Amazon River
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The Amazon River (, ; es, Río Amazonas, pt, Rio Amazonas) in
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...
is the largest river by discharge volume of water in the world, and the disputed longest river system in the world in comparison to the
Nile The Nile, , Bohairic , lg, Kiira , Nobiin: Áman Dawū is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa and has historically been considered the longest ...
. The headwaters of the
Apurímac River The Apurímac River ( que, Apurimaq mayu; es, Río Apurímac, ; from Quechua ''apu'' 'divinity' and ''rimaq'' 'oracle, talker') rises from glacial meltwater of the ridge of the Mismi, a mountain in the Arequipa Province in the south-western ...
on
Nevado Mismi Mismi is a mountain peak of volcanic origin in the Chila mountain range in the Andes of Peru. A glacial stream on the Mismi was firmly identified as the most distant source of the Amazon River in 1996; this finding was confirmed in 2001 and ag ...
had been considered for nearly a century as the Amazon basin's most distant source, until a 2014 study found it to be the headwaters of the
Mantaro River The Mantaro River ( es, Río Mantaro, qu, Hatunmayu) is a long river running through the central region of Peru. Its Quechua name means "great river". The word "Mantaro" may be a word originally from the Asháninka language, who live downstream a ...
on the Cordillera Rumi Cruz in Peru. The Mantaro and Apurímac rivers join, and with other tributaries form the
Ucayali River The Ucayali River ( es, Río Ucayali, ) is the main headstream of the Amazon River. It rises about north of Lake Titicaca, in the Arequipa region of Peru and becomes the Amazon at the confluence of the Marañón close to Nauta city. The city of ...
, which in turn meets the
Marañón River , name_etymology = , image = Maranon.jpg , image_size = 270 , image_caption = Valley of the Marañón between Chachapoyas ( Leimebamba) and Celendín , map = Maranonrivermap.png , map_size ...
upstream of Iquitos,
Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = Seal (emblem), National seal , national_motto = "Fi ...
, forming what countries other than Brazil consider to be the
main stem In hydrology, a mainstem (or trunk) is "the primary downstream segment of a river, as contrasted to its tributaries". Water enters the mainstem from the river's drainage basin, the land area through which the mainstem and its tributaries flow.. A ...
of the Amazon. Brazilians call this section the
Solimões River Solimões () is the name often given to upper stretches of the Amazon River in Brazil from its confluence with the Rio Negro upstream to the border of Peru. Geography The Amazon / Solimões river just above the confluence of the Solimões and ...
above its confluence with the Rio Negro forming what Brazilians call the Amazon at the
Meeting of Waters The Meeting of Waters ( pt, Encontro das Águas) is the confluence between the dark ( blackwater) Rio Negro and the pale sandy-colored (whitewater) Amazon River, referred to as the Solimões River in Brazil upriver of this confluence. For th ...
( pt, Encontro das Águas) at Manaus, the largest city on the river. The Amazon River has an average discharge of about –—approximately – per year, greater than the next seven largest independent rivers combined. Two of the top ten rivers by discharge are
tributaries A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem river drain the surrounding drainag ...
of the Amazon river. The Amazon represents 20% of the global riverine discharge into oceans. The Amazon basin is the largest
drainage basin A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...
in the world, with an area of approximately . The portion of the river's drainage basin in Brazil alone is larger than any other river's basin. The Amazon enters Brazil with only one-fifth of the flow it finally discharges into the Atlantic Ocean, yet already has a greater flow at this point than the discharge of any other river.Tom Sterling: ''Der Amazonas''. Time-Life Bücher 1979, 7th German Printing, p. 19.


Etymology

The Amazon was initially known by Europeans as the Marañón, and the Peruvian part of the river is still known by that name today. It later became known as Rio Amazonas in Spanish and Portuguese. The name Rio Amazonas was reportedly given after native warriors attacked a 16th-century expedition by
Francisco de Orellana Francisco de Orellana Bejarano Pizarro y Torres de Altamirano (; 1511 – November 1546) was a Spanish explorer and conquistador. In one of the most improbably successful voyages in known history, Orellana managed to sail the length of the Amaz ...
. The warriors were led by women, reminding de Orellana of the Amazon warriors, a tribe of women warriors related to
Iranian Iranian may refer to: * Iran, a sovereign state * Iranian peoples, the speakers of the Iranian languages. The term Iranic peoples is also used for this term to distinguish the pan ethnic term from Iranian, used for the people of Iran * Iranian lan ...
Scythians The Scythians or Scyths, and sometimes also referred to as the Classical Scythians and the Pontic Scythians, were an ancient Eastern * : "In modern scholarship the name 'Sakas' is reserved for the ancient tribes of northern and eastern Centra ...
and
Sarmatians The Sarmatians (; grc, Σαρμαται, Sarmatai; Latin: ) were a large confederation of ancient Eastern Iranian equestrian nomadic peoples of classical antiquity who dominated the Pontic steppe from about the 3rd century BC to the 4th cen ...
mentioned in
Greek mythology A major branch of classical mythology, Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the Cosmogony, origin and Cosmology#Metaphysical co ...
. The word Amazon itself may be derived from the
Iranian Iranian may refer to: * Iran, a sovereign state * Iranian peoples, the speakers of the Iranian languages. The term Iranic peoples is also used for this term to distinguish the pan ethnic term from Iranian, used for the people of Iran * Iranian lan ...
compound *ha-maz-an- "(one) fighting together" or ethnonym ''*ha-mazan-'' "warriors", a word attested indirectly through a derivation, a denominal verb in
Hesychius of Alexandria Hesychius of Alexandria ( grc, Ἡσύχιος ὁ Ἀλεξανδρεύς, Hēsýchios ho Alexandreús, lit=Hesychios the Alexandrian) was a Greek grammarian who, probably in the 5th or 6th century AD,E. Dickey, Ancient Greek Scholarship (2007 ...
's gloss ("': 'to make war' in Persian"), where it appears together with the Indo-Iranian root ''*kar-'' "make" (from which
Sanskrit Sanskrit (; attributively , ; nominally , , ) is a classical language belonging to the Indo-Aryan branch of the Indo-European languages. It arose in South Asia after its predecessor languages had diffused there from the northwest in the late ...
''
karma Karma (; sa, कर्म}, ; pi, kamma, italic=yes) in Sanskrit means an action, work, or deed, and its effect or consequences. In Indian religions, the term more specifically refers to a principle of cause and effect, often descriptivel ...
'' is also derived). Other scholars claim that the name is derived from the Tupi word ''amassona'', meaning "boat destroyer"/


History


Geological history

Recent geological studies suggest that for millions of years the Amazon River used to flow in the opposite direction - from east to west. Eventually the Andes Mountains formed, blocking its flow to the Pacific Ocean, and causing it to switch directions to its current mouth in the
Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...
.


Pre-Columbian era

During what many archaeologists called the ''
formative stage Several chronologies in the archaeology of the Americas include a Formative Period or Formative stage etc. It is often sub-divided, for example into "Early", "Middle" and "Late" stages. The Formative is the third of five stages defined by Go ...
'', Amazonian societies were deeply involved in the emergence of South America's highland agrarian systems. The
trade Trade involves the transfer of goods and services from one person or entity to another, often in exchange for money. Economists refer to a system or network that allows trade as a market. An early form of trade, barter, saw the direct excha ...
with
Andean civilizations The Andean civilizations were complex societies of many cultures and peoples mainly developed in the river valleys of the coastal deserts of Peru. They stretched from the Andes of southern Colombia southward down the Andes to Chile and northwest ...
in the terrains of the
headwaters The headwaters of a river or stream is the farthest place in that river or stream from its estuary or downstream confluence with another river, as measured along the course of the river. It is also known as a river's source. Definition The ...
in the Andes formed an essential contribution to the social and religious development of higher-altitude civilizations like the
Muisca The Muisca (also called Chibcha) are an indigenous people and culture of the Altiplano Cundiboyacense, Colombia, that formed the Muisca Confederation before the Spanish conquest. The people spoke Muysccubun, a language of the Chibchan langu ...
and
Incas The Inca Empire (also known as the Incan Empire and the Inka Empire), called ''Tawantinsuyu'' by its subjects, ( Quechua for the "Realm of the Four Parts",  "four parts together" ) was the largest empire in pre-Columbian America. The adm ...
. Early human settlements were typically based on low-lying hills or mounds. Shell mounds were the earliest evidence of habitation; they represent piles of human refuse (waste) and are mainly dated between 7500 and 4000 years BC. They are associated with ceramic age cultures; no preceramic shell mounds have been documented so far by archaeologists. Artificial earth platforms for entire villages are the second type of mounds. They are best represented by the
Marajoara culture The Marajoara or Marajó culture was an ancient pre-Columbian era civilization that flourished on Marajó island at the mouth of the Amazon River in northern Brazil. In a survey, Charles C. Mann suggests the culture appeared to flourish between ...
. Figurative mounds are the most recent types of occupation. There is ample evidence that the areas surrounding the Amazon River were home to complex and large-scale indigenous societies, mainly
chiefdom A chiefdom is a form of hierarchical political organization in non-industrial societies usually based on kinship, and in which formal leadership is monopolized by the legitimate senior members of select families or 'houses'. These elites form a ...
s who developed towns and cities. Archaeologists estimate that by the time the
Spanish conquistador Conquistadors (, ) or conquistadores (, ; meaning 'conquerors') were the explorer-soldiers of the Spanish and Portuguese Empires of the 15th and 16th centuries. During the Age of Discovery, conquistadors sailed beyond Europe to the Americas, O ...
De Orellana traveled across the Amazon in 1541, more than 3 million indigenous people lived around the Amazon.Wohl, 2011, pp. 24–25. These pre-Columbian settlements created highly developed civilizations. For instance, pre-Columbian
indigenous people Indigenous peoples are culturally distinct ethnic groups whose members are directly descended from the earliest known inhabitants of a particular geographic region and, to some extent, maintain the language and culture of those original people ...
on the island of Marajó may have developed social stratification and supported a population of 100,000 people. To achieve this level of development, the indigenous inhabitants of the Amazon rainforest altered the forest's ecology by selective cultivation and the use of fire. Scientists argue that by burning areas of the forest repeatedly, the indigenous people caused the soil to become richer in nutrients. This created dark soil areas known as ''
terra preta ''Terra preta'' (, locally , literally "black soil" in Portuguese) is a type of very dark, fertile anthropogenic soil ( anthrosol) found in the Amazon Basin. It is also known as "Amazonian dark earth" or "Indian black earth". In Portuguese its f ...
de índio'' ("Indian dark earth").Wohl, 2011, p. 25. Because of the terra preta, indigenous communities were able to make land fertile and thus sustainable for the large-scale agriculture needed to support their large populations and complex social structures. Further research has hypothesized that this practice began around 11,000 years ago. Some say that its effects on forest ecology and regional climate explain the otherwise inexplicable band of lower rainfall through the Amazon basin. Many indigenous tribes engaged in constant warfare. According to James S. Olson, "The
Munduruku The Munduruku, also known as Mundurucu or Wuy Jugu or BMJ, are an indigenous people of Brazil living in the Amazon River basin. Some Munduruku communities are part of the Coatá-Laranjal Indigenous Land. They had an estimated population in 2014 ...
expansion (in the 18th century) dislocated and displaced the Kawahíb, breaking the tribe down into much smaller groups ... undurukufirst came to the attention of Europeans in 1770 when they began a series of widespread attacks on Brazilian settlements along the Amazon River."


Arrival of Europeans

In March 1500,
Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Can ...
conquistador Conquistadors (, ) or conquistadores (, ; meaning 'conquerors') were the explorer-soldiers of the Spanish and Portuguese Empires of the 15th and 16th centuries. During the Age of Discovery, conquistadors sailed beyond Europe to the Americas, O ...
Vicente Yáñez Pinzón Vicente Yáñez Pinzón () (c. 1462 – after 1514) was a Spanish navigator and explorer, the youngest of the Pinzón brothers. Along with his older brother, Martín Alonso Pinzón (''c.'' 1441 – ''c.'' 1493), who captained the '' Pinta'', h ...
was the first documented European to sail up the Amazon River. Pinzón called the stream ''Río Santa María del Mar Dulce'', later shortened to ''Mar Dulce'', literally, ''sweet sea'', because of its freshwater pushing out into the ocean. Another Spanish explorer,
Francisco de Orellana Francisco de Orellana Bejarano Pizarro y Torres de Altamirano (; 1511 – November 1546) was a Spanish explorer and conquistador. In one of the most improbably successful voyages in known history, Orellana managed to sail the length of the Amaz ...
, was the first European to travel from the origins of the upstream river basins, situated in the
Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...
, to the mouth of the river. In this journey, Orellana baptized some of the affluents of the Amazonas like Rio Negro, Napo and Jurua. The name Amazonas is thought to be taken from the native warriors that attacked this expedition, mostly women, that reminded De Orellana of the mythical female
Amazon Amazon most often refers to: * Amazons, a tribe of female warriors in Greek mythology * Amazon rainforest, a rainforest covering most of the Amazon basin * Amazon River, in South America * Amazon (company), an American multinational technolog ...
warriors from the ancient
Hellenic culture The culture of Greece has evolved over thousands of years, beginning in Minoan and later in Mycenaean Greece, continuing most notably into Classical Greece, while influencing the Roman Empire and its successor the Byzantine Empire. Other cultu ...
in Greece (see also Origin of the name).


Exploration

Gonzalo Pizarro Gonzalo Pizarro y Alonso (; 1510 – April 10, 1548) was a Spanish conquistador and younger paternal half-brother of Francisco Pizarro, the conqueror of the Inca Empire. Bastard son of Captain Gonzalo Pizarro y Rodríguez de Aguilar (senior) ( ...
set off in 1541 to explore east of Quito into the South American interior in search of '' El Dorado'', the "city of gold" and
La Canela La Canela, the Valley of Cinnamon, is a legendary location in South America. As with El Dorado, its legend grew out of expectations aroused by the voyage of Christopher Columbus. He had demonstrated to the satisfaction of his backers that gold and s ...
, the "valley of cinnamon". He was accompanied by his second-in-command
Francisco de Orellana Francisco de Orellana Bejarano Pizarro y Torres de Altamirano (; 1511 – November 1546) was a Spanish explorer and conquistador. In one of the most improbably successful voyages in known history, Orellana managed to sail the length of the Amaz ...
. After , the
Coca River The Coca River is a river in eastern Ecuador. It is a tributary A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or oc ...
joined the Napo River (at a point now known as
Puerto Francisco de Orellana Puerto Francisco de Orellana (), also known as El Coca (), is the capital of province of Orellana in eastern Ecuador. The city is located in the Amazon Rainforest at the confluence of the Coca River and the Napo River (the smaller Payamino Riv ...
); the party stopped for a few weeks to build a boat just upriver from this confluence. They continued downriver through an uninhabited area, where they could not find food. Orellana offered and was ordered to follow the Napo River, then known as ''Río de la Canela'' ("Cinnamon River"), and return with food for the party. Based on intelligence received from a captive native chief named Delicola, they expected to find food within a few days downriver by ascending another river to the north. De Orellana took about 57 men, the boat, and some canoes and left Pizarro's troops on 26 December 1541. However, De Orellana missed the confluence (probably with the Aguarico) where he was searching supplies for his men. By the time he and his men reached another village, many of them were sick from hunger and eating "noxious plants", and near death. Seven men died in that village. His men threatened to mutiny if the expedition turned back to attempt to rejoin Pizarro, the party being over 100 leagues downstream at this point. He accepted to change the purpose of the expedition to discover new lands in the name of the king of Spain, and the men built a larger boat in which to navigate downstream. After a journey of down the Napo River, they reached a further major confluence, at a point near modern Iquitos, and then followed the upper Amazon, now known as the Solimões, for a further to its confluence with the Rio Negro (near modern Manaus), which they reached on 3 June 1542. Regarding the initial mission of finding cinnamon, Pizarro reported to the king that they had found cinnamon trees, but that they could not be profitably harvested. True cinnamon (''Cinnamomum Verum'') is not native to South America. Other related cinnamon-containing plants (of the family ''Lauraceae'') are fairly common in that part of the Amazon and Pizarro probably saw some of these. The expedition reached the mouth of the Amazon on 24 August 1542, demonstrating the practical navigability of the Great River. In 1560, another Spanish
conquistador Conquistadors (, ) or conquistadores (, ; meaning 'conquerors') were the explorer-soldiers of the Spanish and Portuguese Empires of the 15th and 16th centuries. During the Age of Discovery, conquistadors sailed beyond Europe to the Americas, O ...
,
Lope de Aguirre Lope de Aguirre (; 8 November 1510 – 27 October 1561) was a Basque Spanish conquistador who was active in South America. Nicknamed ''El Loco'' ("the Madman"), he styled himself "Wrath of God, Prince of Freedom." Aguirre is best known for his ...
, may have made the second descent of the Amazon. Historians are uncertain whether the river he descended was the Amazon or the
Orinoco River The Orinoco () is one of the longest rivers in South America at . Its drainage basin, sometimes known as the Orinoquia, covers , with 76.3 percent of it in Venezuela and the remainder in Colombia. It is the fourth largest river in the wor ...
, which runs more or less parallel to the Amazon further north. Portuguese explorer
Pedro Teixeira Pedro Teixeira (b.1570-1585 - d.4 July 1641), occasionally referred to as the Conqueror of the Amazon, was a Portuguese explorer and military officer, who became, in 1637, the first European to travel up and down the entire length of the Amazon ...
was the first European to travel up the entire river. He arrived in Quito in 1637, and returned via the same route. From 1648 to 1652, Portuguese Brazilian ''
bandeirante The ''Bandeirantes'' (), literally "flag-carriers", were slavers, explorers, adventurers, and fortune hunters in early Colonial Brazil. They are largely responsible for Brazil's great expansion westward, far beyond the Tordesillas Line of 149 ...
'' António Raposo Tavares led an expedition from
São Paulo São Paulo (, ; Portuguese for 'Saint Paul') is the most populous city in Brazil, and is the capital of the state of São Paulo, the most populous and wealthiest Brazilian state, located in the country's Southeast Region. Listed by the GaWC a ...
overland to the mouth of the Amazon, investigating many of its tributaries, including the Rio Negro, and covering a distance of over . In what is currently in Brazil, Ecuador, Bolivia, Colombia, Peru, and Venezuela, several
colonial Colonial or The Colonial may refer to: * Colonial, of, relating to, or characteristic of a colony or colony (biology) Architecture * American colonial architecture * French Colonial * Spanish Colonial architecture Automobiles * Colonial (1920 au ...
and religious settlements were established along the banks of primary rivers and tributaries for trade, slaving, and
evangelization In Christianity, evangelism (or witnessing) is the act of preaching the gospel with the intention of sharing the message and teachings of Jesus Christ. Christians who specialize in evangelism are often known as evangelists, whether they are ...
among the indigenous peoples of the vast rainforest, such as the
Urarina The Urarina are an indigenous people of the Peruvian Amazon Basin ( Loreto) who inhabit the valleys of the Chambira, Urituyacu, and Corrientes Rivers. According to both archaeological and historical sources, they have resided in the Chambira ...
. In the late 1600s, Czech Jesuit Father
Samuel Fritz Samuel Fritz SJ (9 April 1654 – 20 March 1725, 1728 or 1730) was a Czech Jesuit missionary, noted for his exploration of the Amazon River and its basin. He spent most of his life preaching to Indigenous communities in the western Amazon r ...
, an apostle of the Omagus established some forty mission villages. Fritz proposed that the
Marañón River , name_etymology = , image = Maranon.jpg , image_size = 270 , image_caption = Valley of the Marañón between Chachapoyas ( Leimebamba) and Celendín , map = Maranonrivermap.png , map_size ...
must be the source of the Amazon, noting on his 1707 map that the Marañón "has its source on the southern shore of a lake that is called Lauricocha, near
Huánuco Huánuco (; qu, Wanuku) is a city in central Peru. It had a population of 196,627 as of 2017 and in 2015 it had a population of 175,068. It is the capital of the Huánuco Region and the Huánuco District. It is the seat of the diocese of Hu ...
." Fritz reasoned that the Marañón is the largest river branch one encounters when journeying upstream, and lies farther to the west than any other tributary of the Amazon. For most of the 18th–19th centuries and into the 20th century, the Marañón was generally considered the source of the Amazon.


Scientific exploration

Early scientific, zoological, and botanical exploration of the Amazon River and basin took place from the 18th century through the first half of the 19th century. *
Charles Marie de La Condamine Charles Marie de La Condamine (28 January 1701 – 4 February 1774) was a French explorer, geographer, and mathematician. He spent ten years in territory which is now Ecuador, measuring the length of a degree of latitude at the equator and pre ...
explored the river in 1743. *
Alexander von Humboldt Friedrich Wilhelm Heinrich Alexander von Humboldt (14 September 17696 May 1859) was a German polymath, geographer, naturalist, explorer, and proponent of Romantic philosophy and science. He was the younger brother of the Prussian minister, ...
, 1799–1804 * Johann Baptist von Spix and
Carl Friedrich Philipp von Martius Carl Friedrich Philipp (Karl Friedrich Philipp) von Martius (17 April 1794 – 13 December 1868) was a German botanist and explorer. Life Martius was born at Erlangen, the son of Prof Ernst Wilhelm Martius, court apothecary. He graduated PhD ...
, 1817–1820 *
Georg von Langsdorff Georg Heinrich Freiherr von Langsdorff (8 April 1774 – 9 June 1852) was a German naturalist and explorer, as well as a Russian diplomat, better known by his Russian name, Grigori Ivanovich Langsdorf. He was a naturalist and physician on the F ...
, 1826–1828 *
Henry Walter Bates Henry Walter Bates (8 February 1825, in Leicester – 16 February 1892, in London) was an English naturalist and explorer who gave the first scientific account of mimicry in animals. He was most famous for his expedition to the rainforests of ...
and Alfred Russel Wallace, 1848–1859 *
Richard Spruce Richard Spruce (10 September 1817 – 28 December 1893) was an English botanist specializing in bryology. One of the great Victorian botanical explorers, Spruce spent 15 years exploring the Amazon from the Andes to its mouth, and was one of t ...
, 1849–1864


Post-colonial exploitation and settlement

upIglesia Matriz in Iquitos, Peru The
Cabanagem The Cabanagem (; 1835–1840) was a popular revolution and pro-separatist movement that occurred in the then province of Grão-Pará, Empire of Brazil. Among the causes for this revolt were the extreme poverty of the Paraense people, oppressio ...
revolt (1835–1840) was directed against the white ruling class. It is estimated that from 30% to 40% of the population of Grão-Pará, estimated at 100,000 people, died. The population of the Brazilian portion of the Amazon basin in 1850 was perhaps 300,000, of whom about 175,000 were Europeans and 25,000 were slaves. The Brazilian Amazon's principal commercial city, Pará (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 a population between 1,000 and 1,500. All the remaining villages, as far up as
Tabatinga Tabatinga, originally Forte de São Francisco Xavier de Tabatinga, is a municipality in the Três Fronteiras area of Western Amazonas. It is in the Brazilian state of Amazonas. Its population was 67,182 (2020) and its area is 3,225 km2. T ...
, on the Brazilian frontier of Peru, were relatively small. On 6 September 1850, Emperor Pedro II of Brazil sanctioned a law authorizing steam navigation on the Amazon and gave the Viscount of Mauá (
Irineu Evangelista de Sousa Irineu is the Portuguese version of the name Irenaeus. This name is borne by: People *Irineu Calixto Couto *Irineu Evangelista de Sousa *Victor Irineu de Souza Victor Irineu de Souza (born 3 April 1989 in Belo Horizonte), or simply Victor, is ...
) the task of putting it into effect. He organised the "Companhia de Navegação e Comércio do Amazonas" in Rio de Janeiro in 1852; in the following year it commenced operations with four small steamers, the ''Monarca'' ('Monarch'), the ''Cametá'', the ''Marajó'' and the ''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 Pará and Cametá. 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, Purús, 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 31 July 1867, the government of Brazil, constantly pressed by the maritime powers and by the countries encircling the
upper Amazon The Amazon River (, ; es, Río Amazonas, pt, Rio Amazonas) in South America is the largest river by discharge volume of water in the world, and the disputed longest river system in the world in comparison to the Nile. The headwaters of t ...
basin, especially Peru, decreed the opening of the Amazon to all countries, but they limited this to certain defined points: Tabatinga – on the Amazon; Cametá – on the Tocantins; Santarém – on the Tapajós; Borba – on the Madeira, and Manaus – on the Rio Negro. The Brazilian decree took effect on 7 September 1867. Thanks in part to the mercantile development associated with steamboat navigation coupled with the internationally driven demand for
natural rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...
, the Peruvian city of Iquitos became a thriving, cosmopolitan center of commerce. Foreign companies settled in Iquitos, from where they controlled the extraction of rubber. In 1851 Iquitos had a population of 200, and by 1900 its population reached 20,000. In the 1860s, approximately 3,000 tons of rubber were being exported annually, and by 1911 annual exports had grown to 44,000 tons, representing 9.3% of Peru's exports. During the
rubber boom The Amazon rubber boom ( pt, Ciclo da borracha, ; es, Fiebre del caucho, , 1879 to 1912) was an important part of the economic and social history of Brazil and Amazonian regions of neighboring countries, being related to the extraction and comm ...
it is estimated that diseases brought by immigrants, such as
typhus Typhus, also known as typhus fever, is a group of infectious diseases that include epidemic typhus, scrub typhus, and murine typhus. Common symptoms include fever, headache, and a rash. Typically these begin one to two weeks after exposure. ...
and
malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. S ...
, killed 40,000 native Amazonians. The first direct foreign trade with Manaus 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, Purús, and many other tributaries, such as the Marañón, to ports as distant as
Nauta Nauta is a town in the northeastern part of Loreto Province in the Peruvian Amazon, roughly south of Iquitos, the provincial capital. Nauta is located on the north bank of the Marañón River, a major tributary of the Upper Amazon, a few miles ...
, Peru. By the turn of the 20th century, the exports of the Amazon basin were
India-rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...
,
cacao bean The cocoa bean (technically cocoa seed) or simply cocoa (), also called the cacao bean (technically cacao seed) or cacao (), is the dried and fully fermented seed of '' Theobroma cacao'', from which cocoa solids (a mixture of nonfat substanc ...
s,
Brazil nut The Brazil nut (''Bertholletia excelsa'') is a South American tree in the family Lecythidaceae, and it is also the name of the tree's commercially harvested edible seeds. It is one of the largest and longest-lived trees in the Amazon rainforest. ...
s and a few other products of minor importance, such as
pelts Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily guard hair on top and thick underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an insulating blanket ...
and exotic forest produce (
resin In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on n ...
s, barks, woven
hammock A hammock (from Spanish , borrowed from Taíno and Arawak ) is a sling made of fabric, rope, or netting, suspended between two or more points, used for swinging, sleeping, or resting. It normally consists of one or more cloth panels, or a wo ...
s, prized bird feathers, live animals) and extracted goods, such as
lumber Lumber is wood that has been processed into dimensional lumber, including beams and planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, wi ...
and gold.


20th-century development

Since colonial times, the Portuguese portion of the Amazon basin has remained a land largely undeveloped by agriculture and occupied by indigenous people who survived the arrival of European diseases. Four centuries after the European discovery of the Amazon river, the total cultivated area in its basin was probably less than , excluding the limited and crudely cultivated areas among the mountains at its extreme headwaters. This situation changed dramatically during the 20th century. 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 Getúlio Dornelles Vargas (; 19 April 1882 – 24 August 1954) was a Brazilian lawyer and politician who served as the 14th and 17th president of Brazil, from 1930 to 1945 and from 1951 to 1954. Due to his long and controversial tenure as Brazi ...
, with the demand for rubber from the Allied forces in World War II providing funding for the drive. In the 1960s, economic exploitation of the Amazon basin was seen as a way to fuel the "economic miracle" occurring at the time. This resulted in the development of "Operation Amazon", an economic development project that brought large-scale agriculture and ranching to Amazonia. This was done through a combination of credit and fiscal incentives. However, in the 1970s the government took a new approach with the National Integration Program (PIN). A large-scale colonization program saw families from northeastern Brazil relocated to the "land without people" in the Amazon Basin. This was done in conjunction with infrastructure projects mainly the
Trans-Amazonian Highway The Trans-Amazonian Highway (official designation BR-230, official name Rodovia Transamazônica), was introduced on September 27, 1972. It is 4,000 km long, making it the third longest highway in Brazil. It runs through the Amazon forest and ...
(''Transamazônica''). The Trans-Amazonian Highway's three pioneering highways were completed within ten years but never fulfilled their promise. Large portions of the Trans-Amazonian and its accessory roads, such as BR-319 (Manaus-
Porto Velho Porto Velho (, ''Old Port'') is the capital of the Brazilian state of Rondônia, in the upper Amazon River basin, and a Catholic Metropolitan Archbishopric. The population is 548,952 people (as of the IBGE 2021 estimation). Located on the border of ...
), are derelict and impassable in the rainy season. Small towns and villages are scattered across the forest, and because its vegetation is so dense, some remote areas are still unexplored. Many settlements grew along the road from Brasília to Belém with the highway and National Integration Program, however, the program failed as the settlers were unequipped to live in the delicate rainforest ecosystem. This, although the government believed it could sustain millions, instead could sustain very few. With a population of 1.9 million people in 2014, Manaus is the largest city on the Amazon. Manaus alone makes up approximately 50% of the population of the largest Brazilian state of Amazonas. The racial makeup of the city is 64%
pardo ''Pardos'' (feminine ''pardas'') is a term used in the former Portuguese and Spanish colonies in the Americas to refer to the triracial descendants of Southern Europeans, Amerindians and West Africans. In some places they were defined as ne ...
(mulatto and mestizo) and 32%
white White is the lightest color and is achromatic (having no hue). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully reflect and scatter all the visible wavelengths of light. White o ...
. Although the Amazon river remains undammed, around 412 dams are in operation in the Amazon's tributary rivers. From these 412 dams, 151 are constructed over six of the main tributary rivers that drain into the Amazon. Since only 4% of the Amazon's hydropower potential has been developed in countries like Brazil, more damming projects are underway and hundreds more are planned. After witnessing the negative effects of environmental degradation, sedimentation, navigation and flood control caused by the Three Gorges Dam in the Yangtze River, scientists are worried that constructing more dams in the Amazon will harm its biodiversity in the same way by "blocking fish-spawning runs, reducing the flows of vital oil nutrients and clearing forests". Damming the Amazon River could potentially bring about the "end of free flowing rivers" and contribute to an "
ecosystem collapse An ecosystem is considered collapsed when its unique biotic (characteristic biota) or abiotic features are lost from all previous occurrences. Ecosystem collapse causes ecological collapse within a system; essentially altering its stability, re ...
" that will cause major social and environmental problems.


Course


Origins

The most distant source of the Amazon was thought to be in the Apurímac river drainage for nearly a century. Such studies continued to be published even recently, such as in 1996, 2001, 2007, and 2008, where various authors identified the snowcapped
Nevado Mismi Mismi is a mountain peak of volcanic origin in the Chila mountain range in the Andes of Peru. A glacial stream on the Mismi was firmly identified as the most distant source of the Amazon River in 1996; this finding was confirmed in 2001 and ag ...
peak, located roughly west of
Lake Titicaca Lake Titicaca (; es, Lago Titicaca ; qu, Titiqaqa Qucha) is a large freshwater lake in the Andes mountains on the border of Bolivia and Peru. It is often called the highest navigable lake in the world. By volume of water and by surface area, i ...
and southeast of
Lima Lima ( ; ), originally founded as Ciudad de Los Reyes (City of The Kings) is the capital and the largest city of Peru. It is located in the valleys of the Chillón, Rímac and Lurín Rivers, in the desert zone of the central coastal part of ...
, as the most distant source of the river. From that point, Quebrada Carhuasanta emerges from Nevado Mismi, joins Quebrada Apacheta and soon forms Río Lloqueta which becomes Río Hornillos and eventually joins the Río Apurímac. A 2014 study by Americans James Contos and Nicolas Tripcevich in ''
Area Area is the quantity that expresses the extent of a region on the plane or on a curved surface. The area of a plane region or ''plane area'' refers to the area of a shape or planar lamina, while '' surface area'' refers to the area of an ope ...
'', a peer-reviewed journal of the Royal Geographical Society, however, identifies the most distant source of the Amazon as actually being in the Río Mantaro drainage. A variety of methods were used to compare the lengths of the Mantaro river vs. the Apurímac river from their most distant source points to their confluence, showing the longer length of the Mantaro. Then distances from Lago Junín to several potential source points in the uppermost Mantaro river were measured, which enabled them to determine that the Cordillera Rumi Cruz was the most distant source of water in the Mantaro basin (and therefore in the entire Amazon basin). The most accurate measurement method was direct GPS measurement obtained by kayak descent of each of the rivers from their source points to their confluence (performed by Contos). Obtaining these measurements was difficult given the class IV–V nature of each of these rivers, especially in their lower "Abyss" sections. Ultimately, they determined that the most distant point in the Mantaro drainage is nearly 80 km farther upstream compared to Mt. Mismi in the Apurímac drainage, and thus the maximal length of the Amazon river is about 80 km longer than previously thought. Contos continued downstream to the ocean and finished the first complete descent of the Amazon river from its newly identified source (finishing November 2012), a journey repeated by two groups after the news spread. After about , the Apurímac then joins Río Mantaro to form the Ene, which joins the Perene to form the Tambo, which joins the
Urubamba River The Urubamba River or Vilcamayo River (possibly from Quechua ''Willkamayu'', for "sacred river") is a river in Peru. Upstream it is called Vilcanota River (possibly from Aymara ''Willkanuta'', for "house of the sun"). Within the La Convención ...
to form the Ucayali. After the confluence of Apurímac and Ucayali, the river leaves Andean terrain and is surrounded by
floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...
. From this point to the confluence of the Ucayali and the Marañón, some , the forested banks are just above the water and are inundated long before the river attains its maximum flood stage. The low river banks are interrupted by only a few hills, and the river enters the enormous
Amazon rainforest The Amazon rainforest, Amazon jungle or ; es, Selva amazónica, , or usually ; french: Forêt amazonienne; nl, Amazoneregenwoud. In English, the names are sometimes capitalized further, as Amazon Rainforest, Amazon Forest, or Amazon Jungle. ...
.


The Upper Amazon or Solimões

Although the Ucayali–Marañón confluence is the point at which most geographers place the beginning of the Amazon River proper, in Brazil the river is known at this point as the '' Solimões das Águas''. 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". The Amazon proper runs mostly through Brazil and Peru, and is part of the border between Colombia and Perú. It has a series of major tributaries in
Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...
,
Ecuador Ecuador ( ; ; Quechua: ''Ikwayur''; Shuar: ''Ecuador'' or ''Ekuatur''), officially the Republic of Ecuador ( es, República del Ecuador, which literally translates as "Republic of the Equator"; Quechua: ''Ikwadur Ripuwlika''; Shuar: ''Eku ...
and
Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = Seal (emblem), National seal , national_motto = "Fi ...
, some of which flow into the Marañón and
Ucayali The Ucayali River ( es, Río Ucayali, ) is the main headstream of the Amazon River. It rises about north of Lake Titicaca, in the Arequipa region of Peru and becomes the Amazon at the confluence of the Marañón close to Nauta city. The city ...
, and others directly into the Amazon proper. These include rivers Putumayo, Caquetá, Vaupés, Guainía,
Morona The Morona River is a tributary to the Marañón River, and flows parallel to the Pastaza River and immediately to the west of it, and is the last stream of any importance on the northern side of the Amazon before reaching the Pongo de Manseriche. ...
, Pastaza, Nucuray, Urituyacu,
Chambira The Chambira River is a major tributary of the Marañón River, and has been the traditional territory of the Urarina peoples for at least the past 350 years, if not longer. Located in the Amazon jungle of Peru, otherwise known as the Selva, the Ch ...
, Tigre, Nanay, Napo, and Huallaga. At some points, the river divides into anabranches, or multiple channels, often very long, with inland and lateral
channels Channel, channels, channeling, etc., may refer to: Geography * Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a narrow body of water. Australia * Channel Country, region of outback Austral ...
, all connected by a complicated system of natural canals, cutting the low, flat ''igapó'' lands, which are never more than above low river, into many islands. From the town of Canaria at the great bend of the Amazon to the Negro, vast areas of land 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.


The Lower Amazon

The Lower Amazon begins where the darkly colored waters of the Rio Negro meets the sandy-colored Rio Solimões (the upper Amazon), and for over these waters run side by side without mixing. At Óbidos, a bluff above the river is backed by low hills. The lower Amazon seems to have once been a
gulf A gulf is a large inlet from the ocean into the landmass, typically with a narrower opening than a bay, but that is not observable in all geographic areas so named. The term gulf was traditionally used for large highly-indented navigable bodies ...
of the Atlantic Ocean, the waters of which washed the cliffs near Óbidos. Only about 10% of the Amazon's water enters 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 , and, below, only about (around 20%), exclusive of the of the Tocantins basin. The
Tocantins River The Tocantins River ( pt, Rio Tocantins, link=no , , Parkatêjê: ''Pyti'' ɨˈti is a river in Brazil, the central fluvial artery of the country. In the Tupi language, its name means " toucan's beak" (''Tukã'' for "toucan" and ''Ti'' for "beak ...
enters the southern portion of the
Amazon delta Amazon Delta ('' pt, delta do Amazonas'' is a huge river delta formed by the Amazon River and Tocantins River (through the Pará River distributary channel), in northern South America. It is located in the Brazilian states of Pará and Amapá and ...
. In the lower reaches of the river, the north bank consists of a series of steep, table-topped hills extending for about from opposite the mouth of the Xingu as far as Monte Alegre. These hills are cut down to a kind of
terrace Terrace may refer to: Landforms and construction * Fluvial terrace, a natural, flat surface that borders and lies above the floodplain of a stream or river * Terrace, a street suffix * Terrace, the portion of a lot between the public sidewalk an ...
which lies between them and the river. On the south bank, above the Xingu, a line of low bluffs bordering the floodplain extends nearly to Santarém in a series of gentle curves before they bend to the southwest, and, abutting upon the lower Tapajós, merge into the bluffs which form the terrace margin of the Tapajós river valley.


Mouth

Belém Belém (; Portuguese for Bethlehem; initially called Nossa Senhora de Belém do Grão-Pará, in English Our Lady of Bethlehem of Great Pará) often called Belém of Pará, is a Brazilian city, capital and largest city of the state of Pará in t ...
is the major city and port at the mouth of the river at the Atlantic Ocean. The definition of where exactly the mouth of the Amazon is located, and how wide it is, is a matter of dispute, because of the area's peculiar geography. The
Pará Pará is a state of Brazil, located in northern Brazil and traversed by the lower Amazon River. It borders the Brazilian states of Amapá, Maranhão, Tocantins, Mato Grosso, Amazonas and Roraima. To the northwest are the borders of Guyana ...
and the Amazon are connected by a series of river channels called ''furos'' near the town of Breves; between them lies
Marajó Marajó () is a large coastal island in the state of Pará, Brazil. It is the main and largest of the islands in the Marajó Archipelago. Marajó Island is separated from the mainland by Marajó Bay, Pará River, smaller rivers (especially ...
, the world's largest combined river/sea island. If the Pará river and the Marajó island ocean frontage are included, the Amazon
estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...
is some wide. In this case, the width of the mouth of the river is usually measured from Cabo Norte, the cape located straight east of
Pracuúba Pracuúba () is a municipality located in the mideast of the state of Amapá in Brazil. It became an independent municipality in 1992. The town can be accessed from the BR-156 highway. Location The population of Pracuúba is 5,246 and its area is ...
in the Brazilian state of Amapá, to Ponta da Tijoca near the town of Curuçá, in the state of
Pará Pará is a state of Brazil, located in northern Brazil and traversed by the lower Amazon River. It borders the Brazilian states of Amapá, Maranhão, Tocantins, Mato Grosso, Amazonas and Roraima. To the northwest are the borders of Guyana ...
. A more conservative measurement excluding the Pará river estuary, from the mouth of the Araguari River to Ponta do Navio on the northern coast of Marajó, would still give the mouth of the Amazon a width of over . If only the river's main channel is considered, between the islands of Curuá (state of Amapá) and Jurupari (state of Pará), the width falls to about . The plume generated by the river's discharge covers up to 1.3 million km2 and is responsible for muddy bottoms influencing a wide area of the tropical north Atlantic in terms of salinity, pH, light penetration, and sedimentation.


Lack of bridges

There are no
bridge A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually somethi ...
s across the entire width of the river. This is not because the river would be too wide to bridge; for most of its length, engineers could build a bridge across the river easily. For most of its course, the river flows through the Amazon Rainforest, where there are very few roads and cities. Most of the time, the crossing can be done by a ferry. The
Manaus Iranduba Bridge The Journalist Phelippe Dahsou Bridge ( pt, Ponte Rio Negro) is the fourth longest bridge in Brazil at long with a cable-stayed bridge section of 400-metre (1,132 ft) over the Rio Negro that links the cities of Manaus and Iranduba in the sta ...
linking the cities of Manaus and Iranduba spans the Rio Negro, the second-largest tributary of the Amazon, just before their confluence.


Dispute regarding length

While debate as to whether the Amazon or
the Nile The Nile, , Bohairic , lg, Kiira , Nobiin: Áman Dawū is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa and has historically been considered the longest riv ...
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 reported as being anywhere between and long. It is often said to be "at least" long. The Nile is reported to be anywhere from . Often it is said to be "about" long. There are several factors that can affect these measurements, such as the position of the geographical source and the mouth, the scale of measurement, and the length measuring techniques (for details see also
List of rivers by length This is a list of the longest rivers on Earth. It includes river systems over in length. Definition of length There are many factors, such as the identification of the source, the identification or the definition of the mouth, and the scale o ...
). In July 2008, the Brazilian Institute for Space Research (INPE) published a news article on their webpage, claiming that the Amazon River was longer than
the Nile The Nile, , Bohairic , lg, Kiira , Nobiin: Áman Dawū is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa and has historically been considered the longest riv ...
. The Amazon's length was calculated as , taking the Apacheta Creek as its source. Using the same techniques, the length of the Nile was calculated as , which is longer than previous estimates but still shorter than the Amazon. The results were reached by measuring the Amazon downstream to the beginning of the tidal estuary of ''Canal do Sul'' and then, after a sharp turn back, following tidal canals surrounding the isle of Marajó and finally including the marine waters of the ''Río Pará'' bay in its entire length. According to an earlier article on the webpage of
the National Geographic ''National Geographic'' (formerly the ''National Geographic Magazine'', sometimes branded as NAT GEO) is a popular American monthly magazine published by National Geographic Partners. Known for its photojournalism, it is one of the most widel ...
, the Amazon's length was calculated as by a Brazilian scientist. In June 2007, Guido Gelli, director of science at the Brazilian Institute of Geography and Statistics (IBGE), told London's
Telegraph Telegraphy is the long-distance transmission of messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas p ...
Newspaper that it could be considered that the Amazon was the longest river in the world. However, according to the above sources, none of the two results was published, and questions were raised about the researchers' methodology. In 2009, a peer-reviewed article, was published, concluding that the Nile is longer than the Amazon by stating a length of for the Nile and for the Amazon, measured by using a combination of satellite image analysis and field investigations to the source regions. According to the
Encyclopædia Britannica The (Latin for "British Encyclopædia") is a general knowledge English-language encyclopaedia. It is published by Encyclopædia Britannica, Inc.; the company has existed since the 18th century, although it has changed ownership various t ...
, the final length of the Amazon remains open to interpretation and continued debate.


Watershed

The Amazon basin, the largest in the world, covers about 40% of South America, an area of approximately . It drains from west to east, from Iquitos in Peru, across Brazil to the Atlantic. It gathers its waters from 5 degrees north latitude to 20 degrees south latitude. Its most remote sources are found on the inter-
Andean The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S l ...
plateau, just a short distance from the
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
. The Amazon River and its tributaries are characterised by extensive forested areas that become flooded every rainy season. Every year, the river rises more than , flooding the surrounding forests, known as '' várzea'' ("flooded forests"). The Amazon's flooded forests are the most extensive example of this habitat type in the world. In an average
dry season The dry season is a yearly period of low rainfall, especially in the tropics. The weather in the tropics is dominated by the tropical rain belt, which moves from the northern to the southern tropics and back over the course of the year. The te ...
, of land are water-covered, while in the
wet season The wet season (sometimes called the Rainy season) is the time of year when most of a region's average annual rainfall occurs. It is the time of year where the majority of a country's or region's annual precipitation occurs. Generally, the sea ...
, the flooded area of the Amazon basin rises to . The quantity of water released by the Amazon to the Atlantic Ocean is enormous: up to in the rainy season, with an average of from 1973 to 1990. The Amazon is responsible for about 20% of the Earth's fresh water entering the ocean. The river pushes a vast plume of fresh water into the ocean. The plume is about long and between wide. The fresh water, being lighter, flows on top of the seawater, diluting the salinity and altering the colour of the ocean surface over an area up to in extent. For centuries ships have reported fresh water near the Amazon's mouth yet well out of sight of land in what otherwise seemed to be the open ocean. The Atlantic has sufficient wave and tidal energy to carry most of the Amazon's
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...
s out to sea, thus the Amazon does not form a true delta. The great deltas of the world are all in relatively protected bodies of water, while the Amazon empties directly into the turbulent Atlantic. There is a natural water union between the Amazon and the Orinoco basins, the so-called
Casiquiare canal The Casiquiare river () is a distributary of the upper Orinoco flowing southward into the Rio Negro, in Venezuela, South America. As such, it forms a unique natural canal between the Orinoco and Amazon river systems. It is the world's largest ...
. The Casiquiare is a river distributary of the upper Orinoco, which flows southward into the Rio Negro, which in turn flows into the Amazon. The Casiquiare is the largest river on earth that links two major river systems, a so-called
bifurcation Bifurcation or bifurcated may refer to: Science and technology * Bifurcation theory, the study of sudden changes in dynamical systems ** Bifurcation, of an incompressible flow, modeled by squeeze mapping the fluid flow * River bifurcation, the ...
.


Flooding

Not all of the Amazon's tributaries flood at the same time of the year. Many branches begin flooding in November and might continue to rise until June. The rise of the Rio Negro starts in February or March and begins to recede in June. The Madeira River rises and falls two months earlier than most of the rest of the Amazon river. The depth of the Amazon between
Manacapuru Manacapuru (''Munychapur'') is a municipality located in the Brazilian state of Amazonas. Population The population of Manacapuru was 98,502 (2020) and its area is 7,329 km². The city is one of the biggest in the state. It is located abou ...
and Óbidos has been calculated as between . At Manacapuru, the Amazon's water level is only about above
mean sea level There are several kinds of mean in mathematics, especially in statistics. Each mean serves to summarize a given group of data, often to better understand the overall value (magnitude and sign) of a given data set. For a data set, the '' ari ...
. More than half of the water in the Amazon downstream of Manacapuru is below sea level. In its lowermost section, the Amazon's depth averages , in some places as much as . The main river is navigable for large ocean steamers to Manaus, upriver from the mouth. Smaller ocean vessels below 9000 tons and with less than
draft Draft, The Draft, or Draught may refer to: Watercraft dimensions * Draft (hull), the distance from waterline to keel of a vessel * Draft (sail), degree of curvature in a sail * Air draft, distance from waterline to the highest point on a vesse ...
can reach as far as Iquitos, Peru, from the sea. Smaller riverboats can reach higher, as far as Achual Point. Beyond that, small boats frequently ascend to the
Pongo de Manseriche The Pongo de Manseriche is a gorge in northwest Peru. The Marañón River runs through this gorge (and water gap) before it reaches the Amazon Basin. The Pongo ('gate' in Quechua) de Manseriche is 3 miles (4.8 km) long, located at 4° 27 ...
, just above Achual Point in Peru. Annual flooding occurs in late northern latitude winter at high tide when the incoming waters of the
Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...
are funnelled into the Amazon delta. The resulting undular
tidal bore Tidal is the adjectival form of tide. Tidal may also refer to: * ''Tidal'' (album), a 1996 album by Fiona Apple * Tidal (king), a king involved in the Battle of the Vale of Siddim * TidalCycles, a live coding environment for music * Tidal (serv ...
is called the ''
pororoca The Pororoca (, ) is a tidal bore, with waves up to high that travel as much as inland upstream on the Amazon River and adjacent rivers. Its name might come from the indigenous Tupi language, where it could translate into "great roar". It could b ...
'', with a leading wave that can be up to high and travel up to inland.


Geology

The Amazon River originated as a transcontinental river in the
Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...
epoch between 11.8 million and 11.3 million years ago and took its present shape approximately 2.4 million years ago in the Early
Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...
. The proto-Amazon during the
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
flowed west, as part of a proto-Amazon-Congo river system, from the interior of present-day Africa when the continents were connected, forming western Gondwana. 80 million years ago, the two continents split. Fifteen million years ago, the main
tectonic uplift Tectonic uplift is the geologic uplift of Earth's surface that is attributed to plate tectonics. While isostatic response is important, an increase in the mean elevation of a region can only occur in response to tectonic processes of crustal th ...
phase of the Andean chain started. This tectonic movement is caused by the subduction of the Nazca Plate underneath the South American Plate. The rise of the Andes and the linkage of the Brazilian and Guyana bedrock shields, blocked the river and caused the Amazon Basin to become a vast inland sea. Gradually, this inland sea became a massive swampy, freshwater lake and the marine inhabitants adapted to life in freshwater. Eleven to ten million years ago, waters worked through the
sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...
from the west and the Amazon began to flow eastward, leading to the emergence of the Amazon rainforest. During
glacial period A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betwe ...
s, sea levels dropped and the great Amazon lake rapidly drained and became a river, which would eventually become the disputed world's longest, draining the most extensive area of rainforest on the planet. Paralleling the Amazon River is a large aquifer, dubbed the
Hamza River The Hamza River (Portuguese: ''Rio Hamza'') is an unofficial name for what seems to be a slowly flowing aquifer in Brazil and Peru, approximately long at a depth of nearly . Its discovery was announced in 2011 at a meeting of the Geophysical Societ ...
, the discovery of which was made public in August 2011.


Protected areas


Flora and fauna


Flora


Fauna

More than one-third of all known species in the world live in the
Amazon rainforest The Amazon rainforest, Amazon jungle or ; es, Selva amazónica, , or usually ; french: Forêt amazonienne; nl, Amazoneregenwoud. In English, the names are sometimes capitalized further, as Amazon Rainforest, Amazon Forest, or Amazon Jungle. ...
. It is the richest tropical forest in the world in terms of
biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
. In addition to thousands of species of fish, the river supports crabs, algae, and turtles.


Mammals

Along with the Orinoco, the Amazon is one of the main habitats of the ''
boto Boto is a Portuguese name given to several types of dolphins and river dolphins native to the Amazon and the Orinoco River tributaries. A few botos exist exclusively in fresh water, and these are often considered primitive dolphins. Classificatio ...
'', also known as the
Amazon river dolphin The Amazon river dolphin (''Inia geoffrensis''), also known as the boto, bufeo or pink river dolphin, is a species of toothed whale classified in the family Iniidae. Three subspecies are currently recognized: ''I. g. geoffrensis'' (Amazon river ...
(''Inia geoffrensis''). It is the largest species of
river dolphin River dolphins are a polyphyletic group of fully aquatic mammals that reside exclusively in freshwater or brackish water. They are an informal grouping of dolphins, which itself is a paraphyletic group within the infraorder Cetacea. Extant riv ...
, and it can grow to lengths of up to . The colour of its skin changes with age; young animals are gray, but become pink and then white as they mature. The dolphins use echolocation to navigate and hunt in the river's tricky depths. The ''boto'' is the subject of a legend in Brazil about a
dolphin A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the ...
that turns into a man and seduces maidens by the riverside. The
tucuxi The tucuxi (''Sotalia fluviatilis''), alternatively known in Peru ''bufeo gris'' or ''bufeo negro'', is a species of freshwater dolphin found in the rivers of the Amazon basin. The word ''tucuxi'' is derived from the Tupi language word ''tuchu ...
(''Sotalia fluviatilis''), also a dolphin species, is found both in the rivers of the Amazon basin and in the coastal waters of South America. The Amazonian manatee (''Trichechus inunguis''), also known as "seacow", is found in the northern Amazon River basin and its tributaries. It is a mammal and a herbivore. Its population is limited to freshwater habitats, and, unlike other manatees, it does not venture into saltwater. It is classified as vulnerable by the
International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
. The Amazon and its tributaries are the main habitat of the
giant otter The giant otter or giant river otter (''Pteronura brasiliensis'') is a South American carnivorous mammal. It is the longest member of the weasel family, Mustelidae, a globally successful group of predators, reaching up to . Atypical of muste ...
(''Pteronura brasiliensis''). Sometimes known as the "river wolf," it is one of South America's top carnivores. Because of habitat destruction and hunting, its population has dramatically decreased. It is now listed on Appendix I of the Convention on International Trade in Endangered Species (CITES), which effectively bans international trade.


Reptiles

The
Anaconda Anacondas or water boas are a group of large snakes of the genus '' Eunectes''. They are found in tropical South America. Four species are currently recognized. Description Although the name applies to a group of snakes, it is often used ...
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. Species of
caiman A caiman (also cayman as a variant spelling) is an alligatorid belonging to the subfamily Caimaninae, one of two primary lineages within the Alligatoridae family, the other being alligators. Caimans inhabit Mexico, Central and South America f ...
s, that are related to alligators and other crocodilians, also inhabit the Amazon as do varieties of turtles.Cuvier's smooth-fronted caiman (''Paleosuchus palpebrosus'')


Birds

The types of birds that pass by or live in the amazon river are toucans, harpy eagles, and much more variations of birds.


Fish

The Amazonian fish fauna is the centre of diversity for
neotropical fishes The freshwater fish of tropical South and Central America represent one of the most diverse and extreme aquatic ecosystems on Earth, with more than 5,600 species, representing about 10% all living vertebrate species. The exceptional diversity of sp ...
, some of which are popular aquarium specimens like the
neon tetra The neon tetra (''Paracheirodon innesi'') is a Freshwater fish of the characin family (family Characidae) of order Characiformes. The type species of its genus, it is native to blackwater and clearwater streams in the Amazon basin of Sout ...
and the
freshwater angelfish ''Pterophyllum'' is a small genus of freshwater fish from the family Cichlidae known to most aquarists as angelfish. All ''Pterophyllum'' species originate from the Amazon Basin, Orinoco Basin and various rivers in the Guiana Shield in trop ...
. More than 5,600 species were known , and approximately fifty new species are discovered each year. The
arapaima The arapaima, pirarucu, or paiche is any large species of bonytongue in the genus ''Arapaima'' native to the Amazon and Essequibo basins of South America. ''Arapaima'' is the type genus of the subfamily Arapaiminae within the family Osteoglossi ...
, known in Brazil as the ''pirarucu'', is a South American tropical
freshwater fish Freshwater fish are those that spend some or all of their lives in fresh water, such as rivers and lakes, with a salinity of less than 1.05%. These environments differ from marine conditions in many ways, especially the difference in levels of ...
, one of the largest freshwater fish in the world, with a length of up to . Another Amazonian freshwater fish is the
arowana Arowanas are freshwater bony fish of the subfamily Osteoglossinae, also known as bony tongues (the latter name is now often reserved for Arapaiminae). In this family of fish, the head is bony and the elongated body is covered by large, heavy sc ...
(or ''aruanã'' in Portuguese), such as the
silver arowana The silver arowana (''Osteoglossum bicirrhosum'') is a South American freshwater bony fish of the family Osteoglossidae. Silver arowanas are sometimes kept in aquariums, but they are predatory and require a very large tank. The generic name ' ...
('' Osteoglossum bicirrhosum''), which is a predator and very similar to the arapaima, but only reaches a length of . Also present in large numbers is the notorious
piranha A piranha or piraña (, , or ; or , ) is one of a number of freshwater fish in the family Serrasalmidae, or the subfamily Serrasalminae within the tetra family, Characidae in order Characiformes. These fish inhabit South American rivers, fl ...
, an omnivorous fish that congregates in large schools and may attack livestock. There are approximately 30 to 60 species of piranha. The candirú, native to the Amazon River, is a species of parasitic fresh water
catfish Catfish (or catfishes; order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the three largest species alive ...
in the family
Trichomycteridae Trichomycteridae is a family of catfishes commonly known as pencil catfishes or parasitic catfishes. This family includes the candiru fish (''Vandellia cirrhosa''), feared by some people for its alleged habit of entering into the urethra of hum ...
, just one of more than 1200 species of catfish in the Amazon basin. Other catfish 'walk' overland on their ventral fins, while the kumakuma (''Brachyplatystoma filamentosum''), aka ''piraiba'' or "goliath catfish", can reach in length and in weight. The
electric eel The electric eels are a genus, ''Electrophorus'', of neotropical freshwater fish from South America in the family Gymnotidae. They are known for their ability to stun their prey by generating electricity, delivering shocks at up to 860 volt ...
(''Electrophorus electricus'') and more than 100 species of electric fishes ( Gymnotiformes) inhabit the Amazon basin. River stingrays (
Potamotrygonidae River stingrays or freshwater stingrays are Neotropical freshwater fishes of the family Potamotrygonidae in the order Myliobatiformes, one of the four orders of batoids, cartilaginous fishes related to sharks. They are found in rivers in tropic ...
) are also known. The
bull shark The bull shark (''Carcharhinus leucas''), also known as the Zambezi shark (informally zambi) in Africa and Lake Nicaragua shark in Nicaragua, is a species of requiem shark commonly found worldwide in warm, shallow waters along coasts and in ri ...
(''Carcharhinus leucas'') has been reported up the Amazon River at Iquitos in Peru.


Butterflies


Microbiota

Freshwater microbes are generally not very well known, even less so for a pristine ecosystem like the Amazon. Recently,
metagenomics Metagenomics is the study of genetic material recovered directly from environmental or clinical samples by a method called sequencing. The broad field may also be referred to as environmental genomics, ecogenomics, community genomics or microb ...
has provided answers to what kind of microbes inhabit the river. The most important microbes in the Amazon River are
Actinomycetota The ''Actinomycetota'' (or ''Actinobacteria'') are a phylum of all gram-positive bacteria. They can be terrestrial or aquatic. They are of great economic importance to humans because agriculture and forests depend on their contributions to s ...
,
Alphaproteobacteria Alphaproteobacteria is a class of bacteria in the phylum Pseudomonadota (formerly Proteobacteria). The Magnetococcales and Mariprofundales are considered basal or sister to the Alphaproteobacteria. The Alphaproteobacteria are highly diverse and ...
,
Betaproteobacteria Betaproteobacteria are a class of Gram-negative bacteria, and one of the eight classes of the phylum Pseudomonadota (synonym Proteobacteria). The ''Betaproteobacteria'' are a class comprising over 75 genera and 400 species of bacteria. Togeth ...
, Gammaproteobacteria and
Thermoproteota The Thermoproteota (also known as crenarchaea) are archaea that have been classified as a phylum of the Archaea domain. Initially, the Thermoproteota were thought to be sulfur-dependent extremophiles but recent studies have identified characteris ...
.


Major tributaries

The Amazon has over 1,100
tributaries A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem river drain the surrounding drainag ...
, twelve of which are over long. Some of the more notable ones are: * Branco *
Casiquiare canal The Casiquiare river () is a distributary of the upper Orinoco flowing southward into the Rio Negro, in Venezuela, South America. As such, it forms a unique natural canal between the Orinoco and Amazon river systems. It is the world's largest ...
* Caquetá * Huallaga * Putumayo (or Içá River) * Javary (or Yavarí) * Juruá * Madeira * Marañón *
Morona The Morona River is a tributary to the Marañón River, and flows parallel to the Pastaza River and immediately to the west of it, and is the last stream of any importance on the northern side of the Amazon before reaching the Pongo de Manseriche. ...
* Nanay * Napo *
Negro In the English language, ''negro'' is a term historically used to denote persons considered to be of Black African heritage. The word ''negro'' means the color black in both Spanish and in Portuguese, where English took it from. The term can be ...
* Pastaza * Purús * Tambo *
Tapajós The Tapajós ( pt, Rio Tapajós ) is a river in Brazil. It runs through the Amazon Rainforest and is a major tributary of the Amazon River. When combined with the Juruena River, the Tapajós is approximately long. It is one of the largest clearw ...
* Tigre *
Tocantins Tocantins () is one of the 26 states of Brazil. It is the newest state, formed in 1988 and encompassing what had formerly been the northern two-fifths of the state of Goiás. Tocantins covers and had an estimated population of 1,496,880 in 20 ...
*
Trombetas The Trombetas is a large river on the northern side of the Amazon River. Course The Trombetas is long, and is navigable by 500 ton vessels for a stretch of . The Trombetas river gives birth to very many rivers, including the Anamu river. It is ...
*
Ucayali The Ucayali River ( es, Río Ucayali, ) is the main headstream of the Amazon River. It rises about north of Lake Titicaca, in the Arequipa region of Peru and becomes the Amazon at the confluence of the Marañón close to Nauta city. The city ...
* Xingu * Yapura


List of major tributaries

The main river and tributaries are (sorted in order from the confluence of Ucayali and Marañón rivers to the mouth):


List by length

# () – Amazon, South America # – Madeira, Bolivia/Brazil # – Purús, Peru/Brazil # – Japurá or Caquetá, Colombia/Brazil # –
Tocantins Tocantins () is one of the 26 states of Brazil. It is the newest state, formed in 1988 and encompassing what had formerly been the northern two-fifths of the state of Goiás. Tocantins covers and had an estimated population of 1,496,880 in 20 ...
, Brazil # – Araguaia, Brazil (tributary of Tocantins) # – Juruá, Peru/Brazil # – Rio Negro, Brazil/Venezuela/Colombia # –
Tapajós The Tapajós ( pt, Rio Tapajós ) is a river in Brazil. It runs through the Amazon Rainforest and is a major tributary of the Amazon River. When combined with the Juruena River, the Tapajós is approximately long. It is one of the largest clearw ...
, Brazil # – Xingu, Brazil # –
Ucayali River The Ucayali River ( es, Río Ucayali, ) is the main headstream of the Amazon River. It rises about north of Lake Titicaca, in the Arequipa region of Peru and becomes the Amazon at the confluence of the Marañón close to Nauta city. The city of ...
, Peru # – Guaporé, Brazil/Bolivia (tributary of Madeira) # – Içá (Putumayo), Ecuador/Colombia/Peru # – Marañón, Peru # –
Teles Pires The Teles Pires ( pt, Rio São Manuel) is a long river in Brazil. The river flows through the state of Mato Grosso and its lower part marks the border between the states of Mato Grosso and Pará. At its mouth it joins Juruena River and together ...
, Brazil (tributary of Tapajós) # – Iriri, Brazil (tributary of Xingu) # – Juruena, Brazil (tributary of Tapajós) # – Madre de Dios, Peru/Bolivia (tributary of Madeira) # – Huallaga, Peru (tributary of Marañón)


List by inflow to the Amazon


See also

* Amazon natural region *
Peruvian Amazonia Peruvian Amazonia ( es, Amazonía del Perú) is the area of the Amazon rainforest included within the country of Peru, from east of the Andes to the borders with Ecuador, Colombia, Brazil and Bolivia. This region comprises 60% of the country and ...


Notes


References


Bibliography

* *


External links


Information on the Amazon from Extreme Science

A photographic journey up the Amazon River from its mouth to its source

Amazon Alive: Light & Shadow documentary film about the Amazon river

Amazon River Ecosystem

Research on the influence of the Amazon River on the Atlantic Ocean at the University of Southern California
* {{Authority control Amazon basin Amazon rainforest Upper Amazon Rivers of South America International rivers of South America Rivers of Colombia Rivers of Peru Colombia–Peru border Rivers of Amapá Rivers of Amazonas (Brazilian state) Rivers of Loreto Region Rivers of Pará