A chatter mark is one or, more commonly, a series of wedge shaped marks left by chipping of a
bedrock surface by rock fragments carried in the base of a
glacier
A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as ...
(
glacial plucking
Plucking, also referred to as ''quarrying'', is a glacial phenomenon that is responsible for the weathering and erosion of pieces of bedrock, especially large "joint blocks". This occurs in a type of glacier called a "valley glacier". As a glac ...
). Marks tend to be crescent-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 which 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.
Encyclopædia Britannica
/ref>
See also
*Glacial polish
Glacial polish is a characteristic of rock surfaces where glaciers have passed over bedrock, typically granite or other hard igneous or metamorphic rock. Moving ice will carry pebbles and sand grains removed from upper levels which in turn grind ...
*Glacial striation
Glacial striations or striae are scratches or gouges cut into bedrock by glacial abrasion. These scratches and gouges were first recognized as the result of a moving glacier in the late 18th century when Swiss alpinists first associated them w ...
References
Glaciology
{{glaciology-stub