striation

In geology, striations are scratches or grooves on a rock surface, typically a few millimeters deep and centimeters long, though some can be much larger. These marks are created by glacial abrasion, where rocks embedded in the ice are dragged across the bedrock. The long axis of a striation indicates the direction of ice movement in that specific area. To determine the regional ice flow direction, hundreds of striations are measured across a wider area, as local bedrock formations can influence the ice's path. Other small-scale glacial erosion features, like chatter marks and knob-and-tail formations, can also help pinpoint the direction of ice movement.1