Amazon River
 |
A satellite image of the mouth of the Amazon River, looking south |
The
Amazon River or
River Amazon;
Spanish:
RÃo Amazonas,
Portuguese:
Rio Amazonas) of
South America is
the second longest river on Earth, the longest being the
Nile in Africa. The Amazon has by far the greatest total flow of any river, carrying more than the next six largest rivers combined â€" so while it may not be the
longest river, it is undoubtedly the
largest; it is also known as
The River Sea. Its
drainage area, called the
Amazon Basin, is the largest of any river system.
The quantity of fresh water released to the
Atlantic Ocean is enormous: up to 300,000 m³ per second in the rainy season. Indeed, 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.
The main river (which is usually between 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[
1] and 5.5 m (18 ft)
draft[
2] 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.
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The Amazon originates from a cliff at the Nevado Mismi, with a sole sign of a wooden cross. |
The upper Amazon comprises a series of major river systems in
Peru that flow north and south into the
Marañón and
Amazon. Among others, these include the following rivers: Morona;
Pastaza; Nucuray; Urituyacu;
Chambira; Tigre; Nanay; Napo;
Huallaga; and Ucayali. Originating in the snow-crested
Andes high above Lake Lauricocha in central Peru, the headstream of the Marañón River 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 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 primary tributaries of the Marañón River arethe Crisnejas, Chamayo, Urtcubamba, Cenepa, Santiago, Moroña, Pastaza, Huallaga, and Tigre Rivers (Cavero-Egusquiza 1941:49-51).
The ultimate source of the Amazon has only recently been firmly established as a stream on a 5,597 metre (18,363 ft) peak called
Nevado Mismi in the Peruvian
Andes, roughly 160 km west of Lake
Titicaca and 700 km S.E. of
Lima. The mountain was first suggested as the source in
1971 but this was not confirmed until
2001. The waters from Nevado Mismi flow into the
RÃo ApurÃmac 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
RÃo 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
RÃo ApurÃmac and
Ucayali, the river leaves Andean terrain and is instead surrounded by
flood plain. From this point to the
Marañón, some 1,600 km (1,000 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
Upper Amazon.
*
- Amazon biogeographyFrom 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.
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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.
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
Ã"bidos, 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).
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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 Ã"bidos, 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 Ã"bidos.
Only about 10% of the water discharged by the Amazon enters the mighty stream downstream of Ã"bidos, very little of which is from the northern slope of the valley. The drainage area of the Amazon basin above Ã"bidos 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.
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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.
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.
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
Ã"bidos 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.
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
Acuna and
Artieda, who had been delegated by the viceroy of
Peru to accompany Texeira.
Before the conquest of South America, the
RÃo de las 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 RÃo 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.
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[
3].
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 Barao Maua (
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 Para and Manáos, with steamers of 200 tons cargo capacity, a second line to make six round voyages a year between Manaós 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 Para and Manáos; 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
modern "urban growth". This was particularly the case for
Iquitos during it's late 19th and early 20th century
Rubber Bonanza zenith when this dynamic boom-town was known abroad as the
St. Louis[
4] 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.).
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.
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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.
The Amazon has over 1,000
tributaries in total. Some of the more notable are:
{
*
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 | 
