There are more than one term for a deep narrow valley. Glens, canyons, ravines, fjords are terms you could use.
The Marianas Trench, and many other deep undersea valleys, can be found on the ocean floor.
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.
A deep valley with steep sides would be called a gorge or canyon.
Trenches, or deep sea trenches.
what do people build to cross deep rivers or valleys?
a deep, steep-sided, narrow river valley
cracks
a glen
Those deep valleys are mainly in Wales, in the southwest of Britain.
deep narrow valleys and mountains
Narrow deep valleys are sometimes called canyons. Or a small valley riginally worn away by running water and serving as a drainageway after prolonged heavy rains is called a Gully.
deep sea canyons
The Marianas Trench, and many other deep undersea valleys, can be found on the ocean floor.
You may be thinking of a fjord (or fiord), a narrow, deep inlet (generally in a coastal landscape) formed by glacial activity.
its called KARST TOPOGRAPHY
They are narrow trenches or small, narrow valleys.
Yes, a valley can be both broad and narrow. A broad valley typically has wide expanses of flat land between the surrounding mountains or hills, while a narrow valley is characterized by steep-sloped sides that are closer together. The width of a valley can vary depending on factors such as the geology, tectonic activity, and erosion processes that shaped it.