open system with inputs, outputs, processes and stores.
- INPUTS = Precipitation (primarily snow), Avalanches and the Zone of Accumulation
- STORES = Ice
- PROCESSES = Plucking, Abrasion, Flows (all the different types), Ablation, Accumulation and Freeze-thaw
- OUTPUTS = Meltwate, Moraine, Zone of Ablation
- Loose snow settles
- As it becomes more dense it turns into Firn (which is also known as Neve) and then further alterations in weather (as seasons change etc) provoke freezing and thawing which converts the loose snow into icy granules
- As more snow falls, it get more and more compacted. This creates pressure between the individual granules and therefore initates pressure melting
- Eventually this turns into a dull, white, structureless mass that is less permeable than fresh snow
- Air is squeezed out of the ice particels as they are forced to fuse together after further compression by the extra weight of additional ice and snow. This process is known as sintering.
- The resulting glacier takes a blue tinge and contain very few air spaces, making it impermeable to water
Glaciers grow and retreat......
- When the rate of accumulation is greater than that of ablation the glacier advances = positive regime
- When the rate of accumulation is less than that of ablation the glacier retreats = negative regime
- In cold glaciers, the ice is very hard and frozen, right to the bedrock. This is because temperatures stay below freezing point all year round. The absence of meltwater greatly restricts movement and the erosive ability of the glacier.
- Within the ice ---> englacial
Debris falls down through cracks and crevasses in the ice.
- At the base ---> subglacial
This is a mixture of material scarped up from below the glacier and that which has made its way downwards through crevasses, with or without the help of meltwater streams within ice.