In this process, basal ice freezes in rock surface cracks. As the main body of the glacial ice moves material around the ice in the cracks is pulled and plucked out. The intensity of the plucking process is greatest on the lee-side of rock mounds. When combined with glacial abrasion, the action of plucking on rock mounds produces a unique asymmetrical feature known as roche moutonnee . Roche moutonnee are smooth on the side of ice advancement and steep and jagged on the opposite side.
Glaciers generally flow over the land surface along a path of least resistance.
The flow of an alpine glacier into a valley, causes the glacier to rapidly advance producing a swollen tongue of ice at the glacier's snout , known as a lobe . As the lobe moves down the valley it often encounters the lobes of other glaciers from connecting valleys. The glacier grows in size with addition of the flow of connected sub-valleys. A number of distinct erosional features can be observed in mountainous regions that have experienced the effects of glaciation. Much of this erosion is exerted on the bottoms and sides of alpine valleys that guide the flow of glaciers.