Cold Environments

Front 1

What are glaciers?

Back 1

Large bodies of ice formed from compressed snow. They move slowly downslope under their own weight and gravity.

Front 2

What are the three main types of glacier?

Back 2

Ice sheets

Icefields (ice caps)

Valley glaciers

Front 3

Describe the different types of glaciers and compare. Give an example of where each is found.

Back 3

Ice sheets: largest glaciers often being more than 2-3km thick, submerging the landscape. Found only in Antarctica and Greenland.

Icefields: miniature ice sheets, covering areas of less than 50,000 km2. Form in plateau-like uplands such as Vatnajokull in southest Iceland.

Valley glaciers: giant tongues of ice that flow down from the snowline in mountainous regions such as Alaska and the Alps.

Front 4

What are the different forms of valley glaciers.

Back 4

Cirque glaciers: small mountain glaciers, confined to bowl-shaped depressions at the head of glacial valleys.

Outlet glaciers: valley glaciers that flow from icefields.

Piedmont glaciers: when valley glaciers leaving the mountains spill out into lowland regions and merge.

Front 5

What are the three types of climate where glaciers are found?

Back 5

Glacial

Periglacial

Mountain

Front 6

Describe a glacial (polar) climate.

Give an example of a polar climate.

Back 6

Contain snow and ice all year

Very cold and relatively dry

Antarctic - variation in amount of precipitation.

Front 7

Describe periglacial climates.

Back 7

Significant cover of snow and ice, not all year

Found in high altitudes/latitudes

Characterised by large seasonal temperature ranges

Areas are cold because:

high latitude - little insolation due to low angle of overhead sun

high altitude - temps decline on average 1 degree for every 100m

albedo - reflect much solar radiation.

Precipitation levels low as cold air can only hold small amounts of moisture

Front 8

Describe mountain (upland/alpine) climates.

Give an example of an area.

Back 8

Once covered in ice, now free of snow and ice

Landforms continue to exert influence on people who live there

Many are periglacial but some are so high up they contain glaciers and ice caps - Alps, Himilayas

They are cool

Wet - areas often cause relief or orographic rainfall

Front 9

What is orographic rainfall?

Back 9

Rain produced as air is forced to rise over high ground such as a mountain barrier, it subsequently cools, condensation occurs, and precipitation is produced.

Front 10

What processes occur in glacial environments?

Back 10

Plucking

Abrasion

Freeze-thaw weathering

Chemical weathering by meltwater

Front 11

Describe plucking.

Back 11

Ripping out of material from bedrock

The more freeze-thaw there has been previously, the more effective plucking becomes.

Occurs mainly at base of the glacier, also on sides

Involves downward pressure (due to weight of ice) and downhill drag as ice moves, slow enough for melt water to freeze onto obstacles.

The prised material can be used for abrasion.

Front 12

Describe abrasion.

Back 12

Erosion of the bedrock by material carried by the glacier. The larger and more angular the load, the greater the potential for erosion. The coarser material will scrape, scratch and groove the rock, leaving striations and chatter marks.

Front 13

Define striations and chatter marks.

Back 13

Striations: scratch marks on a rock caused by abrasion.

Chatter marks: discontinuous scratch marks on a rock caused by abrasion.

Front 14

What factors affect the rate of abrasion?

Back 14

Presence of debris in basal ice - rate of abrasion will increase with debris concentration up to the point where effective basal sliding is restricted

Sliding of basal ice - ice frozen to bedrock cannot erode unless already contains rock debris, the faster the rate of basal sliding, the faster the rate of abrasion.

Relative hardness of debris particles and bedrock - most effective abrasion when resistant rock particles pass over weaker bedrock.

Front 15

What factors affect the rate of abrasion?

Back 15

Ice thickness - the greater the thickness, the greater the vertical pressure exerted on particles on glacier bed, more effective abrasion. Up to the point where friction between particles and the bed becomes so high that movement is significantly restricted and abrasion decreases.

Debris particles size and shape - angular debris will be more efficient than rounded debris.

Efficient removal of fine debris - high levels of abrasion, fine particles need to be removed from the ice-rock interface. Melt water appears to be the main mechanism for the removal of fine debris.

Front 16

Describe freeze-thaw weathering.

Back 16

Rock fracture due to pressure release, exfoliation and dilatation. Pressure release occurs during and after deglaciation - removal of the overlying glacier leads to a massive decrease in the weight/pressure pushing down on the underlying rock. Reduction in pressure = rock expands upwards and outwards leading to formation of cracks and lines of weakness in upper part of underlying rock. Following rapid erosion, exfoliation may occur. Freeze- thaw will cause the expansion and contraction of joints (dilation) which leads to fracturing. It is more likely to be attacked effectively by a glacier in a future glacial advance.

Front 17

Describe chemical weathering by meltwater.

Back 17

Important on carbonate rocks. CO2 is more soluble at low temps, hence meltwater streams have the capacity to hold much CO2. As they become more acidic, able to weather carbonate rocks more effectively.

Front 18

What factors does the rate of glacial erosion depend on?

Back 18

Local geology - areas with well-fractured, jointed bedrocks are easily plucked.

Velocity of the glacier - somewhat dependent on gradient, areas of fast-flowing ice lead to increased erosion.

Amount and character of the load carried by the ice - if load is coarse, resistant and angular, it will erode mire than a load that is fine, weak and rounded.

Front 19

What processes occur in periglacial environments?

Back 19

Ice action

Solifluction

Chemical weathering

Front 20

Describe ice action.

Back 20

Dominated by freeze thaw weathering - occurs when temperatures fluctuate above and below freezing point. As water freezes it expands by 10%. Most effect on well-jointed rocks, which allow water to seep into cracks and fissures.

Frost heave is the process where water freezes in the soil and pushes the surface upwards and churns it. Ice-lensing refers to the growth of ice crystals in soil. Nivation refers to freeze-thaw weathering under a snow bank.

Front 21

Describe solifluction.

Back 21

Flowing soil and is an accelerated form of soil creep. In winter, water freezes in the soil causing expansion of the soil and segregation of individual soil particles.

In spring the ice melts and water flows downhill It cannot infiltrate the soil because of the impermeable permafrost. As it moves over the permafrost, it carries segregated soil particles and deposits them further downslope as a solifluction lobe or terracette.

Front 22

Describe chemical weathering.

Back 22

Carbonation is an important process because of the low temperatures. Carbon dioxide is more soluble at low temperature hence the water becomes quite acidic. Aided by the slowly rotting vegetation which releases organic acids.

Hydration is the process where certain minerals absorb water, expand and change.

Front 23

List the erosional features of cold environments.

Back 23

Cirques

U-shaped valleys

Fjords

Roche mountonees

Erratics

Striations

Front 24

What is till?

Back 24

Sediment deposited by a glacier - unsorted, angular and of variable sized material, till refers to unsorted deposits with a wide range of grain size, deposited directly by ice - whether on land or below a floating glacier - and not subsequently changed. Sometimes called moraine.

Front 25

Describe the formation of a cirque.

Front 26

Describe the formation of u-shaped valleys.

Front 27

Define pressure release.

Back 27

Type of weathering in which rock expands outwards as a result of the 'unloading' of weight and as a result fractures or cracks appear in the rock as it expands.

Front 28

Define spur.

Back 28

Projection of land from a ridge/mountain. Truncated spurs are those which have been eroded in their lower parts by glaciers.

Front 29

Define ribbon lakes.

Back 29

Long, linear lakes which fill a glaciated trough.

Front 30

What is a hanging valley?

Back 30

A small u-shaped valley formed by a small glacier that joins and hangs above a large U-shaped valley formed by a large glacier.

Front 31

What is scree?

Back 31

Angular sediment that collects at the foot of a mountain range or cliff. The rock fragments that form scree are usually broken off by the action of freeze-thaw weathering.

Front 32

What is moraine?

Back 32

Glacial deposits consisting of poorly sorted, often angular, loose rock fragments. Many forms exist including englacial, lateral, medial, recessional and terminal.

Front 33

Describe how a fjord occurs.

Front 34

What is isostatic uplift?

Front 35

What feature results from meltwater (fluvioglacial) erosion?

Back 35

Meltwater channels

Front 36

What features result from glacial deposition?

Back 36

Erratics

Till

Moraine

Drumlins

Front 37

Define unstratified material.

Back 37

Usually glacially deposited material which is unsorted, variable in size and has no distinct layers.

Front 38

Define ablation.

Back 38

The removal of material (ice, debris) from a glacier such as by melting, evaporation and sublimation.

Front 39

Explain erratics and how they occur. Give an example of an erratic.

Back 39

Large boulders foreign to the local geology that have been dumped by the ice, usually on flat areas.

Some have been left stranded in precarious positions as perched blocks such as Fishguard in Dyfed.

Front 40

Explain what till is.

Back 40

Common, widespread and unstratified glacial deposit composed of finely grained rock flour mixed together with rocks of different shapes and sizes. Composition is variable.

Two types:

Lodgement till - dropped by actively moving glaciers

Ablation till - dropped by stagnant ice

Front 41

Explain moraines.

Front 42

Define moulins.

Back 42

A circular sink-hole or portal into a glacier. They may be caused by meltwater entering a crevasse.

Front 43

Describe the formation of a drumlin.

Back 43

Some low-lying, undulating regions, particularly where a valley glacier flows into a lowland plain (causing thinning of the ice), the till is deposited as small, oval mounds a few metres long and high. .................................

Front 44

What features occur from fluvioglacial deposits?

Back 44

Prolonged drift

Ice contact stratified drift

Eskers

Kames

Front 45

Explain prolonged drift.

Back 45

Consists of material dropped in glacial lakes and along lake shorelines.

With recession of continental ice sheets and large ice bodies, lakes frequently formed as temporary features. Material was deposited in these lakes, brought down by seasonal meltwaters.

Summer deposition is indicated by a layer of coarse deposits.

Winter deposition is indicated by a thinner layer of finer material.

Front 46

Explain ice contact stratified drift.

Back 46

Consists of stratified sand and gravel that is sorted by the action of meltwater streams and deposited next to the glacier. They are modified as the result of ice retreat.

Front 47

Explain eskers.

Back 47

Elongated ridges of coarse, stratified fluvioglacial material. The ridges usually meander (Scandinavia) between lakes and marshes.

One theory - material deposited in subglacial meltwater tunnels during a period of ice stagnation.

Another theory - some eskers could be elongated deltas, deposited by streams flowing out from tunnels at the front of a continuously and rapidly retreating ice front.

Front 48

What are kames?

What is a typical characteristic of a kame?

Back 48

Irregular mounds of bedded sands and gravels,

arranged in a chaotic manner.

It has a small, shallow hollow - called a kettle hole amid the kame mounds.

Front 49

What is a true kame?

Back 49

A small delta, formed where a meltwater stream flowed out beneath an area of stagnant or slowly decaying ice, into a lake dammed between the ice front and drift material.

Front 50

List the periglacial features.

Back 50

Patterned ground

Pingos

Ice wedges and ice-wedge polygons

Front 51

Describe patterned ground.

Back 51

Variety in shapes such as garland (elongated circles), polygons and stripes.

Some is sorted and some unsorted.

Cause: frost heaving helps to move larger stones to the surface, fine grained stones forms the raised core, while the stones form the edges of the pattern. Another cause is the cold which creates cracks which stones may roll into.

Surface wash is important for the formation of stripes.

Front 52

Describe open - system pingos.

Back 52

Isolated, conical hills up to 100m in height and may have diameter of up to 1km. Form as a result of the movement and freezing of water under pressure.

Open-system pingos: the source of the water is from a distant, elevated source. These are largely found in areas of discontinuous permafrost. Groundwater forces its way to the surface and freezes.

Front 53

Describe closed - system pingos.

Give an example of an area where pingos are found.

Back 53

Close-system pingos: isolated features on flat surfaces. Associated with areas of continuous permafrost. Formed when a lake in permafrost area is in-filled with sediment - cause increase in insulation and permafrost to expand. Traps a body of water (talik), which freeze, expands and creates a pingo.

Nearly 1400 pingos are found in the Mackenzie Delta of Canada - 98% are closed system.

Front 54

What is continuous permafrost?

Front 55

What is discontinuous permafrost?

Front 56

What is sporadic permafrost?