The
Amazon River or River Amazon (Spanish: RÃo Amazonas; Portuguese: Rio Amazonas) of South America is the most voluminous river on earth, having a greater total flow than the next six largest rivers combined. Accordingly, it is sometimes known as The River Sea. The Amazon is also generally regarded by most geographic authorities as being the second longest river on Earth (the longest being the Nile in Africa).
The drainage area of the Amazon in Brazil, called the Amazon Basin, is the largest of any river system. If the Basin were an independent country, it would be the world's seventh largest, having more than twice the area of India (which actually does rank seventh).
The quantity of fresh water released by the Amazon to the Atlantic Ocean is enormous: up to 300,000 m³ per second in the rainy season. Indeed, the Amazon is responsible for a fifth of the total volume of fresh water entering the oceans worldwide. It is said that offshore of the mouth of the Amazon potable water can be drawn from the ocean while still out of sight of the coastline, and the salinity of the ocean is notably lower a hundred miles out to sea. This mixture of fresh and salt water is known as
brackish water.
This huge amount of water is responsible for the fact that the Amazon has no clouds above its channel near its mouth, as it is very easy to see in the satellite image. The reason for this is that satellite images are almost always taken during morning hours, when there are fewer clouds. This time of the day is also when water is colder and land is beginning to be much warmer: above big rivers (the Orinoco and Caura rivers in Venezuela and many more have the same characteristic), cold waters create a high pressure air mass which make rivers easy to see through clouds. On the contrary, during afternoons, clouds cover most river channels.
The main river (which is usually between one and six miles wide) is navigable for large ocean steamers to Manaus, 1,500 km (more than 900 miles) upriver from the mouth. Smaller ocean vessels of 3,000 tons[1] and 5.5 m (18 ft) draft can reach as far as Iquitos, 3,600 km (2,250 miles) from the sea. Smaller riverboats can reach 780 km (486 mi) higher as far as Achual Point. Beyond that, small boats frequently ascend to the Pongo de Manseriche, just above Achual Point.
The Amazon drains an area of some 6,915,000km (2,722,000 mile), or some 40 percent of South America. It gathers its waters from 5 degrees north latitude to 20 degrees south latitude. Its most remote sources are found on the inter-Andean plateau, just a short distance from the Pacific Ocean; and, after a course of about 6,400 km (4,000 mi) through the interior of Peru and across Brazil, it enters the Atlantic Ocean at the equator.
The Amazon has changed its drainage several times, from westward in the early Cenozoic to its present eastward locomotion following the uplift of the Andes.
