However, average rates of movement are usually less than 1 meter per day. Cold glaciers tend to move very slowly because there is no basal sliding. Movement in these glaciers takes place mainly due to internal slippage of the ice over the ground. Glacier Mass Balance Scientists often view glaciers as systems that are influenced by a number of inputs and outputs . The main inputs to the glacial system are water, in the form of snow , and eroded sediments that are picked up by the moving ice.
Water leaves the glacial system when ice is converted into water or vapor.
Sediment is deposited at the base of the glacier as till and at its terminal end as moraines or materials reworked by glaciofluvial processes. We can also use a systems approach to help us understand why glaciers expand and shrink, and advance and retreat . This type of modeling is referred to as glacier mass balance . The zone of accumulation occurs in the upper reaches of the glacier where yearly additions of snow exceed losses due to melting , evaporation , and sublimation . The surface of this zone is covered by snow throughout the year.