Glaciers live a dynamic existence, and there are several components that are unique to the way they form and sustain themselves.
Snow falls on the accumulation area , usually the highest part of the glacier.
Here, snow adds to the glacier's mass and becomes ice, building up the weight that forces it to move. Further down the glacier is the ablation area , where most of the melting and evaporation occur. Between these two areas a balance is reached, where snowfall equals snowmelt. Here, the glacier is in equilibrium . Whenever this equilibrium is disturbed, either by increased snowfall or by excessive melting, the glacier either retreats or advances at more than its normal pace.