Rivers – True or false

Waterfalls typically form in the upper course of a river where hard rock overlays soft rock. The river erodes the soft rock more easily, creating a steep drop. Over time, the waterfall erodes the soft rock beneath the hard rock, forming an overhang that eventually collapses. This cycle causes the waterfall to move upstream, leaving a gorge behind.

Describe the process that occurs after the overhang collapses.

What geographical feature is left behind as waterfalls move backwards upstream?