The Amazon once menstruate in the polar direction , from due east to west . Reversing the focal point of the Earth ’s largest river is no trivial matter , and geologists have pondered the cause for some time . InEarth and Planetary Science LettersThe University of Sao Paulo ’s Dr Victor Sacek has attest that nothing more than erosion is needed to explicate this enormous geological fault .
With the mighty Andes at the westerly remnant of the continent it seems logical that South America ’s rivers menstruate east . While the Amazondischarges five time as much wateras any other river on the planet , The Orinoco and the Rio de la Plata hunt the same elbow room , each dwarfing any river in North America or Europe in the process .
However , until 10 million years ago , most of what is now the Amazon drainage basin was drained bya river that flowed westinto a giant lake that lie at the infantry of the northern Andes . From there the water menstruate northward to the Caribbean Sea . Since the Isthmus of Panama had yet to form , this water was then swing west into the Pacific .
To cant an entire continent seems such a vast endeavor that geologistshad speculatedchanges in convection within the Earth ’s curtain , perhaps resulting from the break - up of Africa and South America , must have driven this .
Sacek , on the other hand , shows that the rise of the Andes as the South American platerode over the Nazca Platecan explain the process on the appropriate timescale . Sacek included in his model the fact that as the mountains rose they intercepted more rain - acquit clouds , which in turn spark more erosion .
At first the Andes rise produce a till to the E , which became the paleolake into which the westwards - flowing Amazon emptied . With time , however , this sinking slow and erosion accelerate , replacing the lake with a series of wetlands known as the Pebas . The huge Pebas marshlands would have been an ecosystem like nothing we see today , but eventually sediment aggregation raised the region to the point where the rain in the field was crowd back the other way .
The good example successfully matches the observance that sediment deposited at the Amazon ’s mouth has increase over the period of its eastward flow . At first , when the Amazon ’s source were comparatively flat , much of the deposit was knock down part elbow room to its back talk , only being remobilized eons later .
Sacek admit however , that his model “ Fails to fully procreate the spacial and temporal development of the Pebas system as observed in geological information ” and says further work is require .
H / TScience
