A "fissure" is a crack or break in something. You might use the word "fissure' to describe a steep-sided canyon, something that looks like a crack in the mountain. You would not use "fissure" to describe the mountain itself.
DUNE
It would be more detailed. It would let people know how steep a certain hill/ mountain is.
A mountain is an elevated area of land, higher than a hill, with sloping sides, a plateau is a fairly flat area above surrounding land and a plain is a large, flat area of land usually without trees.
steep snow-covered hill, and a trigger
A steep inclined plane is worse than a more flat inclined plane.
A Gorge. Your Welcome!
sugar loaf
Caldera/ crater.
An arete is a mountain ridge that is steep sided and narrow along the ridge.
In steep sided, snow covered mountain valleys.
Gorge
a steep-sided, pyramid-shaped peak produced by the intersection of several cirques
A Butte
This is called a stratovolcano or a composite volcano.
A steep-sided tower of rock is a butte
That is a fjord.
are the tops of some mid-ocean ridges split by a steep-sided valley