From Pathfinder #176: Lost Mammoth Valley, which isn't enabled.

Cave-in

HAZARD 4

ENVIRONMENTAL

Stealth +12 (trained)

Description The tunnel collapses, filling the passage with stone.

Disable DC 25 Survival (trained) to prop up the tunnel ceiling without triggering a collapse

AC 21; Fort +14, Ref +14

HP 46 (BT 23); Immunities critical hits, precision

Collapse

Trigger A creature moves into the unstable tunnel

Effect The tunnel collapses in a cave-in that deals 4d8+10 bludgeoning damage to the triggering creature and all creatures in area A2 (DC 21 basic Reflex). On a failed save, the triggering creature is Immobilized (Escape). This collapse fully blocks the tunnel (area A2), making it impassable.

Pathfinder #176: Lost Mammoth ValleyOGL