Landforms Created By Rivers Formation of a Waterfall

Landforms Created By Rivers Formation of a Waterfall and Gorge

Formation of a Waterfall A waterfall often occurs when a river flows from one rock type onto another. For example, if the river flows from the harder rock and onto softer rocks because of the vertical movement of rocks along a fault line in the past. 2. Hard, resistant rock The river erodes vertically into the river bed. Vertical erosion happens at a faster rate in the softer rocks than in the harder rocks. Hard, resistant rock Relative movement of rocks along the fault Soft, less resistant rock

Formation of a Waterfall Over a long period of time, thisriver difference The erodes in the rate of erosion vertically into the river creates a step in the bed. Vertical erosion river bed and waterfall happens at aafaster rate formed. in the issofter rocks than in the harder rocks. 2. Hard, resistant rock Soft, less resistant rock Hard, resistant rock

Formation of a Waterfall As the river falls over the waterfall the water has a lot of energy. Some of this energy causes erosion by hydraulic action. If the river carries a lot of sediment (or load) it can use this to erode the river bed through the process of abrasion. These processes of erosion create a plunge pool at the base of the waterfall. 2. Hard, resistant rock Soft, less resistant rock Hard, resistant rock

Formation of a Waterfall A new overhang will form here Overhang Hard, resistant rock The erosion of the softer rock undercuts the harder rock which collapses. Soft, less resistant rock Plunge pool Hard, resistant rock

Formation of a Waterfall Original position of waterfall Over a long period of time, the position of the waterfall moves upstream in a process called retreat. New position of waterfall Hard, resistant rock The retreat of the waterfall causes a gorge to be formed. Soft, less resistant rock Hard, resistant rock

Formation of a Gorge Over time the waterfall continues to move upstream enlarging the gorge Present day waterfall Gorge formed by retreat of waterfall Direction of flow Original site of waterfall

Landforms Created By Rivers Formation of a Waterfall and Gorge