COLD ENVIRONMENTS

COLD ENVIRONMENTS

HideShow resource information
  • Created by: elliel97
  • Created on: 18-03-14 20:07

GLACIAL (POLAR) CLIMATES

GLACIAL (POLAR) CLIMATES

  • Contain snow and ice all year round
  • Very cold and relatively dry
  • Variation in precipitation
  • Variation in wind. Can have kabatic winds.
1 of 41

PERIGLACIAL CLIMATES

PERIGLACIAL CLIMATES

  • Significant cover of snow and ice but not all year round
  • Found in areas of high altitude and latitude 
  • Large seasonal temperature ranges.
  • Cold due to high altitude: small amount of insolation due to long angle of overhead sun and high latitude: temperatures decline on average 1 degree celcius every 100m and albedo: they reflect much solar radiation (avg absorption for dark soils is 90% avg absorption for snow and ice is 10-20%
  • Precipitation levels are low due to: low air temperature since cold air is only able to hold small amounts of moisture andhigh pressure conditions.                                       
2 of 41

MOUNTAIN (UPLAND) CLIMATES

MOUNTAIN (UPLAND) CLIMATES

  • Were once covered in ice but are now free from snow and ice.
  • Many upland areas are periglacial
  • Some can be so high that they contain glaciers and ice caps (Alps, Himalayas) 
  • They are cool - lose 1 degree celsius every 100m 
  • They are wet - mountainous areas often cause relief or orographic rainfall
3 of 41

PROCESSES IN COLD ENVIRONMENTS

PLUCKING:

  • The ripping out of material from the bedrock
  • Occurs at the base mainly, but also at sides
  • Process: 

1) Downward pressure is caused by the weight of the ice.

 2) It is also caused by the downhill drag as the ice moves is slow enough for meltwater to freeze onto the obstacles. 

3) Once the material has been prised out of the bedrock, it can be used for abrasion of the landscape.

4 of 41

PROCESSES IN COLD ENVIRONMENTS

ABRASION:

  • The erosion of bedrock material carried by the glacier
  • The larger and more angular the bedload, the greater the potential for erosion
  • The coarser material will scrape, scratch and groove the rock, leaving striations and chatter marks.
  • The finer material will smooth and 'polish' the rock
  • E.G. = Brediamerkurjokull glacier in Iceland. 
5 of 41

PROCESSES IN COLD ENVIRONMENTS

FREEZE-THAW:

  • As water freezes, it expands by 10%
  • This exerts pressures of up to 2100kg/cm2 and most rocks can withstand only 210kg/cm2 
  • Most effective on well jointed rocks which allow water to seep through into cracks and fissures
  • It causes rocks to split (congelifraction)
  • Occurs when temperatures fluctuate above and below freezing.
6 of 41

PROCESSES IN COLD ENVIRONMENTS

FROST HEAVE:

  • The process where water freezes in the soil and pushes the surface upwards and churns it.
7 of 41

PROCESSES IN COLD ENVIRONMENTS

PRESSURE RELEASE:

  • The removal of the overlying glacier (after deglaciation) leads to a massive decrease in the weight or pressure pushing down on the underlying rock.
  • With the removal of pressure, the rock expands upwards and outwards, often leading to the formation of cracks and lines of weakness in the upper parts of the underlying rock
  • These lines of weakeness are exploited by frost weathering and glacial erosion if glacial conditions return.
8 of 41

PROCESSES IN COLD ENVIRONMENTS

CHEMICAL WEATHERING - BY MELTWATER:

  • The water released by the melting of snow or ice.
  • Important below glaicers - It's presence is due to intense pressure which causes melting.
  • Meltwater lubricates the base of the glacier, reducing friction and allowing theice to move freely. Pressure melting and refreezing is common at the base of the ice. 
  • Effective on carbonate rocks because CO2 is more soluble at low temperatures hence meltwater streams have the capacity to hold much CO2. As the streams become more acidic (CO2 = acidic) they are able to weather carbonate rocks more effectively.
9 of 41

PROCESSES IN COLD ENVIRONMENTS

CHEMICAL WEATHERING - CARBONATION:

  • A form of weathering in which calcium carbonate reacts with an acid water to form calcium bicarbonate which is soluble and removed in solution.
  • At lower temperatures CO2 (carbon dioxide) is more soluble in the atmosphere and can dissolve in rainwater forming a weak carbonic acid (this is more commonly known as acid rain) which reacts with limestone dissolving it. 
10 of 41

PROCESSES IN COLD ENVIRONMENTS

CHEMICAL WEATHERING - HYDROLYSIS:

  • A chemical weathering process where water reacts with minerals such as feldspars to produce clay minerals.
  • If joints in the bedrock are closely spaced the increased surface area increases the extent of the hydrolysis, effectively rotting the granite.
  • Important because of the large presence of organic acids in marshy soils
11 of 41

FEATURES OF COLD ENVIRONMENTS

CIRQUE:

  • An armchair shaped hollow surrounded by knife-edged ridges called aretes.
  • Located at mountain heads
  • Source of valley glaciers in alpine regions
  • The outlet to the cirque has a raised lip of moraine or solid rock

Formation:

  • A shallow, preglacial hollow is the original site of snow accumulation
  • The hollow is enlarged by freeze-thaw weathering at the edge of the snow patch (nivation)
  • Continued nivation enlarges the hollow and neve forms
  • Gradually the basin further develops and ice accumulates
  • At a critical depth and weight of ice, the ice moves out of the hollow by extrusion flow (the movement of ice as a result of becoming too deep or heavy and therefore unstable) in a rotational manner
  • This rotational movement of ice helps to erode the hllow further by plucking and abrasion
12 of 41

FEATURES OF COLD ENVIRONMENTS

ARETE:

  • When two cirques lie back to back, cirque englargement by headwall recession will create a narrow, steep-sided ridge between the two, called an arete
13 of 41

FEATURES OF COLD ENVIRONMENTS

PYRAMIDAL PEAKS:

  • If 3 or more cirques develop, the central mass between them will become a pyramidal peak 
  • It is sharpened by freeze-thaw weathering
  • E.G = The Matterhorn - Pennine Alps on the border between Switzerland and Italy (a horn is an isolated upstanding mass of rock)
14 of 41

FEATURES OF COLD ENVIRONMENTS

U-SHAPED VALLEY

  • An erosional feature of cold environments
  • Present form depends on subsquent activity since last glaciation
  • Parabolic
  • Result from the channelling of ice through valleys, combining freeze-thaw, plucking and abrasion

Formation:

  • Before onset of glaciation, active freeze-thaw weathering under periglacial processes will weaken the floor and sides, preparing it for rapid erosion
  • During interglacial phases, periglacial periods will return, further weakening the eroded rock
  • During glaciation, the eroding power of the ice will cause the valley to become 'U' shaped in cross section with a flat floor and steep sides
  • It will become straight in plan view (As oppose to the winding nature of the former valley) as the interlocking spurs are bulldozed to leave truncated spurs.
  • Extrusions in the ice can cause the ice to erode deep rock basins in the valley floor, later occupied by ribbon lakes (lakes which fill a glaciated trough) 
  • As the ice moves along, it also erodes rock steps by scoruing out lines of weaker rock, by opening up major lines of weakness or by experiencing periods of intense extrusion flow
15 of 41

FEATURES OF COLD ENVIRONMENTS

HANGING VALLEYS:

  • (Contiuning from U-shaped valleys) The addition of a tributary glacier can also develop rock steps due to the increased erosion associated with a thicker mass of ice
  • Some glacial throughs end abruptly at their head in a steep wall (the trough end)
  • The small tributary glacier has neither the weight nor the power to cute down to the depths of the main trough
  • When the ice disappears, these tributary galcial vallelys are left high as hanging valleys.
16 of 41

FEATURES OF COLD ENVIRONMENTS

FJORDS:

  • Glacial troughs below or partly below sea level
  • Up to one-quarter of fjords have active layers (the top layer of soil that thaws during the summer and freezes in winter)
  • Fjords are more likely to be U-shaped than land-based glacial troughs because most fjords are cut into resistant rock whereas land-based troughs are often covered with deposits of scree and soil.
  • Many fjords have a long profile which shows a greater degree of glacial erosion at the source of the fjord compared with the mouth.
  • Fjords deepen quickly near their source, then decline very gently towards the seaward end, 
  • The mouth of a fjord is often marked with a sill or threshold, an area of shallow rocky ground of moraine
  • This is thought to be due to a reduction in glacial erosional power. 
  • E.G = the Sogne Fjord in Norway has a maximum depth of over 1300m but the mouth is only 200m deep
  • In Scotland, at Loch Morar and Loch Marree, the sills have been raised above sea level by isostatic uplift (the rising of the land when the weight of a glacier has been removed as a result of deglaciation. 
17 of 41

FEATURES OF COLD ENVIRONMENTS

MELTWATER CHANNELS:

  • Water that comes from melting snow or ice.
  • Capable of intense erosion
  • Meltwater streams can carve deep meltwater channels in the land.
  • E.G. Next card
18 of 41

FEATURES OF COLD ENVIRONMENTS

E.G. OF MELTWATER CHANNELS - North York Moors area:

  • During the last glaciation, ice sheets up to 300m thick in some places, spread south and south-west from north England and the North Sea, surrounding the North York Moors area, leaving the moors as an island of uncovered ice-free land 
  • As the ice moved south, it first blocked the mouth of the River Esk and stopped its water from reachnig the North Sea 
  • At the same time, ice moving from the western edge of the moors blocked the alternative outlet.
  • Gradually water gathered in the low-lying dales, forming lakes that found temporary outlets across the ridges between one dale and another. 
  • Here the water cut cols or spillways (a low point in a ridge or high ground, often formed as a result of back-to-back cirques. Some may be formed by the movement of glacier ice from one valley into another and some by glacial diversion of drainage).
  • Eventually the lake waters joined and the water surface stood 215m above present sea level.
  • At this height, the water spilt over the lowest point of the main divide and began to flow southwards in an ever-increasing torrent, which eroded the trench at Newtondale - Newton dale is thus known as an overflow channel. 
  • This feature is a well-defined trench 75m deep with very steep sides cut into the surrounding plateau of the moors.
19 of 41

FEATURES RESULTING FROM GLACIAL DEPOSITION

ERRATICS:

  • Large boulders foreign to the local geology that ave been dumped by the ice usually of flat ares
  • Often left in precarious positions (not securely held or in position.
  • E.G. = Bluish micro-granite from an island off the Ayrshire coast has been found in the Merseyside area in Fishguard in Dyfed.

(http://4.bp.blogspot.com/-6ve1YyyvVUs/TpNSYR2ZrXI/AAAAAAAABH8/7i4CrwJjLhI/s1600/Lofoten+erratics.jpg)

20 of 41

FEATURES RESULTING FROM GLACIAL DEPOSITION

Till:

  • A common widespread nad unstratified glacial deposit composed of finely grained rock flour (sands and clays) mixed together with rocks of different shapes and sizes.
  • Composition is variable depending on the nature of the rock, over wihch th ice is moved
  • Divided into two types:

1) Lodgement till - dropped by actively moving glaicers. Sheared and smeared by the weight of overlying ice as it continues moving

2) Ablation till dropped by stagnant ice (coarser that lodgement till)

21 of 41

FEATURES RESULTING FROM GLACIAL DEPOSITION

MORAINES:

  • Lines of loose rock fragments which have been weathered from the valley sides above the ice and have fallen downslope onto the ice
  • The lines of material lying near the valley sides are lateral moraines
  • Where two glaciers meet, the lateral moraines of each will join to form medial moraine down the centre of the glacier
  • At the snout of a stationary glacier or slowly moving glacier, much material is deposited as a cresent shaped mound or terminal moraine.
  • Character of terminal moraine depends on: the amount of material carried by the ice, the rate of ice movement, the rate of ablation and thus the amount of meltwater (ablation = the removal of material such as ice, debris, from a glacier such as by melting, evaporation)
  • Smaller recessional moraines mark the site where the snout halted for brief periods of time during the retreat of the ice front
  • Debris is carried within the ice (englacial moraine) having made its way down crevasses and moulins within the ice
  • Debris is also found at the base of ice (subglacial moraine) this is left after ta steady retreat of the ice.

E.G.= the largest terminal moraine in Britain is in the Cromer Ridge in Norfolk - it forms a belt of hummockiy hills composed of sands and gravels 8km wide and 90m high.

22 of 41

FEATURES RESULTING FROM GLACIAL DEPOSITION

DRUMLINS:

23 of 41

FLUVIOGLACIAL DEPOSITS

PROLONGED DRIFT

ICE CONTACT STRATIFIED DRIFT

24 of 41

FLUVIOGLACIAL DEPOSITS

ESKERS

25 of 41

FLUVIOGLACIAL DEPOSITS

KAMES

26 of 41

PERIGLACIAL FEATURES

PATTERNED GROUND

27 of 41

PERIGLACIAL FEATURES

PINGOS

28 of 41

PERIGLACIAL FEATURES

ICE WEDGES AND ICE-WEDGE POLYGONS

29 of 41

RELICT (PAST) FEATURES

DRY VALLEYS

30 of 41

RELICT (PAST) FEATURES

MISFIT RIVERS

31 of 41

RELICT (PAST) FEATURES

LOESS

32 of 41

RELICT (PAST) FEATURES

SCREE SLOPES

33 of 41

FRAGILITY OF COLD ENVIRONMENTS

VEGETATION:


34 of 41

FRAGILITY OF COLD ENVIRONMENTS

ANIMALS

35 of 41

FRAGILITY OF COLD ENVIRONMENTS

SOILS:

36 of 41

FRAGILITY OF COLD ENVIRONMENTS

NUTRIENT CYCLE

37 of 41

FRAGILITY OF COLD ENVIRONMENTS

TUNDRA ECOSYSTEMS

38 of 41

DEVELOPMENT, CONFLICT AND MANAGEMENT

SKI TOURISM IN EUROPE

ISSUES WITH DEVELOPMENT 

MANAGING SUSTAINABLY

39 of 41

DEVELOPMENT, CONFLICT AND MANAGEMENT

OIL INDUSTRY IN ALASKA

CONFLICT

MANAGEMENT

40 of 41

DEVELOPMENT, CONFLICT AND MANAGEMENT

HIMALAYA - NEPAL

FRAGILITY = CONFLICT

ECONOMIC DEVELOPMENT + ISSUES WITH THIS

CONSERVATION AND SUSTAINABLE MANAGEMENT

41 of 41

Comments

Caitlin x

Could have been nice to have more detail on the later resources but otherwise really helpful!

Similar Geography resources:

See all Geography resources »See all Hot and cold environments resources »