Explain the processes involved in the formation of a waterfallWatch
-A waterfall is an erosional landform that occurs upstream when there is a horizontal layer of hard rock on top of a layer of softer rock.
-Erosional processes such as hydraulic action (the force of the river compressing air in rock cracks and consequently breaking bits off) occur as the river flows downstream.
-Differential erosion takes place, because of the soft rock being less resistant, and the hard rock is left overhanging over time.
-The hard band of rock can no longer support itself and breaks off, adding more material for erosion in the plunge pool at the base of the waterfall.
-This process continues upstream, forming a steep sided gorge as it goes.
A fairly solid response to the question. I would add that as the soft band of rock is eroded away at the riverbed, a notch forms and this increases the velocity of the river (by decreasing friction), thereby exacerbating erosion vertically and creating a steep fall.