Where is the mature and senile stage of the river Amazon?

Question

Please do this quickly!!!!!!!!!!

Answer 1

"Although the following classes are a useful simplified way to visualize rivers, it is important to recognize there are other factors at work here. Gradient is controlled largely by tectonics, but discharge is controlled largely by climate and sediment load is controlled by various factors including climate, geology in the headwaters, and the stream gradient.
Youthful river - a river with a steep gradient that has very few tributaries and flows quickly. Its channels erode deeper rather than wider. (Ex: Brazos River, Trinity River, Ebro River);
Mature river - a river with a gradient that is less steep than those of youthful rivers and flows more slowly than youthful rivers. A mature river is fed by many tributaries and has more discharge than a youthful river. Its channels erode wider rather than deeper. (Ex: Mississippi River, Ohio River, River Thames);
Old river - a river with a low gradient and low erosive energy. Old rivers are characterized by flood plains. (Ex: Tigris River, Euphrates River, Indus River, Nile River)."

As a high school earth science teacher, I agree with the above simple classification of river systems.
I would say that some of the Amazons' Andean sources are young rivers; some of the Amazon basin's rivers which are tributaries of the Amazon itself are mature rivers; and the Amazon itself is an old river.
The textbook I use ["Concepts and Challenges" by Bernstein, Schachter, Winkler & Wolfe and published by Globe Fearon] says the Mississippi is an old river (and so disagrees with Wiki's article, which calls it a mature river).