Outline the main inputs and outputs of the Athabasca glacier
There are two main types of input for the Athabasca Glacier. One is in the form of snow and the other is due to avalanches.
The temperature can drop to as low as -40 degrees. The all year-round snow allows it to settle on the glacier in a laminar way. The snow originates from hot air on the Pacific Ocean being forced up to the top of the much colder Rockies and hence condensing in the form of snow and sometimes rain in the summer months. There is an average snowfall of 7 meters per year. The old snow is compacted due to the sufficient weight of the overlying newer snow.
Avalanches are more common in the zone of accumulation. This is because it is the area where the snow is least stable. This source also has a secondary input. This is sediment. The load can vary in size; anything from large boulders that have been plucked from the Mount Athabasca Corrie to even the smallest of sediment particles from all types of moraine.
Melt water makes up the majority of the Athabasca Glacier’s outputs. It can form pools under and on top of the glacier and can from glacial lakes at the snout of the glacier. These pools have the tell tale blue tint due to the very fine rock flour that is as a result of englacial attrition.
Finally, a very small percentage of the Glacier’s output is formed by the process of sublimation. This is when ice (solid form) changes state straight into water vapour (gaseous form.)
Explain where the glacier is moving fastest and why
Variation in velocity is due to different amounts of friction. The area with the least friction is in the middle of the glacier. From this we can deduce that this is also the fastest part of the glacier. In this are friction is very small because the glacier is not actually touching but itself. While at the sides and the bottom of the glacier the ice is in constant contact with the valley. The glacier is also relatively fast at the top. The weight of layers from his snow also collects and builds up the pressure, making the glacier more flexible. Gravity then pulls this ice downhill away from the zone of accumulation. The speed of this varies depending on whether it is a warm based or cold based glacier, and whether there is a large amount of ice being transported. Because the Athabasca is a temperate (warm-based) glacier, there is basal slippage occurring, which is the result of melt water running along the bedrock, therefore, the speed can be relatively fast for this glacier. Whereas the cold based glaciers do not move fast at all because of permafrost sticking them to the ground. The Athabasca falls down two icefalls in its course, these mean that the ice moving over these two icefalls moves much faster over them. Crevasses or transverse terraces which can be up to 30 meters deep form over these stretches of the ice as it moves over the ice steps. Mill holes which are similar to crevasses except they have water running through them, can be up to 60 metres deep and are also evidence that speed of the ice increases over the ice steps.
