Human: Produce a detailed written description of a dreary wilderness ravine with gravel, a ravine, and a leaning wall. Assistant: 
Shallow grooves worn by years of running water undulate across the floor of the ravine. The depressions form catch-basins for rubble fallen from the rock walls, filling with gravel and other debris to make for hazardous footing. Overhead, the south wall of the ravine leans in at an acute angle, making it impossible to climb.