1. How can glaciated landscapes be viewed as a system? Flashcards
What is a system?
A set of interrelated objects connected together to form a working unit
INPUTS ———> STORES & PROCESSES ———> OUTPUT
A glacier is an OPEN SYSTEM: the inputs come from beyond the system boundary
Name the inputs:
Kinetic Energy - from movement of glacier and wind
Potential Energy - from energy stored within glacier affected by position of slope
Thermal Energy - from solar radiation and geothermal sources
Sediment - freeze thaw, rock falls etc.
Avalanche
Snowfall
Windblown particles
Name the stores:
Snow and ice
Debris
Potential Energy
Name the processes:
Erosional eg. Plucking and freeze thawing
Depositional
Weathering
Mass movement
Name the outputs:
Meltwater
Water vapour
Rock/Debris
Heat
What is dynamic equilibrium?
When the glacial system is disturbed it undergoes self-regulation and changes until equilibrium is restores
What is glacier mass balance? (Not needed but may be useful)
GLACIER MASS BALANCE is the difference between the amount of accumulation and the amount of ablation over a year.
EQUILIBRIUM LINE is found where Accumulation = Ablation
POSITIVE BALANCE is where Accumulation > Ablation eg. Winter
NEGATIVE BALANCE is where Accumulation < Ablation eg. Summer
The changing between positive and negative is known as DYNAMIC EQUILIBRIUM
Factors affecting glaciated landscapes:
CLIMATE
GEOLOGY
LATITUDE AND ALTITUDE
RELIEF AND ASPECT
Explain how climate affects glaciation:
- Aeolian processes (wind) can carry out erosion, transportation and deposition
- Precipitation determines the mass balance ———> inputs of snow, sleet and rain
- If temperatures rise above 0 degrees snow/ice starts to melt and becomes output
Explain how geology affects glaciation & give examples of rocks:
LITHOLOGY - physical and chemical composition of rocks
Clay has a weak lithology due to weak bonds so can’t resist erosion and weathering
Basalt has interlocking crystals so highly resistant eg. Pyramidal peak
Limestone is vulnerable to carbonation
STRUCTURE - properties of individual rock types eg. Jointing, bedding, faulting, permeability, angle of dip of rocks
Chalk is a porous rock so can absorb and store water
Carboniferous limestone is permeable due to joints
Explain how latitude and altitude affects glaciation & examples:
A glacier at high latitude but low altitude will be a large, stable ice sheet due to little seasonal variation in climate eg. Vostock Station, Antarctica has mean precip. total of 4.5mm per yr
A glacier at low latitude but high altitude is likely to melt more and be less stable due to large seasonal variation in climate eg. Jasper National Park in Rockies has mean precip. total of 600mm per yr (seasonal variations eg 25mm in January but 100mm in June)
Explain how relief and aspect affects glaciation:
Has an impaction the microclimate and the movement
The greater the relief, the greater energy the glacier will have to move downslope
If slope faces away from sun, temp. will be cooler so less melting and glacier can advance (+v.v)
How is glacial ice formed?
By diagenesis:
Fresh snow falls on top of previous years snow
Each new layer compresses the ice beneath it converting low density ice to high density ice
Firn (snow that survives one summer) has a density of 0.4 g/cm3
Glacial ice has a density of 0.83-0.91 g/cm3
What is a valley glacier?
A mass of ice that can be fed from an ice sheet or corries that is confined by valley sides
Typically 10-30km in length
What is an ice sheet?
Large accumulations of ice that extend for more than 50,000 km2
Currently only two - Antarctica and Greenland and contain 96% of world’s ice
Describe the Antarctic ice sheet:
Covers 13.6 million km2 and at its thickest is over 4700m deep (East)
What are the characteristics of warm-based glaciers?
Found at high altitudes
Steep relief
Basal temperatures at pressure melting point
Rapid rates of movement 2-200m per year
What are the characteristics of cold-based glaciers?
Found at high latitudes
Low relief
Basal temperatures below pressure melting point so frozen to bedrock
Very slow rates of movement, a few metres per year
What is pressure melting point?
When the pressure of the ice in the glacier is enough for melting to occur
(0 degrees at ice surface)
What factors influence the movement of glaciers?
Gravity Gradient Thickness of the ice (influences pressure melting point) Internal temp of the ice Glacial budget
What parts of the glacier move quicker than other parts?
James Forbes concluded in 1842 that the sides and base of the glacier move more slowly than the top and middle - due to ice being frozen to valley sides and floor
How does a warm-based glacier move (how) & example?
Basal sliding due to base temp. being above pressure melting point so meltwater formed
Consists of
Slippage: where ice slides over the valley floor due to reduced friction between the base of the glacier and the valley floor
Creep: where ice deforms under pressure, moves around objects, and then refreezes on other side as pressure is reduced on downside of obstacle
Bed deformation: where saturated material below glacier moves taking the ice with it
Eg. Basal sliding accounts for 45% of the movement of the Salmon glacier in Canada
How does a cold-based glacier move + example?
Moves by Internal deformation as basal temperature is below pressure melting point - about 1-2cm per year
Consist of:
Intergranular - individual ice grains sliding past each other
Laminar - layers of ice crystals sliding over each other
Eg Meserve glacier in Antarctica moves 3-4 metres per year and 100% due to internal deformation
Name the two types of glacial mass movement:
Extending and compressing flow - when ice cannot move quick enough over a steep slope so fractures to form crevasses
When the gradient is reduced, compressing flow occurs as the ice thickens
Glacial Surge - when a glacier flows on a steep slope between x10 and x100 times faster than normal and can be caused by; earthquakes, basal meltwater buildup or increased precipitation
Eg Glacier on Disko Island, Greenland moved 10km in four years
