Here's why:

* Glaciers are powerful agents of erosion. Their immense weight and slow, grinding movement carve out valleys, create U-shaped valleys, and sculpt mountains.

* Glacial scour refers specifically to the process of a glacier scraping and eroding the bedrock beneath it. This happens due to the glacier's weight, the embedded rock fragments within the ice (called glacial debris), and the abrasive action of the ice itself.

Let me know if you have any other questions!