In the upper course of of the River Severn, where vertical (downwards) erosion is dominant, many small waterfalls can be seen. Waterfalls usually occur where a band of hard rock lies next to soft rock.
Soft rock is being eroded.
Pooh wonders if this is the first stage of a gorge forming?
The following falls on the Severn are just about a mile downstream from the source. The force of the water has shaped the triangular rock below.
Pooh wonders whether, one day, the force of the water will erode the rock underneath.
As the river passes over the hard rock, the soft rock below is eroded (worn away) more quickly than the hard rock leaving the hard rock elevated above the stream bed below. The drop gets steeper as the river erodes the soft rock beneath.
A plunge pool forms at the base of the waterfall.
A waterfall is a
cascade of water over a hard rock step in the upper course of a river
A plunge pool is
deep pool beneath a waterfall.
is the wearing away of the bottom and sides of the rivers by the force of the water, and material carried by the water.
This process involves the force of water against the riverbed and banks.