❓ why
Why do waterfalls usually form where hard and soft rock meet?
NatureWaterfalls
Quick Answer
Waterfalls often form where a resistant layer of rock sits above softer rock. The softer layer erodes faster, leaving a ledge that the water tumbles over.
The Full Story
A waterfall commonly develops when a river crosses rock layers with different resistance to erosion. Harder rock, such as basalt or sandstone, can protect the softer rock beneath it. As the softer layer erodes away, an overhang forms and eventually collapses. This process makes the waterfall retreat upstream over time. Niagara Falls is a famous example, and its position has migrated upstream for thousands of years as erosion continues.
Key Facts
1.Differential erosion creates many waterfalls
2.Niagara Falls has retreated upstream over time
3.Hard cap rock can protect softer rock below
YouTube Angle
Suggested video title for this topic:
"Why rivers suddenly drop off a cliff"