Glacier ice will move if the temperature at the base is above the pressure melting point . The temperature at the base of a glacier is a function of the thickness of the ice, friction, the input of firn , and the altitude. If these combine to give a warm glacier , and there is a gradient, the ice will move downslope.
Cold glaciers move much more slowly than warm glaciers.
It also moves when the ice crystals change into a series of flat platelets, i.e. it becomes plastic and then creeps downslope. Further movement takes place by basal slipping . All rights reserved.