Why do some rivers form waterfalls at all?
Quick Answer
Waterfalls usually form where hard rock lies over softer rock, so the softer layer erodes faster and leaves a drop in the riverbed.
The Full Story
Waterfalls often begin where a river crosses layers of rock with different resistance to erosion. Softer rock is worn away more quickly than harder rock, creating a step or ledge. As the water plunges over the edge, it undercuts the harder cap rock and the waterfall gradually retreats upstream. Faults, glacial carving, and sudden changes in gradient can also help create a waterfall. Many famous waterfalls are geologically young because erosion keeps changing the shape of the drop.
Key Facts
YouTube Angle
Suggested video title for this topic:
"The hidden rock layers that create a waterfall"
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