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river erosion
Question | Answer |
---|---|
what are waterfalls? | waterfalls are vertical interruptions in the rivers profile that occur due to vertical erosion in the youthful stage |
examples | torc waterfall powerscort waterfall |
How do waterfalls occur | occur where a band of hard rock lies upstream of soft rocks |
how do they erode rock | river has a high velocity and therefore large erosive power which vertically erodes the river bed |
what is differential erosion | the soft rock is eroded faster than the hard rock. |
how does hydraulic action erode the water bed | The swirling water carves out out hollows across the river bed through hydraulic action |
whats abrasion | broken rocks become trapped in hollows causing them to deepen and widen. |
The rate of hydraulic action is increased. Its impact shatters the rock at the base creating a plunge pool | |
hydraulic action and abrasion widen the plunge pool causing it to erode backwards this is known as undercutting | |
what is an overhang | as undercutting continues the layer of hard rock is left elevated |
eventually the overhang becomes unstable and collapses which increases the rate of abrasion | |
how is a gorge created | as undercutting and collapsing continues the waterfall gradually retreats upstream which is known as headward erosion which creates steep sided valleys |