GeographyThe Río de la Plata begins at the of the Uruguay and Paraná rivers at Punta Gorda and flows eastward into the South Atlantic Ocean. No clear physical boundary marks the river's eastern end; the International Hydrographic Organization defines the eastern boundary of the Río de la Plata as "a line joining Punta del Este, and Cape San Antonio, Argentina, Cabo San Antonio, ". Though it is generally spoken of as a river, the Río de la Plata is considered by some geographers to be a large bay or marginal sea of the Atlantic Ocean. For those who regard it as a river, it is the widest in the world, with a maximum width of about and a total surface area of about .
Islands and shoalsThe upper river contains several islands, including Oyarvide Island and the Solís Islands in Argentine waters and Juncal Island, Islote el Matón, Martín García Island and Timoteo Domínguez Island in Uruguayan waters. Because of deposition of sediments from the heavy stream load carried down from the river's tributaries, the islands in the Río de la Plata generally grow over time. A submerged shoal, the Barra del Indio, divides the Río de la Plata into an inner freshwater riverine portion and an outer brackish estuarine portion. The shoal is located approximately between and Punta Piedras (the northwest end of Samborombón Bay). The inner fluvial zone is about long and up to wide, with a depth which varies from about ; the depth of the outer estuary zone increases from . The river's discharge is strong enough to prevent saltwater from penetrating to the inner portion.
HydrologyThe Río de la Plata behaves as an estuary in which freshwater and seawater mix. The freshwater comes principally from the (one of the world's longest rivers and La Plata's main tributary) as well as from the Uruguay River and other smaller streams. Currents in the Río de la Plata are dominated by tides reaching to its sources 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 great width allows for a tidal prism important enough to dominate the flow regime despite the huge discharge received from the tributary rivers. The river is a Estuary#Salt wedge, salt wedge estuary in which saltwater, being more dense 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.
Drainage basinThe Río de la Plata's drainage basin (sometimes called the Platine basin or Platine region) is the hydrographical area that drains to the Río de la Plata. It includes areas of southeastern Bolivia, southern and central Brazil, the entire country of Paraguay, most of , and northern . Making up about one fourth of the continent's surface, it is the second largest drainage basin in South America (after the Amazon basin) and one of the largest in the world.
TributariesThe main rivers of the La Plata basin are the , the Paraguay River (the Paraná's main tributary), and the Uruguay River. The Paraná River's main tributaries include the Paranaíba River, Rio Grande (Paraná River), Grande River, Tietê River, Paranapanema River, Iguazu River, Paraguay River, and the Salado River (Argentina), Salado River, after which it ends in the large Paraná Delta. The Paraguay River flows through the Pantanal wetland, after which its main tributaries include the Pilcomayo River and the Bermejo River, before it ends in the Paraná. The Uruguay's main tributaries include the Pelotas River, Canoas River (Santa Catarina), Canoas River, Ibicuí River, and the Río Negro (Uruguay), Río Negro. Another significant tributary to the Río de la Plata is the Salado del Sur River.
European explorationThe Río de la Plata was first explored by the Portuguese in 1512–13. The Spanish first explored it in 1516, when the navigator Juan Díaz de Solís traversed it during his search for a passage between the Atlantic and the Pacific Oceans, calling it the Mar Dulce, or "freshwater sea." The Portuguese navigator Ferdinand Magellan briefly explored the estuary in 1520 before his expedition continued its circumnavigation, and in 1521 Cristóvão Jacques also explored the Plate River estuary and ascended the Parana River for the first time, entering it for about 23 leagues (around 140 km) to near the present city of Rosario, Santa Fe, Rosario. The area was also visited by Francis Drake's fleet in early 1578, in the early stages of his circumnavigation. Explorer Sebastian Cabot (explorer), Sebastian Cabot made a detailed study of the river and its tributaries and gave it its modern name. He explored the Paraná and Uruguay rivers between 1526 and 1529, ascending the Paraná as far as the present-day city of Asunción, and also explored up the Paraguay River. Cabot acquired silver trinkets trading with the Guarani people, Guaraní near today's Asunción, and these objects (together with legends of a "Sierra de la Plata" in the South American interior brought back by earlier explorers) inspired him to rename the river "Río de la Plata" ("River of Silver"). The first European colony was the city of Buenos Aires, founded by Pedro de Mendoza on 2 February 1536. This settlement, however, was quickly abandoned; the failure to establish a settlement on the estuary led to explorations upriver and the founding of Asunción in 1537. Buenos Aires was subsequently refounded by Juan de Garay on 11 June 1580.
Colonial periodDuring the colonial era, the Río de la Plata was made the center of the Governorate of the Río de la Plata. The Río de la Plata region, particularly , was a significant site of trade throughout the 17th century. The Crown initially intended Buenos Aires to be a military establishment for the protection of the Cerro Rico, Potosí mines, but it soon became evident that a settlement large enough to provide military defense would attract trade. The primary export was silver from the mines of Potosí, and imports generally included European luxury goods, slaves, and sugar. This trade occurred outside of the fleet system authorized by the Spanish Crown, and therefore was generally considered "illicit." However, under the monarchy of the Habsburg Spain, Spanish Habsburgs, the line between licit and illicit trade was quite blurry. Crown officials and military outposts in Buenos Aires often relied upon profits from illicit trade to support their administrative structures. Under the Bourbon Spain, Bourbon monarchy, the governorate was elevated to the Viceroyalty of the Río de la Plata in 1776. This occurred as a result of the Bourbon Reforms, which attempted to restore the decaying wealth of the Spanish Crown. The reforms elevated the status of trade along the Río de la Plata and expanded what constituted "legal" trade so that the Crown could tax trade what had previously been "contraband." However, the plan did not go as intended. Although trade along the Río de la Plata flourished, very little silver was actually remitted to the Crown. Then, Spanish war with Britain and the simultaneous eruption of revolts in the mining regions of Peru led to a shortage of silver, putting strain on the merchant class of Buenos Aires. This caused a schism between merchants who wanted to try to continue reviving the Spanish Empire through silver trade and those who wanted to move on from silver and prioritize agricultural exports, ultimately tearing at the fabric of the Río de la Plata region's relationship with the Spanish Empire. In 1806 and 1807 the river was the scene of an important British invasions of the Río de la Plata, British invasion that aimed to occupy the area and was defeated by the local garrison and population.
Revolutionary periodConflict in the region intensified after the Spanish American wars of independence, independence of the former Spanish and Independence of Brazil, Portuguese colonies in the first quarter of the 19th century. Interests in the territories and the navigation rights over the La Plata Basin, Platine region played a major role in many armed conflicts throughout the century, including the Argentine Civil War, Argentine civil wars, the Cisplatine War, Cisplatine and Platine War, Platine wars, and the Paraguayan War. The river was blockaded by France and Britain in French blockade of the Río de la Plata, 1838–1840 and Anglo-French blockade of the Río de la Plata, 1845–1850.
Battle of Juncal (1827)During the Cisplatine War, the Battle of Juncal (named after Juncal Island) took place in the waters of the Río de la Plata from 8–9 February 1827 between squadrons of the newly independent United Provinces of the River Plate and the Brazilian Empire. The Argentines scored a decisive victory, capturing or destroying fifteen Brazilian vessels and losing none.
Battle of the River Plate (1939)In the first naval battle of the World War II, Second World War the German pocket battleship ''German pocket battleship Admiral Graf Spee, Admiral Graf Spee'' was engaged by the Royal Navy (RN) cruisers and , and the Royal New Zealand Navy cruiser , off the estuary of the River Plate in December 1939. The German ship retired up the estuary with a crippled fuel system and put into port at Montevideo. A few days later, rather than fight when believing himself outgunned, her captain scuttled her in the estuary. This engagement was part of the early Battle of the Atlantic#Early skirmishes (September 1939 – May 1940), Battle of the Atlantic.
English namesThe historical English name "River Plate" uses an obsolete sense of the word "plate", which was used extensively as a term for "silver" or "gold" from the 12th century onwards, especially in Early Modern English. The estuary has been known as the ''River Plate'' or ''Plate River'' in English since at least the time of Francis Drake. This English version of the name served as an inspiration for one of Argentina's most important association football, football clubs, Club Atlético River Plate. A more literal translation of the name is "Silver River", though this is virtually never used in practice.
FaunaThe Río de la Plata is a habitat for the loggerhead sea turtle, green sea turtle, leatherback sea turtle, the rare La Plata dolphin, and many species of fish.
See also*Rioplatense Spanish *Argentina–Uruguay relations *1973 Boundary Treaty between Uruguay and Argentina *The Fontana dei Quattro Fiumi, in Rome's Piazza Navona, contains a figure representing the River Plate. *1888 Río de la Plata earthquake
Bibliography* * * * *Real, Walter. ''España en el Río de la Plata: Descubrimiento y Poblamientos (1516–1588)''. Montevideo: Club Español. 2001. . *