definitions
As the river bed crosses on to soft rock from hard rock it is eroded at a faster rate and a step is created.
As the water ’falls’, hydraulic action continues to erode the rock underneath the hard rock as it splashes against it.
As the soft rock is further eroded the overhang becomes too heavy and the rock collapses causing the position of the waterfall to retreat upstream.
A plunge pool is created underneath the waterfall due to the sheer force of the water hitting the river bed and the abrasion caused by the rocks from the overhang being moved by the water.
erosion
river cliff
deeper water
faster flow
deposition
slow flow
slip off slope
shallow water