Glaciers move due to gravity's force that is imposed on them. The massive weight of the glacier's ice explains the typically sluggish movement of glaciers.
Movement is faster at the top of a glacier than at the bottom. This discrepancy in speed of movement is because of the friction that occurs between the bottom of a glacier and the ground. When the bottom of a glacier is exceedingly cold, the movement on top may be faster relative to the flow rate of the bottom. Roughly 75 percent of all the freshwater in the world is contained within glaciers, and the sea level would increase by about 230 feet if all the ice on land in the world melted.