Glaciers
Glaciers offer an exciting aspect for the more experienced climber. Glaciers are responsible for a lot of the shaping of valleys across the globe over the millennia.
Glaciers can actually move up to 20 metres (65 feet) per day, although a few centimetres (inches) to a few metres (10 feet) are more typical. It is important to understand that this movement does not necessarily equate to growth of the length of the glacier.
Glaciers move due to unmelted snow accumulating and compacting. The growth in the length of the glacier is determined by the air temperature at the snout of the glacier.
Glaciers have thixotropic properties. That is while they are solid they behave in some ways like a liquid. For instance a glacier flows faster in the centre than it does at the edges. This is due to the friction on the glacier from the valley floor and walls.
The friction drag from the floor of the valley is also what creates one of the most dangerous aspects of the glacier; the transverse crevice. Transverse crevasses are created as a result of the fact that the surface of the glacier is under less pressure than the rest of the glacier. This means as the glacier moves over a bulge in the valley floor large cracks appear at the base and travel upwards. By the time the crack reaches the surface it may be very small and sometimes just covered with a thin layer of snow.