Final answer:
Scratches on rocks caused by the movement of glaciers are known as striations, which are formed by debris embedded in the ice scraping the bedrock.
Step-by-step explanation:
Scratches imparted on rocks by glaciers are called striations. These scratches occur when glaciers, carrying debris of various sizes, move across the bedrock. The embedded debris in the ice grinds against the rock surface, leaving behind long, parallel scratches.
As glaciers move and flow, similar to very slow rivers, they scrape the surface beneath them. The process is akin to sandpaper being dragged across wood, where the debris in the glacier acts as the abrasive particles in the sandpaper. Notably, these glacier striations can be used to interpret the direction of a glacier's movement, serving as indicators of what are known as paleocurrents. This observation was crucial in developing our understanding of ancient glacial movements across the Earth's surface.