Figure 7. (a) Eroded bluff below parking area. Note large boulders at base, eroded from till deposit near the base of the exposure. (b) Close-up of large boulder with fractures and crescentic marks on its surface. These features are called chattermarks and are formed as the boulder slid over bedrock, cracking and chipping the boulder surface. (c) Close-up of more chattermarks from boulder in 7(b). Faint striations on the boulder are parallel to the arrow on the photo and are near perpendicular to the chattermarks. Found on bedrock surfaces, chattermarks may be used as ice-flow direction indicators. Click on images for a larger view.