The budget of a glacier is equal to the accumulation minus the ablation. The terminus of a glacier will advance if the budget is positive and recede if it is negative. A receding glacier may reach a new state of equilibrium if the recession primarily reduces the zone of ablation. Even in a receding glacier, the ice within the glacier continues to move forward, although not as fast. Glacial Erosion Moving ice scrapes, scours, and tears rock from the floor and walls of its valley.
Glacial ice has great competency.
Plucking - the entraining of fractured bedrock into the ice along its margins. Abrasion - the scraping produced by the ice and its load of rock fragments on the adjoining rock masses. Straighter valleys than those cut by rivers. Hanging valleys - less deeply cut side valleys of spur glaciers. Cirques - the bowl shaped depression with precipitous walls at the head of a glacier.