Most glacial valleys were originally formed by stream erosion and then widened as the glacier eroded the valley walls. The main characteristic of glacial valleys (or troughs) is the U-shaped cross section which differs greatly from the V-shaped valleys formed by stream erosion. The glacial valleys are usually steeper at the valley head and contain a cirque. The longitudinal profile sometimes reveals "steps" down the valley indicating rock (possibly less jointed or much harder) that resisted abrasion. These valleys often contain little soil and the barren rock surfaces sometimes contain scratches and striations due to the abrasion of the ice.
Images
valley profile Leet, L. D., S. Judson, and M. E. Kauffman.
Physical Geology.
Prentice-Hall, Inc., Englewoods Cliff, New Jersey, 1982.
