A series of long, generally straight and parallel scratches or urrows on a bedrock surface which were caused by the dragging and scraping of rock fragments that were frozen into the base of an overriding glacier; striations are usually oriented in the direction of ice movement. Glacial striations are also formed on erratics (rock fragments) transported by the ice.

lines carved into rock by overriding ice, showing the direction of glacial movement

A series of fine parallel grooves cut into the bedrock by rock fragments embedded at the base of a moving glacier, or cut into the rock fragments themselves. A good example can be seen in Lassen Volcanic National Park.

grooves or gouges cut into the bedrock by gravel and rocks carried by glacial ice and meltwater; also called glacial grooves. Striated Graywackie, Yale Glacier, Alaska. 1997. Parallel striations and bedrock fracture trends (across the left side of the image) are clearly visible in this photo. (Photo courtesy of Tom Lowell, University of Cincinnati.)

Glacial striations or glacial grooves are scratches or gouges cut into the bedrock by process of glacial abrasion during one of the Earth's Ice Ages or by mountain glaciers. Striations usually occur as multiple straight, parallel lines 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.