Located: Nant Ffrancon Valley, Wales
When The glacier moves downhill through a V-shaped valley it abrades the sides and base using frost-shattered material, picked up via plucking. This turns the V-shaped into a U-shaped valley which is flat-bottomed and steep-sided. This also causes the formation truncated spurs.
Where the glacier cuts through another higher V-shaped valley it can lead to the formation of a hanging valley. If the V-shaped valley contains a river then a waterfall is additionally formed as the river is cut off mid-stream.
Ribbon Lakes
Located: Llyn Ogwen, Windermere, Wales
It is parallel sided and can only occur when there is a change in geology.
