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The Romanche Trench, also called the ''Romanche Furrow'' or ''Romanche Gap'', is the third deepest of the major trenches of the Atlantic Ocean, after the Puerto Rico Trench and the South Sandwich Trench. It bisects the Mid-Atlantic Ridge (MAR) just north of the equator at the narrowest part of the Atlantic between Brazil and West Africa, extending from 2°N to 2°S and from 16°W to 20°W. The trench has been formed by the actions of the Romanche Fracture Zone, a portion of which is an active transform boundary offsetting sections of the Mid-Atlantic Ridge. ==Oceanography== The trench has a depth of , is long and has an average width of and allows for a major circulation of deep ocean basin water from the west Atlantic to the east Atlantic basins. Deep water flow through the trench is from west to east with a rate of 3.6 Sverdrups (million m³/s) of water.〔 Lower North Atlantic Deep Water (LNADW) is found around below sea level and flows from the Greenland and Norwegian Seas; it brings high salinity, oxygen, and freon concentrations towards the equator. Antarctic Bottom Water (AABW) flows below the LNADW and reaches down to the seafloor. Formed around Antarctica, the AABW is cold, has low salinity, and high silicate concentration. As it flows north, it is constrained by numerous obstacles on the seafloor. In the basin on the eastern side of the MAR the Walvis Ridge blocks the northward passage. For LNADW and AABW, the Romanche and Chain Fracture Zones (just south of the equator) are the only deep passages in the MAR where interbasin exchange is possible. As AABW flows through the Romanche Fracture Zone, salinity and temperature increase significantly. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Romanche Trench」の詳細全文を読む スポンサード リンク
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