Mass balance is important in understanding glacial dynamics and the operation of glaciers as systems

Formation of Glaciers
– Snow accumulates and compacts into an upland nivation hollow.
– Over 3-4yrs, water is squeezed out of the ice, percolates down and refreezes onto the bottom of the glacier (firn/nevé).
– Gravity and the weight of the ice above will gradually further compact the ice until it becomes glacier ice.
– The glacier will then begin to flow over the lip as a result of gravity and the gradient of the underlying slope.

The Glacier System
Accumulation – the gaining of glacier mass.
Ablation – the losing of glacier mass.
Glacier Mass Balance – the net difference between accumulation and ablation over the course of one year.
Positive Mass Balance – where accumulation exceeds ablation, i.e. there is net accumulation.
Negative Mass Balance – where ablation exceed accumulation, i.e. there is net ablation.
Equilibrium – where ablation is equal to accumulation.
Line of Equilibrium – the theoretical point on a glacier where accumulation is equal to ablation. This point moves according to seasonal and longer-term changes in the climate.
Zone of accumulation – the area of the glacier upslope of the line of equilibrium, where there is net accumulation.
Zone of ablation – the area of the glacier downslope of the line of equilibrium, where there is net ablation.