Glacial ice advances, then retreats.
Glaciers grow and shrink in response to changing climate.
Not all glaciers move slowly. For example, surging glaciers experience dramatic increases in flow rate, sometimes traveling as much as ten to one hundred times faster than the normal rate of movement. By monitoring glaciers over time and around the world, researchers construct valuable records of glacial activity and their response to climate variation. By comparing contemporary observations with historical and environmental records, such as agricultural records, pre-historic temperature or climate profiles, glaciologists acquire and provide an enhanced understanding of global processes and change.