1.a-c How can glaciated landscapes be viewed as systems?

time scale of glacial systems?

from a few days to millennia

main inputs of glaciated systems

- energy

- precipitation/snowfall

- matter/material from deposition, mass movement, weathering, avalanches

main outputs of glaciated systems

- calving

- sublimation

- evaporation

- ablation

what is the accumulation zone?

- where accumulation exceeds ablation

- snowfall and eventually ice formation occurs here

what is the ablation zone?

- where ablation exceeds accumulation and separated by equilibrium line altitude

what is the equilibrium line altitude?

- balance of inputs and outputs

what is the glacier mass balance?

- difference between amount of snow and ice accumulation and the amount of ablation occurring in a glacier over a one year time period

what is the flow of energy in glaciated systems?

- the potential energy from the altitude of the glacier is transferred to the kinetic energy store of the glacier as it moves which is converted into thermal energy via friction and dissipates into atmosphere

what is dynamic equilibrium?

- when equilibrium is disturbed the system undergoes self regulation and changes til equilibrium is restored

why does the equilibrium line move up in summer?

- snow can only last at higher elevations due to seasonal changes in temperature, moving the equilibrium line uop

what is a positive regime?

- more accumulation than ablation

how much has meltwater from glaciers raised sea level?

- 2.6 cm - 10 000 billion tonnes

what are the influences on glaciated landscape systems?

- climate

- latitude + altitude

- geology

- relief and aspect

difference between latitude and altitude

- latitude = how north or south of the equator

- altitude = how many meters above sea level

how does the climate influence glaciated systems? (8)

1) Affects ice accumulation and mass balance

- If temperatures are below 0, input is snow

- As snow accumulates into glacier it compresses over years to form ice. This is only if there is more accumulation than ablation. - a positive regime

- the glacier advances if it is a positive regime

- as a glacier advances it will erode via plucking and abrasion

- this is apart of the formation of corries, aretes

2) affects erosional processes

- if there is greater seasonal variation in temperatures around 0 this enables freeze thaw and frost shattering

- this creates scree as a result and has mulitplier effect

- this forms arretes, corries and pyramidal peaks

3) affects temperature of glacier

- warm based versus cold based glaciers

- determines pressure melting point

- due to pressure ice exists at liquid below 0 degrees

- therefore a layer of meltwater lubricating between glacier and earth

- this reduces friction and encourages erosion via plucking and abarsion

- corries and U -shaped valleys created

what is lithology?

- physical and chemical composition of rocks

what is structure?

- properties of individual rock types e.g. jointing, bedding and faulting

how does lithology affect glaciated systems?

1) hardness of rock

- certain types of rock have stronger bonds between particles which require more energy to break

- this is reflected for example in Basalt in the form of dense interlocking crystals.

- harder rocks include granite and bedrock

- this means less erosion occurs and thus fewer landforms are formed in areas of harder rock and vice versa for softer bands of rock

2) solubility of rock in acids

- rainwater becoming increasingly acidic due to increases conc of CO2 in atmosphere and becoming carbonoic acid

- if soluble in weak acids, more vulnerable to decay by chemical weathering e.g. limestone

- rock dissolves and accelerates modification of landscape

how does structure of rocks affect glaciated systems

rock structure

- if a rock is porous, water is absorbed and stored 'primary permeability'

- enables freeze thaw weathering where water in pores will expand by 10% etc etc

- speeds up formation of corries, pyramidal peaks and U shaped valleys and more of them

- e.g. chalk is porous

how do latitude and altitude affect glaciated landscapes? (4) → think meltwater, climate, cold/warm based, temperature variation

High latitude — polar regions

e.g. Vostok, Antarctica, Arctic Canada

Low solar radiation → dry climate with little seasonal variation → minimal freeze-thaw cycling → little erosion, few landforms

→ low snowfall + temps rarely cross 0°C → no meltwater layer forms at base → glacier frozen to bed → cold-based, slow movement

High altitude, lower latitude — alpine

e.g. Alps, Andes, Himalayas, Rockies

Mid-latitude moisture + orographic uplift → high precipitation → positive mass balance → More movement

→ ice pressure + geothermal heat → basal meltwater layer forms → glacier decoupled from bed → warm-based, slides 20–200m/yr

→ variable temps → active freeze-thaw, plucking, abrasion → extensive erosional landforms

how do relief and aspect affect glaciated landscapes? (4)

- impacts the micro climate and the movement of glaciers

- the steeper the relief the greater resultant force of gravity and more energy a glacier will have to move downslope

- if the aspect of a slope faces away from the general direction of the sun (north facing), temperatures remain below 0 for longer as less solar energy is received so less melting occurs so mass balances tends to be positive and glacier advances .

- glaciers with a positive mass balance are likely to be larger with a greater erosive power and more erosive than smaller ones which retreat due to a negative mass balance.

aspect meaning?

compass direction a slope faces

how does glacier ice form?

- glaciers form when temperatures are low enough for snow to stay frozen the entire year

- fresh snow = flakes with an open feathery structure and low density <0.1g/cm cubed (90% air)

- each new fall of snow compresses and compacts the layer beneath causing air to be expelled and converting low density snow into higher density ice.

- survived one summer = firn - 0.5-0.7 g per cm cubed

- glacier ice due to further compaction density 0.83 and 0.91 g/ cm cubed diagenesis

- depth = 100m

order of snow to ice

1) snowflakes 0.1

2) firn 0.5-0.7

3) glacier ice 0.83- 0.91

characteristics of ice sheets

- largest accumulation of ice = extends more than 50 000km2

- Antarctica and Greenland = 13.6 million km squared and consists a volume of 30 million metres cubed

- 4700m deep

- 96% of the world's ice

characteristics of valley glaciers

- confined by valley sides

- might be fed from snow and ice from one or more corrie glaciers

- typically between 10km and 30km in length

characteristics of warm based glaciers

- high altitude locations outside polar regions

- steep relief

- basal temperatures at or above melting point

- rapid rates of movement 20-200m annually

- because of increased pressure of overlying ice, water exists as a liquid at temperatures below 0 degrees causing basal ice to melt continuously

- thin layer of meltwater lubricating movement

characteristics of cold based glaciers

- high latitude locations

- low relief

- basal temperatures below pmp so frozen to the bedrock

- very slow movement with only a few metres of movement annually

- accumulation of heat from geothermal sources is not great enough to raise temps to 0 degrees

- relatively little surface melt in short summer

how do glaciers move?

- forces of gravity

- ice moves downslope from higher to lower altitude

- in valley glaciers this involves moving from accumulation zone across equilibrium line into ablation zone

factors affecting movement of glaciers

- gravity

- gradient

- thickness of the ice - this affects basal temperature and pmp

- internal temperatures of ice - allows movement of ice relative to others

-

what is the pressure melting point?

- the temperature at which ice melts when under pressure

what is basal sliding?

- typically how warm based glaciers move

- occurs as temperature of basla ice is above pressure melting point

- therefore thin layer of meltwater to lubricate movement

- it facilitates glacier movement as friction is reduced and so the ice can slide over the valley floor

- rates of movement greatly depend on the availability of meltwater

- meltwater is increased by a rough valley floor as this increases friction, the heat from which is used to produce more lubricating meltwater

what is internal deformation?

- The glacier also flows when temperatures are too cold for basal flow.

- When temperatures are very cold, the glacier moves like plastic.

- often results in crevasses due to large stresses and pressure

- The speed is affected by the gradient of the slope. The steeper the slope, the faster the flow. This process is known as internal deformation.