A canyon or chasm
small rocky stones
Such structure could be called a Canyon.
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.
A V shaped valley, over time the river erodes downwards causing a channel, then the rocks at the sides collapse in because they have nothing supporting them causing a valley with steep sides
A 'hanging valley' is a valley which is cut across by a river flowing in a deeper valley.
Trench.
It is very steep at the top and narrow but. At the bottom it isn't steep.
A deep narrow valley with steep sides that sometimes has a stream or river flowing through it is called a gorge. Gorges are typically formed by the erosive action of flowing water over a long period of time, creating a dramatic and picturesque landscape.
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
shield volcanoes have gentle sides and aren't very tall