Chatter mark

For chatter marks made in machining, see Chatter (machining).

In glacial geology, a chatter mark is a wedge-shaped mark (usually of a series of such marks) left by chipping of a bedrock surface by rock fragments carried in the base of a glacier (glacial plucking). Marks tend to be crescent-shaped and oriented at right angles to the direction of ice movement.^[1][2]

Chatter marks on sandstone south of Lac Beauchamp, in Gatineau, Quebec, Canada

There are three different types of chatter marks. The crescentic gouge is an upstream concave that is made by the removal of a piece of rock. The crescentic fracture is a downstream concave that is also made by the removal of rock. The lunate fracture is also a downstream concave made without the removal of rock.^[3]

See also

• Glacial polish
• Glacial striation