General terms:
* Fissure: This is a general term for a narrow opening or crack, and it could be used for a small crack in a rocky hillside.
* Crevice: This is another general term for a crack or split, especially one that is narrow and deep.
* Fracture: This is a more specific term for a break or crack in a rock.
* Seam: This is a term used for a thin, narrow crack or gap, often between layers of rock.
More specific terms:
* Joint: This is a term for a fracture in a rock that does not involve displacement.
* Fault: This is a term for a fracture in a rock that involves displacement.
* Cleavage: This is a term for a tendency of a rock to break along specific planes.
Descriptive terms:
* Small crack: This is a straightforward description that can be used for a crack that is not very large.
* Tiny fissure: This is a more poetic way to describe a small crack.
The best word to use will depend on the specific situation and the level of detail you want to convey.
