic point
 
 
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An amphidromic point is a point within a tidal system where the tidal range
Tidal range

The tidal range is the vertical difference between the highest high tide and the lowest low tide. In other words, it is the difference in height between high and low tides....
 is almost zero.

Amphidromic points occur because of the coriolis effect
Coriolis effect

In physics, the Coriolis effect is an apparent deflection of moving objects when they are viewed from a rotating reference frame.Newton's laws of motion govern the motion of an object in an inertial frame of reference....
 and interference
Interference

In physics, interference is the addition of two or more waves that result in a new wave pattern.Interference usually refers to the interaction of waves which are correlated or Coherence with each other, either because they come from the same source or because they have the same or nearly the same frequency....
 within oceanic basin
Oceanic basin

Hydrologically, an oceanic basin may be anywhere on Earth that is covered by seawater, but geologically ocean basins are large Basin that are below sea level....
s, sea
SEA

See also: Sea and seasThe three-letter acronym SEA may refer to:People/organizations/businesses*Scientists and Engineers for America, a pro-science political advocacy group....
s and bay
Headlands and bays

Headlands and bays are two related features of the coastal environment....
s creating a wave pattern — called an amphidromic system — which rotates around the amphidromic point. At the amphidromic point, there is almost no vertical movement. There can be tidal currents as the water levels on either side of the amphidromic point are not the same.

Based on the accompanying figure, the set of clockwise amphidromic points includes:

Anti-clockwise amphidromic points include:

The islands of Madagascar
Madagascar

Madagascar, or Republic of Madagascar , is an island nation in the Indian Ocean off the southeastern coast of Africa. The main island, also called Madagascar, is the List of islands by area, and is home to 5% of the world's plant and animal species, of which more than 80% are Endemism to Madagascar....
 and New Zealand
New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses , and numerous Islands of New Zealand, most notably Stewart Island/Rakiura and the Chatham Islands....
 are amphidromic points in the sense that the tide goes around them (counterclockwise in both cases) in about 12 and a half hours, but the amplitude of the tides on their coasts is in some places large.

M2 is the largest (semidiurnal) tidal constituent.






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Encyclopedia


An amphidromic point is a point within a tidal system where the tidal range
Tidal range

The tidal range is the vertical difference between the highest high tide and the lowest low tide. In other words, it is the difference in height between high and low tides....
 is almost zero.

Amphidromic points occur because of the coriolis effect
Coriolis effect

In physics, the Coriolis effect is an apparent deflection of moving objects when they are viewed from a rotating reference frame.Newton's laws of motion govern the motion of an object in an inertial frame of reference....
 and interference
Interference

In physics, interference is the addition of two or more waves that result in a new wave pattern.Interference usually refers to the interaction of waves which are correlated or Coherence with each other, either because they come from the same source or because they have the same or nearly the same frequency....
 within oceanic basin
Oceanic basin

Hydrologically, an oceanic basin may be anywhere on Earth that is covered by seawater, but geologically ocean basins are large Basin that are below sea level....
s, sea
SEA

See also: Sea and seasThe three-letter acronym SEA may refer to:People/organizations/businesses*Scientists and Engineers for America, a pro-science political advocacy group....
s and bay
Headlands and bays

Headlands and bays are two related features of the coastal environment....
s creating a wave pattern — called an amphidromic system — which rotates around the amphidromic point. At the amphidromic point, there is almost no vertical movement. There can be tidal currents as the water levels on either side of the amphidromic point are not the same.

Based on the accompanying figure, the set of clockwise amphidromic points includes:
  • north of the Seychelles
    Seychelles

    Seychelles , officially the Republic of Seychelles , is an archipelago Country of 115 islands in the Indian Ocean, some east of mainland Africa, northeast of the island of Madagascar....
  • near Enderby Land
    Enderby Land

    Enderby Land is a projecting land mass of Antarctica, extending from Shinnan Glacier at about 44? 38' E to William Scoresby Bay at 59? 34' E. It was discovered in February 1831 by John Biscoe in the Tula, and named after the Enderby Brothers of London, owners of the Tula, who encouraged their captains to combine exploration with sealing....
  • off Perth
    Perth, Western Australia

    Perth is the List of Australian capital cities and largest city of the Australian States and territories of Australia of Western Australia. With a population of 1,554,769 , Perth ranks fourth amongst the nation's cities, with a growth rate consistently above the national average....
  • east of New Guinea
    New Guinea

    New Guinea, located just north of Australia, is the List of islands by area, having become separated from the Australian mainland when the area now known as the Torres Strait flooded after the last glacial period....
  • south of Easter Island
    Easter Island

    Easter Island is a Polynesian island in the southeastern Pacific Ocean, at the southeastern most point of the Polynesian triangle. The island is a special territory of Chile....
  • west of the Galapagos Islands
    Galápagos Islands

    Gal?pagos Islands are an archipelago of Island#Volcanic islands distributed around the equator in the Pacific Ocean, 972 km west of continental Ecuador....
  • north of Queen Maud Land
    Queen Maud Land

    Queen Maud Land is an English translation of Dronning Maud Land, the official name in use by Norwegian authorities and British Antarctic Survey on the part of Antarctica claimed by Norway as a dependent territory, on 14 January 1939....


Anti-clockwise amphidromic points include:
  • near Sri Lanka
    Sri Lanka

    Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is an island country in South Asia, located about off the southern coast of India....
  • north of New Guinea
    New Guinea

    New Guinea, located just north of Australia, is the List of islands by area, having become separated from the Australian mainland when the area now known as the Torres Strait flooded after the last glacial period....
  • at Tahiti
    Tahiti

    O Tahiti is the largest island in the Windward Islands group of French Polynesia, located in the archipelago of Society Islands in the southern Pacific Ocean....
  • between Mexico
    Mexico

    The United Mexican States , commonly known as Mexico , is a federalism constitutionalism republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of Mexico....
     and Hawaii
    Hawaii

    File:Pahoehoe and Aa flows at Hawaii.jpgThe State of Hawaii is a U.S. state in the United States, located on an archipelago in the central Pacific Ocean southwest of the continental United States, southeast of Japan, and northeast of Australia....
  • near the Leeward Islands
    Leeward Islands

    The Leeward Islands are the northern islands of the Lesser Antilles chain of islands, part of the West Indies. They are situated where the Caribbean Sea meets the western Atlantic Ocean....
  • east of Newfoundland
  • midway between Rio de Janeiro
    Rio de Janeiro

    Rio de Janeiro , is the second largest city of Brazil and South America, behind S?o Paulo, and the third largest metropolitan area in South America, behind S?o Paulo and Buenos Aires....
     and Angola
    Angola

    Angola, officially the Republic of Angola , is a country in south-central Africa bordering Namibia to the south, Democratic Republic of the Congo to the north, and Zambia to the east, and with a west coast along the Atlantic Ocean....
  • east of Iceland
    Iceland

    Iceland, officially the Republic of Iceland , is an island country located in the North Atlantic Ocean between mainland Europe and Greenland....


The islands of Madagascar
Madagascar

Madagascar, or Republic of Madagascar , is an island nation in the Indian Ocean off the southeastern coast of Africa. The main island, also called Madagascar, is the List of islands by area, and is home to 5% of the world's plant and animal species, of which more than 80% are Endemism to Madagascar....
 and New Zealand
New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses , and numerous Islands of New Zealand, most notably Stewart Island/Rakiura and the Chatham Islands....
 are amphidromic points in the sense that the tide goes around them (counterclockwise in both cases) in about 12 and a half hours, but the amplitude of the tides on their coasts is in some places large.

M2 is the largest (semidiurnal) tidal constituent. The amplitude is half of the full tidal range. Cotidal points means they reach high tide at the same time and low tide at the same time. In the accompanying figure, the low tide lags or leads by 1 hr 2 min from its neighboring lines. Where the lines meet are amphidromes
Amphidromic point

An amphidromic point is a point within a tidal system where the tidal range is almost zero.Amphidromic points occur because of the coriolis effect and interference within oceanic basins, seas and Headlands and bayss creating a wave pattern ? called an amphidromic system ? which rotates around the amphidromic point....
 and the tide rotates around them; for example: along the Chilean coast, and from southern Mexico to Peru the tide propagates southward, while from Baja California to Alaska the tide propagates northward.