Glaciated Landscapes EQ 2 Flashcards
Components of a glacier system
Inputs Dynamic equilibrium Energy Outputs Stores and components Flows and transfers Feedback loops
What are inputs in glaciers
- Precipitation in the form of snowfall, which is compacted over many years to form high density ice.
- Avalanches
- Wind deposition, where strong winds at high altitudes deposit snow
Dynamic equilibrium
- Is the boundary between accumulation zone and ablation zone
- As balance shifts the equilibrium will move up or down
Energy
Glacier mass combined with gravity generate potential energy. As glaciers move down potential energy is converted into kinetic energy. This enables transportation, erosion and deposition
Outputs
Melt water
Ice calving where ice may break off to form icebergs
Evaporation or sublimation
Sublimation is where a solid changes to a gas with no liquid stage
Stores and components
Main stores are snow and ice which change seasonally
Over the last 40 years stores have been decreasing
Flow and transfers
Processes such as meltwater flow and processes of glacial movement such as internal deformation and basal sliding.
Flows and transfers are more active in warmer environments than colder ones
Feed back loops - negative
Wants to maintain dynamic equilibrium to minimise effect of outputs:
- Increased snowfall will increase volume of accumulation, with increased volume of accumulation there will be increases ablation. Glacier will maintain dynamic equilibrium.
Feed back loops - positive
AMPLIFY initial change and may cause a shift in the system to an new state of equilibrium:
- If a glacier has a positive ice mass balance, this increases the albedo effect due to high surface energy. This reduces air temperature causing the glacier to advance.
Factors that cause variation in rate of ablation
Solar radiation
Feedback loops
Warm base or cold base
Type of environment
Factors that effect the accumulation zone
Level of precipitation
Average temperatures
Insulation levels
Wind speeds - strong winds at high altitude deposit more snow.
Poleward aspect - south facing or north facing
Internal deformation
Happens in both warm and cold environments.
2 types of internal deformation:
- Intergranular flow, where ice crystals slip and slide over each other to flow downhill
- Laminal flow, where there is movement of individual layers within the ice
Extensional flow
An increasing gradient causes ice to flow faster and due to internal deformation the ice becomes stretched and crevasses are created.
Compressional flow
Reduction in gradient means ice flows slower. This cause the ice to pile up and thicken. Some crevasses close while some open up.
Between extensional and compressional flow, ice moves in a rotational manner
Transverse crevasses
Cuts across glaciers at right angles
Radial crevasses
Form in a splayed pattern at the snout of the glacier, where ice spreads out in a broad lobe.
Marginal crevasses
Forms near the side where there are different rates of movement due to friction at the sides.
Surge
A great amount of ice movement 100 times faster due to tectonic activity such as volcanic eruptions. This releases a great amount of meltwater which also acts as a lubricant.
Subglacial bed deformation
Sediment can dorm under the weight of the glacier, moving ice on top along with it.
Basal sliding
Happens in only warm base environments.
Involves the movement of large blocks of ice in short jerks. It occurs where meltwater is present to lubricate the base of the glacier.
2 types: enhanced basal creep, and regulation creep.
Regulation creep
Where basal ice melts under localised pressure when it encounters and obstacle. This allows the glacier to flow over it and when pressure is lowered the meltwater refreezes.
Enhanced creep
Where basal ice deforms around irregularities on the bedrock surface.
Feed back cycles of ice movement - negative
A negative feedback - at increasing ice depth the melting point of ice is lowered by pressure. As thickness increases, there is increased pressure and basal slip so ice move faster. In return this reduces ice thickness and reduces pressure melting point and basal slip.
Feed back cycle of ice movement - positive
An increase in basal melt water will increase basal slip, which generates frictional heat and increases basal slip.
