Rock shelter

In contrast to solutional caves (karst), which are often many miles long or wide, rock shelters are almost always modest in size and extent.

Rock shelters form because a rock stratum such as sandstone that is resistant to erosion and weathering has formed a cliff or bluff, but a softer stratum, more subject to erosion and weathering, lies just below the resistant stratum, and thus undercuts the cliff.

In most humid areas, the most important factor in rockhouse formation is frost spalling, where the softer, more porous rock underneath is pushed off, tiny pieces at a time, by frost expansion from water frozen in the pores.

[1] Transhumant nomads, people who move with their livestock - often from lower permanent winter residences in the valleys to higher summer pastures - frequently build semi-permanent camps, often of rocks.

The Cumberland stitchwort (Minuartia cumberlandensis) is an endangered species of plant which is found only in rock shelters in Kentucky and Tennessee.