Glacial striations on bedrock. Rocks embedded in the bottom of a massive glacier scratched the rock underneath as the glacier moved along. Even though there is no ice present today, these scratched lines are evidence that glaciers were here in the geologic past.lacial striations are parallel to the handle of the hammer. Look at how the lines all go the same direction. Click to Enlarge. About : The scratch marks on the schoolyard are formed by the process shown on top -- a broom dragged along over wet tar.