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Conservative estimates put the Amazon at 4,000 miles in length,
and some experts think it is closer to 4,300 miles, which would
surpass the Nile. The river’s rainforested drainage basin sprawls
across nearly 2.7 million square miles, an area that is almost as big
as Australia and twice the size of the planet’s next largest drainage
basin—that of the Congo, in central Africa. During the rainy sea-
son, the Amazon and its tributaries swell, solid ground vanishing
in the lowlands as the river floods and nourishes the forest floor.
The weight of the flooding river at low altitudes compresses the
Earth’s crust by about three inches. Measuring the river’s flowabout 11 million years ago began to push the water eastward,
eventually draining the lake and forming the river we know
today. The expanse of that ancient freshwater lake is now an
ecological palimpsest, a zone dominated by the world’s largest
tropical rainforest, home to the richest diversity of plants and
animals on Earth.
BY NEARLY ANY METRIC, the size of the Amazon is difficult to
fathom. Incredibly, there is still debate over the length of the
river, and over which river is longer, the Amazon or the Nile.