Amazon River is 11 million years old already and its not too wide and releases 300 000 cubic centimeter per second so it is a mature river base to its characteristics.. :-)
The length of the Amazon River is 6,575 km or 4,086 miles. Source: S. Liu, P. Lu, D. Liu, P. Jin, W. Wang, Pinpointing the sources and measuring the lengths of the principal rivers of the world,...