Ice covers one tenth of the Earth's surface. Glaciers are formed from delicate crystals of ice, yet they can be so heavy they dent the Earth's surface. They move faster during the summer as the meltwater beneath them acts as a lubricant, enabling the heavy ice to slide more easily over the bedrock. Some glaciers are retreating as a result of global warming. Their ice records tell us about climate change over time. Ordnance Survey mapping © Crown Copyright. With thanks to 'Luc Moreau'.
In preparation for the clip, the students could be given a graph showing the variation in glacier velocity over a year and a simple side view of the glacier. As they watch, they need to identify information which will help them explain the difference between the glacier in summer and in winter. After watching the clip, they should annotate their graph/diagram to explain the variation.