What are the components of a glacier?
This hanging glacier above Lyman
Lake in Washington State may look simply like a mass of snow, but the crevasses
are evidence that it really is a glacier.
—United States Forest Service photograph/NSIDC
Photo: Barnard Glacier shows several medial
moraines. In this case, the widest medial moraines occur where additional
glaciers flow into Barnard Glacier.
—Austin S. Post photograph/NSIDC
Glaciers live a dynamic existence. Several elements contribute to glacier formation and growth. Snow falls in the accumulation area, usually the part of the glacier with the highest elevation, adding to the glacier's mass. As the snow slowly accumulates and turns to ice, the glacier increases in weight, forcing glacial movement. 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.
Several visible features are common to most glaciers. At locations where a glacier flows rapidly, giant cracks called crevasses are created, which may make travel across a glacier treacherous. Underneath the glacier, where glacier ice meets the ground, large amounts of rock and soil are ground up by the tremendous weight of the glacier.
Other common glacial features are moraines, created when the glacier pushes or carries along rocky debris as it moves. These long, dark bands of debris are visible on top and along the edges of glaciers. Medial moraines run down the middle of a glacier, lateral moraines along the sides, and terminal moraines are found at the terminus, or snout, of a glacier. Sometimes one glacier flows into another, creating combined wider morraines as shown in the photo to the left.