are a series of very short and fast falls.
the rapids, the river is shallow
and flowing very quickly
over rocks, boulders and stones sticking out above the water level.
When a river flows through an area of alternating bands of resistant and less resistant rocks, the less resistant rocks are eroded more quickly. Therefore, the less resistant rocks are at a lower level compared to the more resistant rocks. This results in the river falling in a series of steps along the bands of resistant rocks to form rapids.
A series of rapids is known as a cataract.
Famous Rapids in the World