What do you call a deep, narrow valley with steep sides?

A canyon is a deep, narrow valley with steep sides. “Canyon” comes from the Spanish word cañon, which means “tube” or “pipe.” The movement of rivers, the processes of weathering and erosion, and tectonic activity create canyons. The most familiar type of canyon is probably the river canyon. The water pressure of a river can cut deep into a river bed. Sediments from the river bed are carried downstream, creating a deep, narrow channel.

Source: National Geographic