types of glaciers Flashcards
1
Q
Polar environments
A
Areas of permeant ice
- Covers vast ice sheets of Antarctica and Greenland
- Long winters - short summers
- cold, snow storms, high winds
- Average temp = -49 -> -89.6 degrees
- Thin, infertile soil
- no nitrogen and carbon due to low decomposition levels
- Land mostly covered in ice
- Vegetation limited, short growing season
- Animal life = sea life > land based
2
Q
Alpine environments
A
- Mountainous areas in the European Alps, Himalayans, Andes, Iceland
- Seasonal change - cool climates, not all year snow coverage
- Soil thin and gravel like
- Poor in nutrients due to low rates of decomposition
- Vegetation low lying
- Mosses and linches lie at highest altitudes
- Coniferous trees adapt to snowy environments
- Mountain goats adapted to conditions
3
Q
Periglacial (tundra) environments
A
- At the edge of permanent ice, the environments characterised by permafrost
- includes: northern Canada, Alaska, Scandinavia, Siberia, Svalbard and Russia
- Temperature range from -7 degrees to +8 degrees in James Ross Island - NE America
- Soil deep, carbon filled, rocky due to frost shattering
- Vegetation limited -> Plant growth depends on depth of permafrost & thawing
4
Q
Glacial environments
A
- Found in both polar and alpine areas, very dynamic due to high rates of precipitation
- Found at high latitudes and altitudes
- Soil thin and infertile
- Depending on location its limited and low lying
- Found at the edge of the ice sheets
5
Q
Temperate glacier
A
- warm based glacier
- Located -> alpine or valley
- These melt in summer months
- Meltwater acts as a lubricant and reduces friction, erosion
- Transportation and deposition occurs
6
Q
Polar glacier
A
- cold based glacier
- Climate @ -40 degrees
- Movement per year = 1-2cm
- Typically ice caps or ice sheets
- Occur when temp is permanently below 0 degrees = no melting
- Frozen to their beds = movement internal & slow
7
Q
Pressure melting point
A
- The melting point of ice is 0°C at the surface of the ice can vary within the ice profile because of the pressure that the mass of ice exerts.
- At the base of a glacier ice can melt at below 0°C, ice moves with help of melt water
- Even if the air temperature is below freezing point.
- This is particularly relevant to temperate glaciers, but has no impact on polar glaciers.
8
Q
How warm based glaciers move
A
- basal slippage
- bed deformation
- Creep or regelation
9
Q
basal slippage
A
- Temperate glaciers move mainly via this
- If the glacier moves, this can raise the temperature of the base ice through pressure and friction.
- The basal ice can then melt, and this water helps to allow the ice to slip more easily over its bed.
- This could move at 2-3m per day and pick up material with which it can use to erode its bed.
- This is related to Regelation, melting under pressure and freezing again when the pressure is reduced.
EX - The Franz Joseph glacier, New Zealand moves 300m per year
Salmon Glacier, Canada = 45% - 90% movement via basal sliding - cold based cannot move via basal sliding as basal temp below pressure melting point and they are frozen to their bed*
10
Q
bed deformation
A
The material below the glacier becomes saturated due to the meltwater and moves taking the ice with it. 40-60m per year movement.
11
Q
creep / regelation
A
- Where an obstacle is encountered on the bed, pressure will increase.
- Stress on the ice builds up as it tries to overcome the obstacle the ice can behave like plastic and flows round or over the obstacle.
- The lower the temperature the greater the pressure that is needed.
- The bed over which the ice flows is not of even gradient.
- Where ice flows over steeply sloping gradient the ice movement would speed up, resulting in a thinner ice sheet with crevasses – an area of EXTENDING flow.
- BUT, where the ice flows over a gentler gradient the ice decelerates and backs up, creating an area of COMPRESSING flow.
12
Q
How cold based glaciers move - internal deformation
A
- Ice at 0 degrees deforms 100x faster than ice at -20 degrees
- These glaciers are frozen to the bed and therefore only move 1-2cm a day.
- Two types: intergranular flow and laminar flow
- Both processes occur on a slope not where ice is flat
EX - Meserve Glacier in Antarctica moves only 3-4cm per year by internal deformation
13
Q
Intergranular flow
A
- ice deforms
- if large stress/ pressure are applied it can crack in a brittle manner
- Forming crevasses
- due to basal and lateral drag glaciers low fastest in the centre, closet to the surface
14
Q
Laminar flow
A
- The ice crystals within the glacier orientate themselves in the direction of ice movement.
- This allows ice crystals to slide past one another.
- Where the ice movement is fast enough crevasses may develop
15
Q
glacial surges
A
- Ice can move at extraordinary speeds, and glaciers in surge conditions are known to move at up to 300m a day.
EX - The Franz Joseph glacier in New Zealand has been known to surge in the past. - Periodic, unpredictable and dangerous
- When a glacier flows unexpectedly between 10x and 100x faster
- Glacier becomes unstable in ablation zone = ice moves rapidly
- Unsure why this occurs -> potentially earthquake, build up of basal meltwater or increased precipitation
EX - Bruarjokull glacier, Iceland - galcier surged and advanced 45km forward at 5m per hour
