Glacial scratches and striations (IMAGE) Geological Society of America Caption Glacial scratches and striations carved by direct glacial action onto the vertical walls of the U-shaped valleys seen above. At the background, reddish sedimentary rocks lie upon these vertical straited walls. Credit Credit: Pierre Dietrich. Usage Restrictions Credit must be given to the creator. Only noncommercial uses of the work are permitted. License CC BY-NC Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.