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The Río de la Plata ((:ˈriːo ðe la ˈplata), ''River of Silver'') — rendered River Plate in British English and the Commonwealth and La Plata River (occasionally Plata River) in other English-speaking countries — is the estuary formed by the confluence of the Uruguay and the Paraná rivers. It forms a funnel-shaped indentation on the southeastern coastline of South America, about long. The Río de la Plata widens from about at the inner part to about at its mouth. It forms part of the border between Argentina and Uruguay, with the major ports and capital cities of Buenos Aires and Montevideo on its western and northern shores, respectively. The coasts of the Río de la Plata are the most densely populated areas of Argentina and Uruguay.〔 The Battle of the River Plate took place in its waters in December 1939, making it the first naval battle in the Second World War, and the first one of Battle of the Atlantic. ==Geography== Some geographers consider the Río de la Plata a gulf or marginal sea of the Atlantic Ocean, while others consider it a river.〔(【引用サイトリンク】publisher= Encyclopædia Britannica )〕 For those who regard it to be a river, it is the widest in the world, with a maximum width of about and a total surface area of about .〔 The Río de la Plata behaves as an estuary in which freshwater and seawater mix. Its freshwater comes from the Paraná River, one of the world's longest and the Río's main tributary, as well as from the Uruguay River and other smaller streams. Currents in the Río de la Plata are controlled by tides reaching to its source and beyond, into the Uruguay and Paraná rivers.〔 Both rivers are tidally influenced for about .〔 The tidal ranges in the Río de la Plata are small, but its large width allows for a tidal prism important enough to dominate the flow regime despite the huge discharge received by the tributary rivers. The rivers' discharge is strong enough to prevent salt water from penetrating the inner Río de la Plata. A submerged shoal, the Barra del Indio, acts as a barrier, dividing the Río de la Plata into an inner freshwater riverine area and an outer brackish estuarine area. The shoal is located approximately between Montevideo and Punta Piedras (the northwest end of Samborombón Bay). It is the freshwater of the inner area that causes many to describe the Río de la Plata as a river.〔 The depth of the inner fluvial zone is between about . It is about long and up to wide. The depth of the outer estuary zone increases from .〔 The Río de la Plata is a salt wedge estuary. Saltwater, being denser than freshwater, penetrates into the estuary in a layer below the freshwater, which floats on the surface. Salinity fronts, or haloclines, form at the bottom and on the surface, where fresh and brackish waters meet. The salinity fronts are also pycnoclines due to the water density discontinuities. They play an important role in the reproductive processes of fish species.〔 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「Río de la Plata」の詳細全文を読む スポンサード リンク
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