A canyon or chasm
Such structure could be called a Canyon.
A valley with very steep sides is called a gorge. These landforms are typically formed by the erosion of water and can vary in size and depth. Gorges often have narrow bottoms and can be found in mountainous regions.
Basins and canyons are both valleys. A basin is a wide valley shaped like a bowl and a canyon is a very narrow valley with steep sides.
The word you are looking for is "trench." Trenches are long and narrow depressions in the seafloor characterized by very steep sides.
A 'hanging valley' is a valley which is cut across by a river flowing in a deeper valley.
It is very steep at the top and narrow but. At the bottom it isn't steep.
A plateau is a flat elevated landform with steep sides, while a canyon is a deep valley with steep sides usually carved by a river. Plateaus are generally broad and flat on the top, while canyons have narrow bottoms and high vertical walls.
A long, narrow valley between high cliffs is a canyon. Canyons within mountains, or gorges that have an opening on only one side are called box canyons. Slot canyons are very narrow canyons, often with smooth walls.
A cliff, a mountain, a ravine, a gorge, glacial valley, an arête, a cirque, a tarn. an escarpment are some possibilities.
deep: is down very low such as the ocean is deep steep: high narrow: thin wide: large or fat
shield volcanoes have gentle sides and aren't very tall
the low area between hills or mountain is called...VALLEY