In glacial geology, a chatter mark is a wedge-shaped mark (usually of a series of such marks) left by chipping of a

bedrock In geology, bedrock is solid rock that lies under loose material ( regolith) within the crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface material. An exposed portion of bed ...

surface by rock fragments carried in the base of a

glacier A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

( glacial plucking). Marks tend to be

crescent A crescent shape (, ) is a symbol or emblem used to represent the lunar phase (as it appears in the northern hemisphere) in the first quarter (the "sickle moon"), or by extension a symbol representing the Moon itself. In Hindu iconography, Hind ...

-shaped and oriented at right angles to the direction of ice movement.Marshak, Stephen, 2009, Essentials of Geology, W. W. Norton & Company, 3rd ed. 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 Lunate is a crescent or moon-shaped microlith. In the specialized terminology of lithic reduction, a lunate flake is a small, crescent-shaped lithic flake, flake removed from a stone tool during the process of pressure flaking. In the Natufian cu ...

fracture is also a downstream concave made without the removal of rock.Encyclopædia Britannica
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References

Glaciology {{glaciology-stub

See also

References