The Amazon River 

The Amazon River of South America is one of the longest two rivers on Earth, the Nile River in Africa being the other. The Amazon has by far the greatest total flow of any river, carrying more than the Mississippi, Nile, and Yangtze rivers combined. It also has the largest drainage area of any river system. It may be correctly stated that the Nile is the longest river, while the Amazon is the strongest. 

The quantity of fresh water released to the Atlantic Ocean is enormous: 184,000 m³ per second (6.5 million ft³/s) 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. 

The main river (which is usually between one and six miles wide) is navigable for large ocean steamers to Manaus. Smaller ocean vessels of 3,000 tons[1] and 5.5 m (18 ft) draft[2] can reach as far as Iquitos, 3,700 km (2,300 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 7,200 km (4,800 mi) through the interior of Peru and across Brazil, it enters the Atlantic Ocean at the equator. 

Source and Upper Reaches 

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 (100 miles) N.N.E. of Lima. The mountain was first suggested as the source in 1971 but this was not confirmed until 2001. The stream from Nevado Mismi flows into Lake Lauricocha and then the Apurímac River. The Apurímac is a tributary of the Ucayali, which joins the Marañón to form the Amazon proper. 

Below its confluence with the Huallaga, the river leaves Andean terrain and is instead surrounded by flood plain. From this point to the Ucayali, some 2,400 km (1,500 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. 

Flooding 

Seasonal rains give rise to extensive floods along the course of the Amazon and its tributaries. 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 abundance of water in the Amazon basin is due to the fact that much of this lies in the region below the Inter-tropical convergence zone, where rainfall is at a maximum. Also, the basin lies in the Trade Wind zone, where moisture from the Atlantic is pushed westwards, and eventually forced to rise over the Andes, the second tallest mountain range on Earth, where the moist air cools and precipitates water. This combination creates more rainfall over a large river basin than anywhere else on the planet. 

In the rainy season, the Amazon inundates the country throughout its course to the extent of several hundred thousand square miles, covering the flood plain, called vargem. The flood-levels are, in some places, from 12 to 15 m (40 to 50 ft) higher than levels during the dry season. During the flood, the level at Iquitos is 6 m (20 ft); at Teffe, it is 15 m (45 ft); near Obidos, 11 m (35 ft); and at Para, 4 m (12 ft), above the low-water extreme seen during the dry season. 

Towards the Sea 

The breadth of the Amazon in some places is as much as 6 to 10 km (4 to 6 mi) from one bank to the other. At some points, for long distances, the river divides into two main streams with inland and lateral channels, all connected by a complicated system of natural canals, cutting the low, flat igapo lands, which are never more than 5 m (15 ft) above low river, into almost numberless islands. 

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

From the village of Canaria at the great bend of the Amazon to the Negro 1,000 km (600 mi) downstream, only very low land is found, resembling that at the mouth of the river. Vast areas of land in this region are submerged at high water, above which only the upper part of the trees of the sombre forests appear. Near the mouth of the Rio Negro to Serpa, nearly opposite the river Madeira, the banks of the Amazon are low, until approaching Manaus, they rise to become rolling hills. At Óbidos, a bluff 17 m (56 ft) above the river is backed by low hills. The lower Amazon seems to have once been a gulf of the Atlantic Ocean, the waters of which washed the cliffs near Óbidos. 

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

In the lower reaches of the river, the north bank consists of a series of steep, table-topped hills extending for about 240 km (150 mi) from opposite the mouth of the Xingu as far as Monte Alegre. These hills are cut down to a kind of terrace, which lies between them and the river. 

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

Mouth of the River 

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 Marajo, an island about the size of Denmark lying in the mouth of the Amazon. 

Tidal Bore 

Following the coast, a little to the north of Cabo do Norte, and for 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. 

European Exploration 

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

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

Name 

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

The name Amazon arises from a battle that 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.