A Glacier is: ' A tongue shaped mass of ice moving slowly down a valley.' (Redfern, D and Skinner, M. 2005)
Glaciation occurs in areas of permenant snow. This is normally at high altitude, where the climate is cooler. In the northern hemisphere south facing mountains, a snow line will occur due to the south facing side recieves more insolation. As the snow line builds it becomes more compact, and with meltwater, it freezes and becomes more compact ( this can take between 20-40 years). As the air is expelled from this area of ice, the ice begins to flow downhill as a glacier.
This video, from the National Geographic Channel, shows the power of a glacier. It shows the glacier from underneath. From it you can get an understanding of how the glacier moves across the landscape.
Really nice video clip. Are you sure snow develops on the south side of mountains int eh northern hemisphere? How would you use the video to begin to enthuse students about glaciers - remembering that many of them will have spent a very limited amount of time even in the countryside, nevermind anywhere near a glacier!
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