Question

Why do rapids form in the upper course of a river?​

Answer 1

Rapids form when there is vertical bedding which is when alternate bands of hard and soft rock cross the channel. Differential erosion will occur as soft rock is more easily eroded than hard rock. This makes the riverbed uneven and a river’s flow becomes turbulent leading to white water sections typical of rapids.

Answer 2

As the river erodes the landscape in the upper course, it winds and bends to avoid areas of hard rock. This creates interlocking spurs, which look a bit like the interlocking parts of a zip. When a river runs over alternating layers of hard and soft rock, rapids and waterfalls may form.