Flow profile is similar to a stream's, but imperceptible. Rates vary up to several meters per day. Surges are periods of extremely rapid movement. Rates may be up to 100 times the normal movement. Causes not well-known, but may be related to periods of abnormally high snowfall, or triggered by sudden changes in basal slip.
Ablation also occurs by calving where glaciers terminate along the shoreline.
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.