Waterfall – Sudden descent of a river or stream over a vertical or very steep slope
We all know what a waterfall is, but how do they form?
It often forms where the river meets a band of softer rock after flowing over an area of more resistant material.
- Waterfalls typically form in the upper stages of a river. They occur when a band of hard rock overlies a softer rock. Falling water and rock particles erode the soft rock below the waterfall, creating a plunge pool.
- The soft rock is undercut by erosional processes such as hydraulic action and abrasion, creating a plunge pool where water and debris swirl around, eroding the rock and creating an overhang.
- The hard rock overhang above the plunge pool collapses as its weight is no longer supported.
- Erosion continues and the waterfall retreats upstream, leaving behind a gorge.