How can glacial grooves determine the direction a glacier has moved?

Glacial grooves are striations or scratches left on rock surfaces as glaciers move over them. The orientation and alignment of these grooves indicate the direction of the glacier's flow, as they are created by the movement of debris embedded in the glacier's base. By analyzing the pattern and angle of the grooves, geologists can determine the glacier's path and the dynamics of its movement during its advance and retreat.