❓ why
Why do some waterfalls retreat upstream over time?
GeographyWaterfalls
Quick Answer
They retreat because plunging water erodes the rock at the base and undercuts the lip. As the overhang collapses, the waterfall shifts backward.
The Full Story
At many waterfalls, the strongest erosion happens where water hits the plunge pool below the falls. That undercutting weakens the rock ledge above, especially if the top layer is harder than the layer beneath it. When the overhang breaks off, the waterfall moves upstream a little. This process can happen repeatedly for thousands of years. Niagara Falls has retreated significantly since the end of the last Ice Age, largely because of this mechanism.
Key Facts
1.Plunge-pool erosion undercuts waterfall lips
2.Collapse causes upstream retreat
3.Niagara Falls has retreated since the last Ice Age
YouTube Angle
Suggested video title for this topic:
"The hidden reason waterfalls move backward"