How does solid glacier ice move?
When ice on a slope gets thick enough it begins to deform and spread outwards under its own weight. Gravity takes over and the glacier moves downslope. The ice crystals in the glacier start to slide along internal planes, like playing cards in a deck slide over each other. At the same time the ice crystals recrystallize into new shapes, moving downslope all the time. The size (or mass) of a glacier changes as the environmental conditions change – if there is more snow to be turned into ice, the glacier will get bigger. On the other hand, in warmer periods there will be less snow, so the glacier will melt and its front end will retreat backwards. Glaciers and ice sheets stop spreading out when they meet the ocean. This is because they start ‘calving’ or breaking off into the sea forming icebergs and ice floes. As glaciers move they carve out the landscape. They scoop up and remove soil and weathered rock fragments as they travel across the surface. They flow because the weight of the ov
