The term used for narrow deep valleys is "ravine."
a glen
a deep, steep-sided, narrow river valley
A zawn is a deep and narrow inlet in the British Isles, cut by erosion into sea-cliffs, with steep or vertical side-walls.
Ravines.
Ravine
deep narrow valleys and mountains
Ravine, gorge, canyon.
There are more than one term for a deep narrow valley. Glens, canyons, ravines, fjords are terms you could use.
The deep narrow valleys on the Moon are called rilles. These are long, winding depressions that can stretch for many kilometers across the lunar surface. Rilles are thought to have been formed by a combination of ancient volcanic activity and tectonic forces.
A narrow valley is a V-shaped valley, or river valley. A narrow valley has steep sloped sides that look like the letter V. They are formed by a strong stream.
Lake morar in Scotland its the deepest at 310 metres deep