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Orinoco River, Spanish Río Orinoco, significant river of south America that flows in a huge arc for some 1,700 miles (2,740 km) native its resource in the Guiana Highlands to its mouth ~ above the Atlantic Ocean. Throughout most of its course it flows through Venezuela, other than for a ar that forms part of the frontier in between Venezuela and Colombia. The surname Orinoco is obtained from Warao (Guarauno) words an interpretation “a place to paddle”—i.e., a navigable place.


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For most of its length, the Orinoco flows with impenetrable rain forest or with the substantial grassland (savanna) region of the Llanos (“Plains”), which occupies three-fifths the the Orinoco container north the the Guaviare River and west of the reduced Orinoco River and also the Guiana Highlands. The savanna was offered its name by the Spaniards in the 16th century and also long has been used as a huge cattle range. Since the 1930s this an ar has been developing into among the most industrialized locations of southern America.

Physical features

Physiography of the Orinoco

The west slopes of the Sierra Parima, which kind part that the boundary between Venezuela and Brazil, are drained through spring-fed streams that offer rise to the Orinoco River. The resource is placed in Venezuela, at the southern end of the Parima Mountains, near Mount Delgado Chalbaud, at an key of part 3,300 feet (1,000 metres). Native its headwaters the river flows west-northwest, leave the mountains to meander v the level levels of the Llanos. The volume that the river boosts as that receives numerous mountain tributaries, consisting of the Mavaca flow on the left bank and also the Manaviche, Ocamo, Padamo, and also Cunucunuma rivers top top the right.


Below the city of Esmeralda, several of the waters that the Orinoco circulation south right into the Casiquiare flow (Brazo Casiquiare; sometimes referred to as the Casiquiare Channel). This channel, a function peculiar to the Orinoco river system, is a herbal passage that flows usually south until it combines with the Guainía river to type the black River, therefore linking the Orinoco and Amazon river systems.

After the bifurcation in the Casiquiare, the Orinoco bends to the northwest and flows in an excellent meandering curves to its confluence with the Ventuari River. Over there the river turns to the west come run between high alluvial banks, its course significant by substantial sandbars. Near San Fernando de Atabapo, the Atabapo and also Guaviare rivers sign up with the Orinoco, marking the end of the top Orinoco.

Downstream from mountain Fernando de Atabapo, the flow flows northward and forms part of the border in between Venezuela and Colombia. The passes through a transitional zone, the an ar of the Rapids (Región de los Raudales), whereby the Orinoco forces its way through a collection of small passages amongst enormous granite boulders. The waters fall in a sequence of rapids, finishing with the Atures Rapids. In this region, the main tributaries space the Vichada and also Tomo rivers native the Colombian Llanos, and also the Guayapo, Sipapo, Autana, and also Cuao rivers native the Guiana Highlands.

The Atures Rapids mark the beginning of the lower Orinoco basin, in which the river provides its good bend to the east. In this section, the flow flows progressively through the lowest level that the plains and increases to about five mile in width. Follow me the bend, the receives the largest number of tributaries of its entire course, including the Meta, Arauca, and also Capanaparo rivers. The Apure flow contributes waters from plenty of Andean streams, which form a swampy maze in their lower courses.

From that junction through the Apure, the Orinoco meanders eastward over gently sloping plains. Shoals and alluvial islands room abundant; several of the archipelago are huge enough to divide the channel into narrow passages. Tributaries incorporate the Guárico, Manapire, Suatá (Zuata), Pao, and Caris rivers, which get in on the left bank, and the Cuchivero and Caura rivers, which sign up with the key stream on the right. So lot sediment is lugged by this rivers that islands often type at the mouths. The Caroní River, among the Orinoco’s largest tributaries, joins the river on that is right bank after passing v the Guri Reservoir formed by Guri (Raúl Leoni) Dam, above Ciudad Guayana (also referred to as Santo Tomé de Guayana). Furthermore upstream, ~ above the Churún river (a tributary the the Caroní), room Angel Falls, the greatest waterfall in the civilization (3,212 feet <979 metres>). Numerous lagoons, consisting of the Mamo, Amana, and also Colorada, are located on the banks of the Orinoco west the its confluence v the Caroní and east the Ciudad Bolívar.


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About 30 miles downstream of Ciudad Guayana, at the city of Barrancas, the Orinoco begins to form its great delta. The delta extend for about 275 miles follow me the Atlantic coast, native Pedernales top top the Gulf the Paria in the northwest to Barima suggest in the south east on the Boca Grande (literally, the “Great Mouth”). Scores of islands are associated by innumerable canals (caños), which form an detailed network. The key channel of the Orinoco, known in the delta as the Río Grande, flows eastward native Barrancas to discharge into the Boca Grande.

Physiography that the Orinoco Llanos

The Llanos includes nearly all of the western lower Orinoco basin, occupying part 220,000 square miles; many of the land is less than 1,000 feet over sea level. The High plains (Llanos Altos) are many conspicuous near the Andes, where they form extensive platforms in between rivers and also are some 100 come 200 feet above the sink floors. Away from the hills they are significantly fragmented, together in the dissected tableland of the main and eastern Llanos (the Sabana de Mesas) and also the hill country (serranía) south of the Meta river in Colombia. The Low levels (Llanos Bajos) are characterized by two rivers, the Apure in the north and the Meta in the south. The lowest section of the Llanos is an area the lies come the west of the reduced Orinoco valley; this area is converted yearly into one inland lake through flooding.

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In addition to the Apure and the Meta, the principal streams draining the Llanos encompass the Guaviare and also Arauca rivers. Seasonal changes between saturation and dehydration have led to advanced laterization that the soil, the process in i m sorry the basic minerals have actually been leached away or incorporated into insoluble iron and also aluminum silicates. Fine-grained soils type hardpans (cemented layers of soils), and in gravel regions, iron-cemented quartz conglomerates underlie the surface. Extreme acidity and the absence of nutrient bases, essential matter, and nitrogen make virtually all mature soils infertile.