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Amazon River

2007 Schools Wikipedia Selection. Related subjects: Central & South American
Geography

   River Amazon
   Image:Amazon river basin.png.jpg.epr

     Map showing the course of the Amazon, selected tributaries, and the
                   approximate extent of its drainage area

   Origin Nevado Mismi
   Mouth Atlantic Ocean
   Basin countries Brazil (62.4%), Peru (16.3%)
   Bolivia (12.0%), Colombia (6.3%)
   Ecuador (2.1%)
   Length 6,387 km (3,969 mi)
   Source elevation 5,597 m (18,360 ft)
   Avg. discharge 219,000 m³/s (7,740,000 ft³/s)
   Basin area 6,915,000 km² (2,670,000 mi²)
   A satellite image of the mouth of the Amazon River, looking south
   Enlarge
   A satellite image of the mouth of the Amazon River, looking south

   The Amazon River or River Amazon (Spanish: Río Amazonas; Portuguese:
   Rio Amazonas) of South America has a greater total flow than the next
   six largest rivers combined. It is sometimes known as The River Sea.
   The Amazon is also regarded by most geographic authorities as the
   second longest river on Earth, the longest being the Nile in Africa.

   The drainage area of the Amazon in Brazil, called the Amazon Basin, is
   the largest on Earth. If the Basin were an independent country, it
   would have more than twice the area of India.

   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. It is said that 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. This mixture of fresh and salt water is
   known as brackish water.

   This quantity of water causes the Amazon to have no clouds above the
   channel near its mouth, as shown in satellite images. These are usually
   taken in the morning, when water is colder and land is beginning to be
   much warmer. Above big rivers (the Orinoco and Caura rivers in
   Venezuela and many more have the same characteristic), cold waters
   create a high pressure air mass which make rivers easy to see through
   clouds. On the contrary, during afternoons, clouds cover most river
   channels.

   The main river (which is between approximately one and six miles wide)
   is navigable for large ocean steamers to Manaus, 1,500 km (more than
   900 miles) upriver from the mouth. Smaller ocean vessels of 3,000 tons
   and 5.5 m (18 ft) draft can reach as far as Iquitos, 3,600 km (2,250
   miles) from the sea. Smaller riverboats can reach 780 km (486 mi)
   higher as far as Achual Point. Beyond that, small boats frequently
   ascend to the Pongo de Manseriche, just above Achual Point.

   The Amazon drains an area of some 6,915,000km² (2,722,000 mile²), 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; and, after a course of about 6,400 km (4,000 mi) through
   the interior of Peru and across Brazil, it enters the Atlantic Ocean at
   the equator.

   The Amazon has changed its drainage several times, from westward in the
   early Cenozoic to its present eastward locomotion following the uplift
   of the Andes.

Amazonian Rainforest

   Amazon rainforest
   Enlarge
   Amazon rainforest

   From the east of the Andes, the Amazon Rainforest begins. It is the
   largest rainforest in the world and is of great ecological
   significance, as its biomass is capable of absorbing enormous amounts
   of carbon dioxide. Conservation of the Amazon Rainforest has been a
   major issue in recent years.

   The rainforest is supported by the extremely wet climate of the Amazon
   basin. The Amazon, and its hundreds of tributaries, flow slowly across
   the landscape, with an extremely shallow gradient sending them towards
   the sea: Manaus, 1,600 km (1,000 mi) from the Atlantic, is only 44 m
   (144 ft) above sea level.

   The biodiversity within the rainforest is extraordinary: the region is
   home to at least 2.5 million insect species, tens of thousands of
   plants, and some 2,000 birds and mammals. One fifth of all the world's
   species of birds can be found in the Amazon rainforest.

   The diversity of plant species in the Amazon basin is the highest on
   Earth. Some experts estimate that one square kilometre may contain over
   75,000 types of trees and 150,000 species of higher plants. One square
   kilometre of Amazon rainforest can contain about 90,000 tons of living
   plants.

Flooding

   A NASA satellite image of a flooded portion of the river.
   Enlarge
   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 (120 ft) and the average width can be nearly twenty-five miles. 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.

Towards the sea

   The breadth of the Amazon in some places is as much as 6 to 10 km (4 to
   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 (15
   ft) above low river, into many islands.

   At the narrows of Óbidos, 600 km (400 mi) from the sea, the Amazon
   narrows, flowing in a single streambed, a mile (1.6 km) wide and over
   200 ft (60 m). deep, through which the water rushes toward the sea at
   the speed of 6 to 8 km/h (4 to 5 mph).
   The Amazon near Manaus
   Enlarge
   The Amazon near Manaus

   From the village of Canaria at the great bend of the Amazon to the
   Negro 1,000 km (600 mi) downstream, 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
   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 (150 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
   Enlarge
   Mouth of the Amazon River

   The width of the mouth of the river is usually measured from Cabo do
   Norte to Punto Patijoca, a distance of some 330 km (207 mi); 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
   about the size of Denmark lying in the mouth of the Amazon.

Tidal bore

   Following the coast, a little to the north of Cabo do Norte, and for
   160 km (100 miles) 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 4
   fathoms (7 m). The tidal bore starts with a roar, constantly
   increasing, and advances at the rate of from 15 to 25 km/h (10 to 15
   mph), with a breaking wall of water from 1.5 to 4 m (5 to 12 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.
   Amazon River at Dawn
   Enlarge
   Amazon River at Dawn

Wildlife

   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 m.

   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 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 also supports thousands of species of fish, as well as crabs
   and turtles.

European exploration

   The first descent by a European of the Amazon from the Andes to the sea
   was made by Francisco de Orellana in 1541.

   The first ascent by a European of the river was made in 1638 by Pedro
   Teixeira, a Portuguese, who reversed the route of Orellana and reached
   Quito by way of the Napo River. He returned in 1639 with the two Jesuit
   fathers Acuña and Artieda, who had been delegated by the viceroy of
   Peru to accompany Texeira.

Name

   Before the conquest of South America, the Rio Amazonas had no general
   name; instead, indigenous peoples had names for the sections of the
   river they occupied, such as Paranaguazu, Guyerma, Solimões and others.

   In the year 1500, Vicente Yañez Pinzon, in command of a Spanish
   expedition, became the first European to explore the river, exploring
   its mouth when he discovered that the ocean off the shore was fresh
   water. Pinzon called the river the Rio Santa Maria de la Mar Dulce,
   which soon became abbreviated to Mar Dulce, and for some years, after
   1502, it was known as the Rio Grande.

   Pinzon's companions called the river El Río Marañón. The word Marañón
   is thought by some to be of indigenous origin. This idea was first
   stated in a letter from Peter Martyr to Lope Hurtado de Mendoza in
   1513. However, the word may also be derived from the Spanish word
   "maraña" — meaning a tangle, a snarl, which well represents the
   bewildering difficulties which the earlier explorers met in navigating
   not only the entrance to the Amazon, but the whole island-bordered,
   river-cut and indented coast of what is now the Brazilian state of
   Maranhão.

   The name Amazon arises from a battle which Francisco de Orellana had
   with a tribe of Tapuyas where the women of the tribe fought alongside
   the men, as was the custom among the entire tribe. Orellana derived the
   name Amazonas from the ancient Amazons of Asia and Africa described by
   Herodotus and Diodorus.

The Colonial Encounter & Amazonia

   During what many archaeologists call the formative period, Amazonian
   societies were deeply implicated 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 .

   For 350 years after the European discovery of the mighty Amazon by
   Pinzon, the Portuguese portion of the basin remained a virtually
   undisturbed wilderness, occupied by Indigenous peoples. While there is
   ample evidence for large-scale, pre-Columbian social formations,
   including chiefdoms, in many areas of Amazonia (particularly the
   inter-fluvial regions) the former indigenous inhabitants probably had
   relatively low population densities.

   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, 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
   September 7, 1867.

   Thanks in part to the mercantile development associated with steam boat
   navigation, coupled with the internationaly driven demand for natural
   rubber (1880-1920), Manáos (now Manaus), Para ( Brasil), and Iquitos,
   Peru became thriving, cosmopolitan centers of commerce and
   spectular--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 about 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 rudely 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 Negro River.
   Enlarge
   Manaus, the largest city on the Amazon, as seen from a NASA satellite
   image, surrounded by the muddy Amazon River and the dark Negro River.

   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.

   Cattle farming became a major impetus in deforestation, with military
   governments in the 1960s and 1970s heavily subsidising the creation of
   large ranches. By the 1980s the rate of destruction of the rainforest
   was dizzying, and it is estimated that over a fifth of the total area
   of the rainforest has now been clearcut. The preservation of the
   remaining forest is becoming an ever more prominent concern.

Major tributaries

   The Amazon has over 1,000 tributaries in total. Some of the more
   notable:
     * Branco
     * Casiquiare canal
     * Huallaga
     * Içá (or Putumayo)
     * 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 - Amazon, South America
    2. 3,379 km - Purus, Peru / Brazil, (2,948 km) (3,210 km)
    3. 3,239 km - Madeira, Bolivia / Brazil
    4. 2,820 km - Yapura, Colombia / Brazil
    5. 2,750 km - Tocantins, Brazil, (2,416 km) (2,640 km)
    6. 2,575 km - Araguaia, Brazil (tributary of Tocantins)
    7. 2,410 km - Juruá, Peru / Brazil
    8. 2,250 km - Negro, South America
    9. 2,100 km - Xingu, Brazil
   10. 1,900 km - Tapajós, Brazil
   11. 1,749 km - Guaporé, Brazil / Bolivia (tributary of Madeira)
   12. 1,575 km - Içá (Putumayo), South America
   13. 1,415 km - Marañón, Peru
   14. 1,300 km - Iriri, Brazil (tributary of Xingu)
   15. 1,240 km - Juruena, Brazil (tributary of Tapajós)
   16. 1,200 km - Tapajós, Brazil
   17. 1,130 km - Madre de Dios, Peru / Bolivia (tributary of Madeira)
   18. 1,100 km - Huallaga, Peru (tributary of Marañón)

Trivia

   According to a recent study , the Amazon flowed backwards about 100
   million years ago.
   Retrieved from " http://en.wikipedia.org/wiki/Amazon_River"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
