These large, rounded, sandstone boulders are along Rim Rock Drive about two miles east of the East (Grand Junction) Entrance to Colorado National Monument. Large blocks that break away from the cliff are gradually rounded as they slowly move or episodically roll down slope. Episodic soaking and drying, and freezing and thawing are powerful forces that gradually break down rocks. Finer materials are abraded away by wind, rain, and running water. |