Glacial striations or glacial grooves are scratches or also gouges cut into bedrock by process of glacial abrasion. Glacial striations usually occur as multiple straight, parallel grooves representing the movement of the sediment-loaded base of the glacier. Large amounts of coarse gravel and boulders carried along underneath the glacier provide the abrasive power to cut the grooves, and finer sediments also in the base of the moving glacier further scour and polish the bedrock.
Most glacial striations were exposed by the retreat of glaciers since the Last Glacial Maximum or the more recent Little Ice Age. As well as indicating the direction of flow of the glacial ice, the depth and extent of weathering of the gouges may be used to estimate the duration of post-glacier exposure of the rock.
An extreme example of glacial striations can be found at the Glacial Grooves at Kelleys Island, Ohio (a National Natural Landmark), the most impressive of which is 400 feet (120 m) long, 35 feet (11 m) wide, and up to 10 feet (3.0 m) deep. These grooves cut into the Columbus Limestone.
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