Amazon River

The Amazon River (occasionally River Amazon; Spanish: Río Amazonas, Portuguese: Rio Amazonas) of South America is one of the two longest rivers on Earth, the other being the Nile in Africa. The Amazon has by far the greatest total flow of any river, carrying more than the Mississippi, Nile, and Yangtze rivers combined. Its drainage area, called the Amazon Basin, is the largest of any river system. The Amazon could be considered the "strongest" (largest volume of water per second).

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.

Related Topics:
Channel - Canal

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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).

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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.

Related Topics:
Canaria - Gulf - Atlantic Ocean

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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.

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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.

Related Topics:
Hill - Monte Alegre - Terrace

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

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