Rubble (Scenery)

Rubble is an atmospheric scenery that comes in the form of piles of dust and stones. Rubble appears naturally in caves as they are gradually dislodged from the cave ceiling, but will also appear when mining. Rubble gets in the way of growing mushrooms and roots, assembling constructs, and your dwarves must sweep it away before performing such jobs.

It is a planned feature for spawning rubble to be the first sign of a cave-in.