The base of the glacier melted into the underlying rocks due to the heat caused by friction. Then the meltwater froze again, and as the glacier moved on, it plucked chunks of rock out of the ground.
2
Plucked rocks became embedded in the base of the glacier. As the glacier moved, the rocks abraded the rock surface they passed over.
A glaciated valley was originally a V-shaped river valley that became straightened and deepened by a glacier filling it, which changed it to look more U-shaped.
BEFORE THE ICE AGE DURING AFTER
Plucking + Abrasion
Flat valley floor
Very steep sides
Examples: Glendalough, Co. Wicklow, and Doolough Valley, Co. Mayo.
U-shaped valley, Glendalough
What evidence of glaciation can you identify in this image?