19.4: How Do Glaciers Move?

How Do Glaciers Move?

Glaciers flow outwards and downwards under the pressure of their own weight and the forces of gravity. Valley glaciers tend to flow down valleys, with the fastest flow rate in the upper central region of the glacier. Friction along the valley glaciers’ sides and base cause the flow rate to be much slower, whereas continental ice sheets flow outward in all directions (Figure 19.6). 

Glacial movement happens mostly through internal deformation of the ice, and by sliding over the rocks and sediments at the glacier’s bed or base. Internal deformation occurs when the weight and mass of a glacier cause it to spread out due to gravity. Sliding primarily occurs due to the presence of meltwater at the bed; more meltwater reduces friction at the base and increases the likelihood of movement. In some glaciers, an excess of meltwater can induce glacial surge events Links to an external site., where a glacier will advance quickly during a short period of time (up to 100x the normal movement). During rapid uneven movement, some glaciers will develop cracks or crevasses Links to an external site..