The World Ocean: parts, floor and water

The continuous water shell of the globe is called the World Ocean; the term was introduced by the Russian scientist Y. Shokalsky in 1917. It covers 361 million km²: water covers 61 % of the surface in the Northern Hemisphere and 81 % in the Southern. Exploration of the ocean quickened in the Age of Great Geographic Discoveries (late 15th – early 17th century): C. Columbus (1492), V. da Gama (1498), F. Magellan (the first voyage around the world, 1519–1522), F. Drake, A. Tasman and others sailed. Later J. Cook, Kruzenshtern, Bellingshausen and Lazarev, and the “Challenger” expedition (which founded oceanography) carried out research. In 1960 the Swiss Jacques Piccard and the American Don Walsh descended to the bottom of the Mariana Trench in a bathyscaphe (the textbook names J. Piccard). Parts of the ocean: a sea is a part of the ocean separated by land or islands; a gulf (bay) is a part cutting into the land; a strait is a narrow water link between two water bodies (Drake, Mozambique, Gibraltar, English Channel). B. Varenius divided the World Ocean into five oceans in 1650, later it was four; the Southern Ocean was delimited in 2000 by the International Hydrographic Organization and in 2021 National Geographic officially recognised it as the fifth ocean.