Glacial grooves, East Sister Island, Lake Erie, Ontario, Canada. The glacial grooves shown here are roughly 385 million years old, and were created from the gouging action of ice flowing in the Lake Erie basin. Source: Natural Resources Canada / R. N. McNeely.
A glacial groove is a deep, wide, usually straight furrow cut in bedrock. It is caused by the abrasive action of large rock fragments dragged along the base of a moving glacier. The grooves are larger and deeper than glacial striations, ranging in size from a deep scratch to a glacial valley.