Glaciated Landscapes Flashcards
What is a glacier’s bed load?
- Sediment dragged along the base of a glacier then deposited over a large area
What is the accumulation zone?
- Net accumulation is greater than net ablation
- Top part of a glacier
What type of system are glaciated landscapes?
- Open system
- Both energy and matter cross the system’s boundaries
Explain what a closed system is.
- A system with inputs and outputs of energy
- No movement of materials across system boundaries.
Name 4 glacial inputs, throughputs and outputs.
- Inputs: precipitation, meltwater, debris, thermal energy
- Throughputs: snow, ice, debris, meltwater
- Outputs: water vapour, debris, meltwater, thermal energy
What is a glacial mass balance?
- AKA glacial budget
- Difference between accumulation and ablation over one year
What is the ablation zone?
- Where net ablation is greater than net accumulation
- Lower part of glacier
What is the equilibrium line in terms of a glacier’s mass balance?
- Where accumulation is equal to ablation
- Dynamic and theoretical
How would you calculate the annual budget of a glacier?
- Subtract total ablation from the total accumulation
- Positive values means net accumulation
- Negative values means net ablation
What are aeolian processes?
- Erosion, transportation and deposition carried out by wind
How can lithology influence glaciated landscapes?
- Lithology - physical and chemical composition of rocks
- Rocks with weak lithology (eg clay) have little resistance to erosion
- Basalt has strong lithology so is resistant and forms prominent landforms
How does structure of rocks affect glaciated landscapes?
- Concerns jointing, bedding, faulting and permeability
- Angle of dips of rocks which can influence valley side profile
How does latitude influence glaciated landscapes?
- At 66.4º N and S - cold, dry climates, little seasonal variation
- Glaciated landscapes develop through large, stable ice sheets
Define lithology.
- The physical and chemical composition of rocks
How does lithology impact the formation of landforms?
- Weak lithology rocks easily eroded e.g. clay
- Strong lithology rocks rarely eroded e.g. basalt
Define structure.
- Properties of individual rock types including jointing, bedding and faulting
How does structure affect the formation of landforms?
- Some rocks are permeable, like limestone, while granite is impermeable
How does relief affect the formation of landforms?
- Steeper relief causes greater acceleration due to gravity so more erosion
How does aspect affect the formation of landforms?
- If facing away from sun, temperatures remain below zero for longer so less melting occurs and ice forms
What are the components of a system?
- Inputs, throughputs and outputs, stores and flows
What are the flows of energy of a glacial system?
- Kinetic energy in the movement of ice and material
- Potential energy in the vertical height of material
- Thermal energy in the absorption of solar energy
How does climate impact a glacial system?
- Inputs of precipitation increase the mass of a glacial system
- Small inputs restrict growth
- Large seasonal variation causes large variation in glacial mass
Define latitude.
- Measurement of distance north or south of Equator
How can altitude impact a glacial system?
- Higher inputs
- More seasonal variation
- Some glaciers near Equator
Summarise the formation of glacial ice.
- Fresh snow (0.05 g/cm^3)
- Firn (0.4 g/cm^3) - one year
- Glacier ice (0.83-0.91 g/cm^3) - 30-1000 years
How deep is true glacial ice found?
- 100m
What is firn?
- Snow that has survived one summer
- AKA neve
What is the term for the formation of glacial ice?
- Diagenesis
What are the two types of glacier?
- Valley glacier/warm-based
- Ice sheet/cold-based
Define an ice sheet and give two named examples.
- Accumulations of ice greater than 50,000km^2
- Greenland, Antarctica
Outline the size of the Antarctica ice sheet.
- Area - 13.6 million km^2
- Volume - 30 million km^3
- Depth - 4700m
Outline typical size of a valley glacier.
- 10-30km long
- 1km thick
Give four characteristics of valley glaciers.
- High altitude
- Steep relief
- Basal temps at PMP
- Rapid movement - 20-200m per year
Give four characteristics of ice sheets.
- High latitude
- Low relief
- Basal temp below PMP
- Slow movement - <10m per year
Define pressure melting point (PMP).
- Temperature where ice is about to melt
What five factors impact movement of glaciers?
- Gravity
- Gradient
- Thickness of ice
- Internal temperature
- Glacial budget
What are the two typical zones of glacial ice movement?
- Upper zone - brittle
- Lower zone - deforms
What type of glacier moves by basal sliding?
- Warm-based/valley glaciers
What is basal sliding?
- Basal temp at PMP
- Thin meltwater reduces friction
- Ice moves down valley
What mechanisms are involved in basal sliding?
- Slippage
- Creep
- Bed deformation
How much movement is basal sliding often responsible for and what is the extreme of this?
- Often 45%
- Extreme - 90%
Why is basal sliding rarely seen in cold based glaciers/ice sheets?
- Basal temp too low
What are the two components of internal deformation?
- Intergranular flow
- Laminar flow
What is inter granular flow?
- Individual crystals re-orientate and align
What is laminar flow?
- Movement of layers of ice within glacier
What is extending flow and when does it occur?
- Ice moving over steep slope fractures
- Ice unable to deform fast enough
- Leading ice pulls away from ice behind
- Forms crevasses
What is compressing flow and when does it occur?
- Gradient of slope decreases
- Ice thickens
- Flowing ice moves over slower ice
- Layers called planes - slip planes
What is a glacial surge and what can cause it?
- Rapid movement - 100s meters per day
- Steep gradient and large inputs of snow
- Tectonic activity
Name an example of a glacial surge.
- Disko Island, Greenland
- Moved 10km between 1995-1999
What are the three types of weathering?
- Physical
- Chemical
- Biological
Define physical weathering.
- The breakdown of rock into smaller fragments with no chemical alterations
Why are some weathering processes not significant in glacial landscapes?
- Temperatures are too low
- They are ineffective
What are the three main physical weathering processes in glacial landscapes?
- Freeze-thaw
- Frost shattering
- Pressure release
Outline the process of freeze-thaw.
- Water enters cracks in rock
- Expands 9% when freezing
- Pressure makes cracks expand
- Continued changes causes breaks
- More temp changes makes it more effective
Outline the process of frost shattering.
- Very low temperatures
- Water in rock pores expands
- Stress causes disintegration
Outline the process of pressure release.
- Weight of overhead ice lost due to melting
- Rock under expands and fractures parallel to surface
- AKA dialation
- Exposes underlying rock
Define chemical weathering.
- Chemical reaction between elements in weather and minerals in rocks
- It may reduce rock to constituent chemicals or alter composition
What are the five main chemical weathering processes?
- Oxidation
- Carbonation
- Solution
- Hydrolysis
- Hydration
Outline the process of oxidation.
- Minerals eg iron react with oxygen in air/water
- Becomes highly acidic
- Structure destroyed
Outline the process of carbonation.
- Rainwater combines with CO2 in atmosphere forming carbonic acid
- Acid reacts with carbon carbonate forming calcium bicarbonate
- process is reversible
- precipitation forms stalactites and stalagmites
Outline the process of solution.
- mineral dissolves in water
Outline the process of hydrolysis.
- Chemical reaction between minerals and water to make secondary minerals
- e.g. Feldspar in granite reacts with hydrogen to form kaolin (china clay)
Outline the process of hydration.
- Water molecules mix with minerals to make larger volume minerals
- e.g. Anhydrite forming gypsum
