In carpentry, chattermarks are the transverse gouging of a plank, caused when a smoothing tool—a plane or a sander, say—is not properly aligned, adjusted, or employed. In glacial geology, chatter-marks are small curved scars in a brittle bedrock surface. They result from the vibrational chipping action of rock fragments in the base of a glacier. Each mark is roughly at right angles to the direction in which the glacier was moving, rather like rumble strips on a highway. The mark is usually crescent-shaped. Chattermarks should be distinguished from glacial striations, which are thin, sharply incised furrows that run parallel to each other and to the direction in which the glacier traveled; they result from the scouring action of rocks embedded in the glacier’s base.