Glacial striations (glacial scratches) on Cambrian dolostone in Vermont, USA.
Glaciers are rivers of ice. Ice is a mineral (H2O). Glacial ice is a rock (technically, a metamorphic rock). Despite being solid, ice does flow under certain conditions at the Earth’s surface. Occasionally, Earth experiences Ice Ages, during which extensive ice sheets cover and move over significant portions of the Earth’s surface. As ice moves over landmasses, it erodes underlying rocks and picks up small to large pieces of debris. This debris accumulates at the base of the ice sheet and scrapes bedrock as the glacier moves, resulting in glacial scratches (glacial striations) (= thin scratch lines on rock) and glacial grooves (= large channels incised in rock).
The Cambrian dolostone outcrop seen here has linear scratches on its surface. These are glacial striations produced during the Late Pleistocene's Wisconsinan Glaciation.
Stratigraphy: Dunham Dolomite, upper Lower Cambrian
Locality: roadcut on the southern side of Route 2, just southeast of bridge over the Lamoille River, northwestern Chittenden County, northwestern Vermont, USA (44° 36' 02.54" North latitude, 73° 12' 11.33" West longitude)
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