October 17, 2021

An ocean (Ancient Greek Ωκεανός (Okeanós)) is a more or less independent ocean between the continents and can contain several (smaller) seas. There are five oceans on Earth. These are all connected to each other and together form one large mass of salt water. The oceans and seas occupy a total of 72% of the surface of the earth (~3.6 x 108 km2), of which the oceans make up the lion's share with 71%. The country (the whole of the continents and islands) makes up the rest. The oceans comprise 97% of all water on Earth. Only 5% of the oceans have been explored, according to oceanographers. In total there is about 1.3 billion cubic kilometers with an average depth of 3682 meters. In different periods in the past, all continents were connected to each other. One speaks then of supercontinents, which were surrounded by superoceans. Islands in an ocean can be divided into continental islands and oceanic islands while the latter can be further divided into volcanic islands and coral islands.

The five oceans

Since the definition of the boundaries of the Southern Ocean by the International Hydrographic Organization in 2000, five oceans are distinguished (in order of size): The Pacific Ocean, commonly known in America as the Pacific Ocean, (formerly called the South Pacific) - Bounded by (clockwise from the north) the Arctic Ocean, the western coast of the Americas, the Atlantic, Southern and Indian Ocean, the east and northeast coasts of Australia, the Indonesian archipelago and the east coast of Asia. The total area is 155,557,000 square kilometers. The main island groups in the Pacific Ocean are Polynesia, Melanesia and Micronesia. Near the island of Guam lies the deepest trough in the world; the Mariana Trench. It was discovered in 1960 and explored with the bathyscaphe Trieste to a depth of 10,916 meters. The Atlantic Ocean - Bounded by the Arctic Ocean, the west and south coasts of Europe, the north and west coasts of Africa, the Indian, Southern and Pacific Oceans, and the east coasts of South and North America. Area: 76,762,000 square kilometers. The Indian Ocean - Bounded by the south coast of Asia, the Indonesian archipelago, the west and south coasts of Australia, the Great, Southern and Atlantic Oceans, and the east coast of Africa. Area: 68,556,000 square kilometers. The Southern Ocean (also called Antarctic Ocean) - Bounded by the coast of Antarctica on one side, and the Atlantic, Indian, and Pacific Oceans on the other. The boundary with these oceans is at 60° south latitude. Area: 20,327,000 square kilometers. The Arctic Ocean (also called Arctic Ocean) - Bounded by the Atlantic Ocean, the north coast of North America, the Pacific Ocean, and the north coast of Asia and Europe. Area: 14,056,000 square kilometers. Sometimes there is also talk of seven oceans, in this case the Pacific Ocean and the Atlantic Ocean at the equator are further divided into a Northern and Southern part.

Ocean currents

The water of the oceans is in constant motion. This is visible on a large scale in the major ocean currents such as the Gulf Stream. Much of the ocean's kinetic energy, however, resides in more small-scale vortices a few tens of kilometers in size. Ultimately, all that energy comes from sunlight and the Earth's rotation. The great surface currents of the ocean are powered by trade winds and their counterparts, the westerly wind belts. Due to the Ekman spiral, the sea current does not run parallel to the wind direction. The combined effect is a collection of ring-shaped ocean currents called gyres. The Atlantic and Pacific Oceans each have a northern and a southern subtropical gyre, while the Indian Ocean has one (southern) gyre. In addition, there is a large circumpolar current r

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