General terms:
* Fissure: This is a general term for any narrow opening or crack in rock.
* Crevice: Similar to fissure, but often implies a slightly wider opening.
* Fracture: This term is more technical and can refer to any break in a rock, regardless of size.
* Joint: This term is used specifically for a fracture in rock that has no movement along it.
More specific terms:
* Hairline crack: A very small, thin crack that is barely visible.
* Stress crack: A crack that has formed due to stress in the rock, such as from erosion or tectonic movement.
* Weathering crack: A crack that has formed due to the effects of weather, such as freezing and thawing.
* Erosion crack: A crack that has formed due to the gradual wearing away of the rock by wind, water, or ice.
Other possible descriptions:
* Small opening: This is a neutral term that can be used to describe any small gap in the rock.
* Narrow gap: Similar to small opening, but emphasizes the narrowness of the crack.
* Crack in the hillside: This is a simple but effective description that gets the point across.
The best way to describe the small crack will depend on the specific situation and the information you want to convey.
