Question

3.
Give reasons for each of the following:
(a) On the Earth's crust, mountains, plateaus, plains, etc. are found.
(b)The rivers are swift at their sources and slow down in their middle and old courses​

Answer 1

Many mountainswere formed as a result of Earth's tectonic plates smashing together. Plateaus ~ Many plateaus form as magma deep inside the Earth pushes toward the surface but fails to break through the crust.

It is thought that the frictional drag exerted on the water by the riverbed and banks causes lower layers of water to move more slowly and in a sinuous manner. They interfere with upper layers of water and cause them to move in a more exaggerated pattern of sinuosity.

hope it helps you.