At a Glance Size of the Amazon basin: 2.5 million square miles Length of Amazon river: 6,500 miles Quick facts: Sixteen percent of the world's river water flows through the Amazon delta. The Amazon basin is nine times the size of Texas. Fifty percent of all rainwater in the Amazon Basin returns to the atmosphere through the foliage of trees. In flood season, the Amazon rises an average of 30 feet. Only Egypt's Nile river is longer than the Amazon.

To understand the origins of Amazonia, one needs to travel back in time some 15 million years to the formation of the Andes mountains. Until that time, the Amazon river flowed west, emptying into the Pacific Ocean. But when South America collided with another tectonic plate, the Andes formed, blocking the Amazon at its Pacific end. Inland seas, now cut off from the ocean, transformed into freshwater lakes, and the environment of the Amazon basin changed radically. The Amazon's flow gradually reversed, now flowing from west to east, until roughly 10 million years ago, the river reached the Atlantic.

The Amazon River is the lifeline of Amazonia, carrying an astounding 16 percent of all the river water in the world over its 6,500 miles. A fifth of all river water discharged into the world's oceans is conveyed through the Amazon, 10 times that of the Mississippi River.