Amazon River

A satellite image of the mouth of the Amazon River, looking south

This article is about the river. For other uses, see Amazon (disambiguation)

The Amazon River or River Amazon (Template:Lang-pt; Spanish: Río Amazonas) of South America is the largest river in the world by volume, with a total river flow greater than the next top ten largest rivers flowing into the ocean combined.

The Amazon River accounts for approximately 1/5 of the world's total river flow, and it has the largest drainage basin in the world. There is an ongoing dispute regarding its length, and along with the Nile it is one of the contenders for the position as the longest river in the world. Because of its vast dimensions, it is sometimes called The River Sea (o rio-mar in Portuguese), and at no point is it crossed by bridges. In 1500, Vicente Yañez Pinzón was the first European to sail into the river. Pinzón called the river flow "Río Santa María de la Mar Dulce", later shortened to "Mar Dulce" (sweet sea).

Drainage basin

The Amazon basin, the largest drainage basin in the world, covers an area of some 6,915,000 square kilometres (2,670,000 sq mi), or some 40 percent of South America. It gathers its waters from 5 degrees north latitude to 20 degrees south latitude. Its most remote sources are found on the inter-Andean plateau, just a short distance from the Pacific Ocean.

The area covered by the water of the River and its tributaries more than triples over the course of a year. In an average dry season 110,000 square kilometres (42,000 sq mi) of land are water-covered, while in the wet season the flooded area of the Amazon Basin rises to 350,000 square kilometres (135,000 sq mi). At its widest point the Amazon River can be 11 kilometres (7 mi) wide during the dry season, but during the rainy season when the Amazon floods the surrounding plains it can be up to 45 kilometres (28 mi) wide.

The quantity of fresh water released by the Amazon to the Atlantic Ocean is enormous: up to 300,000 m³ per second in the rainy season. The Amazon is responsible for a fifth of the total volume of fresh water entering the oceans worldwide. Offshore of the mouth of the Amazon, potable water can be drawn from the ocean while still out of sight of the coastline, and the salinity of the ocean is notably lower a hundred miles out to sea.

Origins of the river

The Amazon originates from the Apacheta cliff in Arequipa at the Nevado Mismi, with a sole sign of a wooden cross.

Source of the Amazon

Confluence of the Rio Negro and the Amazon near Manaus, Brazil

Today, the Upper Amazon has a series of major river systems in Peru (many of which are alike in Ecuador) that flow North and South into the Marañón and Amazon River. Among others, these include the following rivers: Morona, Pastaza, Nucuray, Urituyacu, Chambira, Tigre, Nanay, Napo, Huallaga, and Ucayali. The same as in the snow-crested Andes high above Lake Lauricocha in central Peru, the headstream of the Marañón River - which for many years had been seen as the origin of the Amazon - rises in the glaciers in what is known as the Nevado de Yarupa. Rushing through waterfalls and gorges in an area of the high jungle called the pongos, the Marañón River flows about 1,000 miles (1,600 km) from west-central to northeast Peru before it combines with the Ucayali River, just below the provincial town of Nauta, to form the mighty Amazon River.

The most distant source of the Amazon was firmly established in 1996, 2001 and 2007 as a glacial stream on a snowcapped 5,597 m (18,363 ft) peak called Nevado Mismi in the Peruvian Andes, roughly 160 km (100 mi) west of Lake Titicaca and 700 km (430 mi) southeast of Lima. The waters from Nevado Mismi flow into the Quebradas Carhuasanta and Apacheta, which flow into the Río Apurímac which is a tributary of the Ucayali which later joins the Marañón to form the Amazon proper.

Formally, though, the union of the Ucayali and the Marañón form the Río Amazonas, which changes its name to Solimões on the triple frontier between Peru, Colombia and Brazil, and later changes its name back to the Amazon only after it meets the Rio Negro near Manaus. After the confluence of Río Apurímac and Ucayali, the river leaves Andean terrain and is instead surrounded by flood plain. From this point to the Marañón, some 1,600 km (990 mi), the forested banks are just out of water, and are inundated long before the river attains its maximum flood-line. The low river banks are interrupted by only a few hills, and the river enters the enormous Amazon Rainforest.

The river systems and flood plains in Brazil, Peru, Ecuador, Colombia and Venezuela whose waters drain into the Solimões and its tributaries are called the "Upper Amazon".

Flooding

A NASA satellite image of a flooded portion of the river.

The average depth of the river in the height of the rainy season is 40 m (131 ft) and the average width can be nearly 40 km (25 mi). It starts to rise in November, and increases in volume until June, then falls until the end of October. The rise of the Negro branch is not synchronous; the rainy season does not commence in its valley until February or March. By June it is full, and then it begins to fall with the Amazon. The Madeira rises and falls two months earlier than the Amazon.

The main river (which is between approximately one and six miles (10 km) wide) is navigable for large ocean steamers to Manaus, 1,500 kilometres (930 mi) upriver from the mouth. Smaller ocean vessels of 3,000 tons and 5.5 metres (18 ft) draft can reach as far as Iquitos, Peru, 3,600 kilometres (2,240 mi) from the sea. Smaller riverboats can reach 780 kilometer (485 mi) higher as far as Achual Point. Beyond that, small boats frequently ascend to the Pongo de Manseriche, just above Achual Point.

Towards the sea

The breadth of the Amazon in some places is as much as 6 km (4 mi) to 10 km (6 mi) from one bank to the other. At some points, for long distances, the river divides into two main streams with inland and lateral channels, all connected by a complicated system of natural canals, cutting the low, flat igapo lands, which are never more than 5 m (16 ft) above low river, into many islands.

From the village of Canaria at the great bend of the Amazon to the Negro, only very low land is found, resembling that at the mouth of the river. Vast areas of land in this region are submerged at high water, above which only the upper part of the trees of the sombre forests appear. Near the mouth of the Rio Negro to Serpa, nearly opposite the river Madeira, the banks of the Amazon are low, until approaching Manaus, they rise to become rolling hills. At Óbidos, a bluff 17 m (56 ft) above the river is backed by low hills. The lower Amazon seems to have once been a gulf of the Atlantic Ocean, the waters of which washed the cliffs near Óbidos.

Only about 10% of the water discharged by the Amazon enters the mighty stream downstream of Óbidos, very little of which is from the northern slope of the valley. The drainage area of the Amazon basin above Óbidos city is about 5 million km² (2 million mile²), and, below, only about 1 million km² (400,000 mile²), or around 20%, exclusive of the 1.4 million km² (600,000 mile²) of the Tocantins basin.

In the lower reaches of the river, the north bank consists of a series of steep, table-topped hills extending for about 240 km (149 mi) from opposite the mouth of the Xingu as far as Monte Alegre. These hills are cut down to a kind of terrace which lies between them and the river.

Monte Alegre reaches an altitude of several hundred feet. On the south bank, above the Xingu, an almost-unbroken line of low bluffs bordering the flood-plain extends nearly to Santarem, in a series of gentle curves before they bend to the south-west, and, abutting upon the lower Tapajos, merge into the bluffs which form the terrace margin of the Tapajos river valley.

Mouth of the river

Mouth of the Amazon River

The Amazon estuary is some 330 kilometres (207 mi) wide:

The width of the mouth of the river is usually measured from Cabo do Norte to Punto Patijoca. But this includes the ocean outlet, 60 km (40 mi) wide, of the Para river, which should be deducted, as this stream is only the lower reach of the Tocantins. It also includes the ocean frontage of Marajó, an island lying in the mouth of the Amazon. This means that the Amazon is wider at its mouth than the entire length of the Thames in England.

Tidal bore

Following the coast, a little to the north of Cabo do Norte, and for 160 kilometres (99 mi) along its Guiana margin up the Amazon, is a belt of half-submerged islands and shallow sandbanks. Here the tidal phenomenon called the bore, or pororoca, occurs, where the depths are not over 7 metres (23 ft). The tidal bore starts with a roar, constantly increasing, and advances at the rate of from 15 km/h (9 mph) to 25 km/h (16 mph), with a breaking wall of water from 1.5 m (5 ft) to 4 m (13 ft) high. The bore is the reason the Amazon does not have a delta; the ocean rapidly carries away the vast volume of silt carried by the Amazon, making it impossible for a delta to grow. It also has a very large tide sometimes reaching 20 feet (6 m) and has become a popular spot for river surfing.[1]

Amazon River at dawn

Wildlife

More than one third of all species in the world live in the Amazon Rainforest, a giant tropical forest and river basin with an area that stretches more than 2.1 million square miles and is among the richest tropical forests in the world. Amazon river has over 3,000 recognized species of fish and that number is still growing. Some estimates go as high as 5,000.

The waters of the Amazon support a diverse range of wildlife. Along with the Orinoco, the river is one of the main habitats of the Boto, also known as the Amazon River Dolphin. The largest species of river dolphin, it can grow to lengths of up to 2.6 metres (9 ft).

Also present in large numbers are the notorious Piranha, carnivorous fish which congregate in large schools, and may attack livestock and even humans. Although many experts believe their reputation for ferocity is unwarranted, a school of piranha was apparently responsible for the deaths of up to 300 people when their boat capsized near Óbidos in 1981. However, only a few species attack humans, and many are solely fish-eaters, and do not school.

The Bull Shark has been reported 2,220 miles (4000 km) up the Amazon River at Iquitos in Peru. The Arapaima, or pirarucu (Arapaima gigas) is a South American tropical freshwater fish. It is one of the largest freshwater fish in the world, reportedly with a maximum length in excess of 3 m (9.8 ft) and weight up to 200 kg (440 lb.).

The Anaconda snake is found in shallow waters in the Amazon basin. One of the world's largest species of snake, the Anaconda spends most of its time in the water, with just its nostrils above the surface. Anacondas have been known to occasionally attack fishermen .

The river supports thousands of species of fish, as well as crabs, algae, and turtles.

The Colonial Encounter and Amazonia

During what many archaeologists call the formative period, Amazonian societies were deeply involved in the emergence of South America's highland agrarian systems, and possibly contributed directly to the social and religious fabric constitutive of the Andean civilizational orders[2].

For 350 years after the European discovery of the mighty Amazon by Vicente Yáñez Pinzón, the Portuguese portion of the basin remained an untended former food gathering and planned agricultural landscape occupied by the Indigenous peoples who survived the arrival of European diseases. There is ample evidence for complex large-scale, pre-Columbian social formations, including chiefdoms, in many areas of Amazonia (particularly the inter-fluvial regions) and even large towns and cities. For instance the pre-Colombian culture on the island of Marajo may have developed Social stratification and supported a population of 100,000 people. The Native Americans of the Amazon rain forest may have used Terra preta to make the land suitable for the large scale agriculture needed to support large populations and complex social formations such as Cheifdoms.

In what is currently Brazil, Ecuador, Bolivia, Colombia, Peru, and Venezuela a number of colonial and religious settlements were established along the banks of primary rivers and tributaries for the purpose of trade, slaving and evangelization among the putatively savage indigenous peoples of the vast rain forest.

The total population of the Brazilian portion of the Amazon basin in 1850 was perhaps 300,000, of whom about two-thirds comprised by Europeans and slaves, the slaves amounting to about 25,000. In Brazil, the principal commercial city, Para (now Belém), had from 10,000 to 12,000 inhabitants, including slaves. The town of Manáos, now Manaus, at the mouth of the Rio Negro, had from 1,000 to 1,500 population. All the remaining villages, as far up as Tabatinga, on the Brazilian frontier of Peru, were relatively small.

On September 6 1850, the emperor, Dom Pedro II, sanctioned a law authorizing steam navigation on the Amazon, and gave Barão de Mauá (Irineu Evangilista de Sousa) the task of putting it into effect. He organized the "Compania de Navigacao e Commercio do Amazonas" at Rio de Janeiro in 1852; and in the following year it commenced operations with three small steamers, the Monarch, the Marajó and Rio Negro.

At first, navigation was principally confined to the main river; and even in 1857 a modification of the government contract only obliged the company to a monthly service between Pará and Manaus, with steamers of 200 tons cargo capacity, a second line to make six round voyages a year between Manaus and Tabatinga, and a third, two trips a month between Para and Cameta. This was the first step in opening up the vast interior.

The success of the venture called attention to the opportunities for economic exploitation of the Amazon, and a second company soon opened commerce on the Madeira, Purus and Negro; a third established a line between Pará and Manaus; and a fourth found it profitable to navigate some of the smaller streams. In that same period, the Amazonas Company was increasing its fleet. Meanwhile, private individuals were building and running small steam craft of their own on the main river as well as on many of its tributaries.

On July 31 1867 the government of Brazil, constantly pressed by the maritime powers and by the countries encircling the upper Amazon basin, especially Peru, decreed the opening of the Amazon to all flags; but limited this to certain defined points: Tabatinga—on the Amazon; Cameta—on the Tocantins; Santarem—on the Tapajos; Borba—on the Madeira and Manáos—on the Rio Negro. The Brazilian decree took effect on 7 September 1867.

Thanks in part to the mercantile development associated with steam boat navigation, coupled with the internationally driven demand for natural rubber (1880-1920), Manáos (now Manaus), Para (Brazil), and Iquitos, Peru became thriving, cosmopolitan centers of commerce and spectacular—albeit illusory—modern "urban growth". This was particularly the case for Iquitos during its late 19th and early 20th century Rubber Bonanza zenith when this dynamic boom-town was known abroad as the St. Louis of the Amazon.

The first direct foreign trade with Manáos was commenced around 1874. Local trade along the river was carried on by the English successors to the Amazonas Company—the Amazon Steam Navigation Company—as well as numerous small steamboats, belonging to companies and firms engaged in the rubber trade, navigating the Negro, Madeira, Purfis and many other tributaries, such as the Marañón to ports as distant as Nauta, Peru.

By the turn of the 20th century, the principal exports of the Amazon Basin were india-rubber, cacao, Brazil nuts and a few other products of minor importance, such as pelts and exotic forest produce (resins, barks, woven hammocks, prized bird feathers, live animals, etc.) and extracted goods (lumber, gold, etc.).

20th century concerns

Four centuries after the European discovery of the Amazon river, the total cultivated area in its basin was probably less than 25 square miles (65 km²), excluding the limited and crudely cultivated areas among the mountains at its extreme headwaters. This situation changed dramatically during the 20th century.

Manaus, the largest city on the Amazon, as seen from a NASA satellite image, surrounded by the muddy Amazon River and the dark Rio Negro.

Wary of foreign exploitation of the nation's resources, Brazilian governments in the 1940s set out to develop the interior, away from the seaboard where foreigners owned large tracts of land. The original architect of this expansion was President Getúlio Vargas, the demand for rubber from the Allied forces in World War II providing funding for the drive.

The construction of the new capital Brasilia in the interior in 1960 also contributed to the opening up of the Amazon basin. A large scale colonization program saw families from north-eastern Brazil relocated to the forests, encouraged by promises of cheap land. Many settlements grew along the road from Brasilia to Belém, but rainforest soil proved difficult to cultivate.

Still, long-term development plans continued. Roads were cut through the forests, and in 1970, the work on Trans-Amazon highway network began. The network's three pioneering highways were completed within ten years, connecting all the major cities of the Brazilian Amazon interior.

Dispute regarding length

While debate as to whether the Amazon or the Nile is the world's longest river has gone on for many years, the historic consensus of geographic authorities has been to regard the Amazon as the second longest river in the world, with the Nile being the longest. However, the Amazon has been measured by different geographers as being anywhere between 6,259 kilometres (3,889 mi) and 6,800 kilometres (4,225 mi) long. The Nile River in Africa is reported to be anywhere from 5,499 kilometres (3,417 mi) to 6,690 kilometres (4,157 mi). The differences in these measurements often result from the use of different definitions.

A recent study by Brazilian scientists claims that the Amazon is actually longer than the Nile. Using Nevado Mismi, which was labeled by the National Geographic Society as the Amazon's source back in 2001, these scientists have made new calculations of the Amazon's length. They now estimate that the Amazon is 65 miles (105 km) longer than the Nile, and Guido Gelli, director of science at the Brazilian Institute of Geography and Statistics (IBGE), told the Brazilian TV network Globo in June 2007 that it could be considered as a fact that the Amazon was the longest river in the world. However, other geographers have had access to the same data since 2001, and a consensus has yet to emerge to support the claims of these Brazilian scientists.

Regardless of the actual length, the Amazon carries by far the greatest volume of any of Earth's rivers.

Major tributaries

The Amazon has over 1,000 tributaries in total, 17 of which are over 1,000 kilometers. Some of the more notable:

Branco Casiquiare canal Huallaga Putumayo (or Içá River) Javary Jurua Madeira Marañón Morona Nanay Napo Negro

Pastaza Purus Tambo Tapajós Tigre Tocantins Trombetas Ucayali Xingu Yapura

Longest rivers in the Amazon system

1. 6,387 km (3,969 mi) - Amazon, South America
2. 3,379 km (2,100 mi) - Purus, Peru / Brazil, (2,948 km) (3,210 km)
3. 3,239 km (2,013 mi) - Madeira, Bolivia / Brazil
4. 2,820 km (1,752 mi) - Yapura, Colombia / Brazil
5. 2,750 km (1,709 mi) - Tocantins, Brazil, (2,416 km) (2,640 km)
6. 2,575 km (1,600 mi) - Araguaia, Brazil (tributary of Tocantins)
7. 2,410 km (1,498 mi) - Juruá, Peru / Brazil
8. 2,250 km (1,398 mi) - Negro, South America
9. 2,100 km (1,305 mi) - Xingu, Brazil
10. 1,900 km (1,181 mi) - Tapajós, Brazil
11. 1,749 km (1,087 mi) - Guaporé, Brazil / Bolivia (tributary of Madeira)
12. 1,575 km (979 mi) - Içá (Putumayo), South America
13. 1,415 km (879 mi) - Marañón, Peru
14. 1,300 km (808 mi) - Iriri, Brazil (tributary of Xingu)
15. 1,240 km (771 mi) - Juruena, Brazil (tributary of Tapajós)
16. 1,200 km (746 mi) - Tapajós, Brazil
17. 1,130 km (702 mi) - Madre de Dios, Peru / Bolivia (tributary of Madeira)
18. 1,100 km (684 mi) - Huallaga, Peru (tributary of Marañón)

See also

• Orders of magnitude (length)

References

• This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press. {{cite encyclopedia}}: Missing or empty |title= (help)

External links

• Amazon dries up Youtube (July 31, 2006)
• Bibliography on Water Resources and International Law See Amazon River. Peace Palace Library
• Amazon River and Amazon Rainforest virtual tour
• Information on the Amazon from Extreme Science
• Fundación Gaia Amazonas Template:En icon Template:Es icon
• Pictures of the Amazon River
• Amazon River and Amazon rainforest information
• An Amazon River web site
• Information and a map of the Amazon's watershed
• Expedition to the source 1996
• Expedition to the source 2001
• Amazon river 'longer than Nile' (BBC News)
• Territorial-Environmental Information System of Colombian Amazon SIAT-AC