Competitive Exams: Oceanography Oceans of World

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Basics for Plate Tectonics

Atlantic Ocean

  • 1/6 of the geographical area (8,20,00,000 km sq.) and half the area of Pacific ocean;

  • It is located between North and South America in the west and between Europe and Africa in the east;

  • It is'S' shaped;

  • Its width is minimum between Liberian coast and Cape Sauroque (256)km.;

  • About 24% of Atlantic is 915 m deep.

Continental Shelf in the Atlantic Ocean

  • Width 2.24 km. more than 80 km.;

  • It is narrowest at the bay of Biscay, Cape of Good Hope and the Brazilian Shelf i.e. S to S latitude and widest near New Foundland

  • Important Continental Shelf are found at Hudson Bay, Baltic sea, North sea, Davis Strait, Denmark Strait, British Isles, Iceland, St. Helena, West Indies, Trinidad, Falkland, S. Orkneys, S. Shetland, S. Georgia, S. Sandwich, Canary island, Cape Verde, St. Pierre and Miquelone island, Madeira island.

Mid Atlantic Ridge

  • Dolphin Rise and Challenger Rise north of Equator

  • Wyville Thompson Ridge or Challenger Rise, south of equator;

  • Telegraphic Plateau between South of Greenland and Iceland;

  • New Foundland, Azores Rise, Sierra Leon, Para Rise, Unea Ridge.

  • In North Atlantic North American Basin; Puerto Rico Basin (8,000 m. deep).

  • In the South Atlantic east South American Coast; Argentina Basin; South Atlantic Ridge; Walvis Ridge; Cape Basin; Cape Town.

Indian Ocean

  • It is smaller than the Atlantic and Pacific Ocean

  • Average depth is 4,000 m.

  • Formed by the blocked mountains of Gondwana land

  • Important seas are: Mozambique Channel, Red Sea, Persian Gulf, Andaman Sea, Arabian Sea, Bay of Bengal

  • Important islands. Madagascar, Sri Lanka, Suqutra or Socotra Island, Zanzibar Island, Comoros Island, Mauritius, Reunion Island, Rodrique Island, Caragos Island, Chagos Archipelago and Diego Garcia Island, Mayotte Island, Seychelles Island, Victoria, Mahe, Addabra Island, Prince Edward Island, St. Paul, Maldives, Lakshwadeep, Andaman and Nicobar, Christmas Island, Crozet Island.


  1. Mid Oceanic Ridge: Average width is 320 km. and includes: Lakshwadweep.Chagos Ridge or Maldives ridge; It is called Chagos St. Paul Ridge between Equator and South; It is called Amsterdam St. Paul Plateau between South latitude; After it bifurcates; Western branch is called Kergulian Gaussberg Ridge: South latitude . eastern branch is called the Indian Antarctic ridge.

  2. Central Ridge: Socotra Chagos Ridge, also known as Charlesberg Ridge, emerges from the central ridge at South latitude and extends in northwesterly direction in almost accurate shape upto Garadaphool Peninsula of N.E. Africa.

  3. Seychelles Mauritius Ridge: bifurcates from the main ridge around South latitude near Mauritius island and runs upto Amirante island.

  4. Madagascar Ridge: It extends upto S latitude; at - South it is called Prince Edward Crozet Ridge.

  5. The 90 East Ridge: Extends from the Continental Shelf off the Irrawadi river mouth and runs in almost northsouth direction, parallel to east longitude and upto south, where it merges with Amsterdam St. Paul plateau.