The wearing down of soil and bedrock by a river or stream creates a valley.

Here's how it works:

* Erosion: The river's flow carries sediment, rocks, and other debris, which act like sandpaper, grinding away at the riverbed and banks.

* Downcutting: As the river erodes downwards, it creates a channel that gets deeper and deeper.

* Lateral erosion: The river also erodes sideways, widening the channel and creating the characteristic V-shaped valley.

Over time, the valley becomes larger and deeper, shaping the landscape.