Into the Depths of the Amazon
The River
Of course, no trip to the Amazon River Basin would be complete without the Amazon River
itself. Though not the longest in the world, it does flow for almost 2,000 miles and does
contain the largest volume of water.
History
The Amazon started to form over 200 million years ago when its highlands were formed on
Gondwanaland, daughter of Pangea. The Amazon River, newly formed, flowed west to the
Pacific as there was no barrier to stop it. 140 million years ago, Gondwanaland
split apart and South America was left adrift. When the South American plate collided into
the Nazca plate, the impact crushed the young rocks of Southern America to form the Andes.
This fresh mountain range blocked off the former mouth of the Amazon River, creating a
huge fresh water lake.
Over the next 50 million years, the continent began to tilt. Eventually, this caused
the freshwater lake to burst through its stony barriers and form the Amazon River Basin.
The Journey to the Atlantic
The Amazon’s headwaters begin in the Andes amid the remains of the ancient lake.
Through a series of tributaries, the water pours into the Amazon River. The powerful, fast
moving portion of the Amazon, falling 16,000 ft within its first 620 miles, soon gives way
to a meandering stream that wanders across the flat basin.
The varied terrain allows for three basic types of water that float along the path:
Whitewater, clearwater, and blackwater.
The whitewater rivers are a dirty, yellowish color. The color is caused by large
accumulations of silt and other sediment in the water. The water comes from the Andes,
washing off the soil nutrients from the young rocks.
Clearwater rivers are a blue-green color and they carry little sediment. The highlands
that the clearwater rivers flow from are made of hard rock and not easily eroded.
Finally, the blackwater rivers are the color of dark tea. They have little sediment
like the clearwater rivers because the rocks they wash over are so old that they have been
leached of minerals.
The different types of river meet at various sections along the way, making interesting
patterns as they pass by each other, side by side, with different colors. While it may
seem like a small difference to us, it makes a large difference to the wildlife which are
more often found in whitewater rivers that are full of sediment.
The Amazon continues
As the river meanders away from the Andes, it looses some of the sediment-rich water, dropping it on the “vareza”, the Amazonian Flood Plain. It is here that the rich nutrients from the Andes range go into the ground to create immensely fertile soil, soil more fertile than in any other area of the Amazon. After the long meanders by the “vareza”, the Amazon finally empties out to the Atlantic with a mouth over 205 miles across. It pushes fresh water out into the sea for 155 miles, going around a island in the center of the mouth named Marajo which is about the size of Switzerland. With the speed of 10 million liters per second, the Amazon once again proves its might.