Cold Environments: A Summary

Glacial Environments are ones that are defined as having snow and ice all year round with a greater net negative degree days (varying between -60 Degrees Celsius to -10 Degrees Celsius). Katabatic winds also flow downwards from mountains to lowland, cooling the ground. E.g. Northern Norway, Sweden, Siberia

Mountain (alpine) climates are ones that were once covered in ice and are now free. Some contain glaciers and ice caps such as with the Himalayas and the Alps. They lose 1 degree celsius for every 100m in altitude. Orographic rainfall is also produced in these areas as air is forced to rise over high ground causing it to cool and condense and eventually precipitate.

Periglacial environments are ones where snow and ice is present, just not all year round. They are effectively areas on the ‘edge’ of glaciers. They occur in areas of high altitude (temperature declines) or latitude (low insolation as the angle of overhead sun is reduced). High albedo – sun rays reflected by the snow. (absorption rates average = 40%, dark soils = 90% and snow = 10-20%). Areas also have low precipitation (less than 160 mm), low air temperatures and high pressure. They have a relatively wide temperature range from an average of -50 degrees celsius in winter to +16 degrees celsius in summer. Examples of these types of environment include lower Siberia and the Mackenzie Delta in Canada which has a number of periglacial features such as patterned ground.

Glacier Formation

Glaciers are formed during prolonged periods of cold conditions and snowfall. They are often formed on the North Eastern facing sides of mountains, snow is able to accumulate here without wind sweeping it away. Snow accumulates and compacts, becoming granular in consistency (known as firn or neve) this forms a nirvation hollow in the side of the mountain. As the snow continues to accumulate it begins to drag downwards when it reaches its critical mass. Traits found within a glacier include crevasses – cracks in a glacier caused by constant movement over obstacles and randklufts – a gap between the rock surface and ice caused when head from the rock melts the ice. The zone of accumulation is the area of positive net balance and the zone of ablation is the area of negative net balance (often where fluvioglacial deposits occur). Glacial accumulation occurs when there are fewer positive degree days than negative in Summer and ablation occurs in the opposite circumstance. E.g. Alaska Coast Range.

Glacier Vocabulary:

Entrainment: material from the glacier’s bed is embedded into the moving ice

Permafrost terms

  • Continuous: permanently frozen soil, deposits or ground (Northern Canada/Siberia)
  • Discontinuous: where mean annual air temperatures are between -6 and -1 degrees celsius, often more fragmented and thinner than continuous
  • Active layer: top layer of the ground above permafrost that endures seasonal freezing and thawing

Glacial Processes:

  • Extrusion Flow: movement of ice as a result of becoming too deep or heavy and becomes unstable – ‘collapses’ and flows outwards over own weight and pressure
  • Basal sliding: movement of ice of warm-based glaciers (glaciers that are not frozen to the rock surface) where water acts as a lubricant. It often occurs on steep slopes in summer.
  • Surging: periodic collapse of a glacier mass when it reaches critical level in the accumulation zone – movement is between 10 – 100 times faster.
Glacial Erosion
  • Plucking: ripping out of material from bedrock. Occurs mainly at the base of glacier and the sides. Moves downward due to pressure caused by its own weight, this downhill drag leads to abrasion.
  • Abrasion: material that is carried by the glacier is dragged over the bedrock forming striations (continuous lines of erosion) and chatter marks (discontinuous lines of erosion)
  • Freeze-thaw weathering: infiltration of water into cracks in rocks expands when frozen forms ice wedges. A relic feature of ice wedging is Long Hanborough Carrot in Oxfordshire
Features of Glacial Erosion:
U-Shaped Valleys:
  • Previously V-shaped valleys that have been carved by glacial movement creating truncated spurs (land interjections that have been cut off by the glacial erosion)
  • Contain misfit rivers (rivers too small to have caused erosion of the valley) and ribbon lakes
  • E.g. Nant Ffrancon Valley, Wales
Hanging Valleys:
  • Small U-shaped valley formed by a glacier that joins and hangs above a large U-shaped valley formed by a larger glacier
  • Often the site of waterfalls
Cirques (AKA Cwm or a Corrie):
  • Armchair shaped hollow with knife-edged shaped ridges (aretes) – formed by back to back cirques
  • When free of glacier ice form tarn lakes
  • Deepened by glacial rotational movement
  • E.g. Western Cwm and Cwm Idwal, Snowdonia
Features of Glacial Deposition:
Moraines:
  • Lines of weathered loose, unstratified rock fragments from valley sides above the ice
  • Lateral: material lying near valley sides parallel to glacier flow
  • Medial: away from valley sides at confluence of separate glaciers meeting point
  • End: at the snout of stationary/slow glacier – crescent shaped
  • E.g. Gorner Glacier, Switzerland
Erratics:
  • Large rocks deposited at low energy in environment foreign to their origin (evident by different bed rock)
  • ‘Plucked’ from original bedrock and embedded and transported in the glacier
  • E.g. Madison Boulder, New Hampshire, USA
Drumlins:
  • Streamlined mound of till
  • Smooth and elongated
  • Occurs when ice hits an obstacle causing a slow down in movement, active glacier ice deposits till
  • 5-50 metres high
  • 10-3,000 metres long
  • Occur in swarms
  • E.g. Carrick, West County Meath, Ireland
Outwash Plains:
  • Deposited by meltwater from the glacier
  • Gently sloping surface made of rounded and stratified sands and gravel
  • The smaller the particles the further they are from the glacial margin
  • Vary in size
  • E.g. Terminus Peyto Glacier, Banff National Park, Canada
Periglacial Processes:
  • Frost Heave (AKA Congeliturbation): Water freezes in soil, pushes and churns surface upwards (forms patterned ground)
  • Frost Shattering (AKA Congelifraction, Gelifraction): Splitting of rocks by freeze-thaw action (expansion and contraction)
  • Ice Lensing: formation of ice crystals in soil
  • Solifluction (a slope process): soil creep, particles pushed up by ice freezing at a 90 degree angle and move downwards during thawing
Chemical Weathering Occurring in Glacial and Periglacial Environments:
  • Carbonation: increased at lower temperatures as CO2 solubility is increased, streams lower in pH and weathering in rocks increases
  • Vegetation rot (occurs in periglacial) creates organic acids that cause weathering
  • Hydrolysis: presence of organic acids react to form clay minerals
Features of Periglacial Environments:
Patterned Ground:
  • Formed by frost heave – stones are moved to the surface
  • Come in the forms of:
  • Circles
    Nets
    Polygons
    Steps
    Stripes – e.g. Tinto Hill, Scotland
Pingos:
  • Isolated conical hills formed when water freezes and expands
  • 30-600 metres in diametre
  • 3-70 metres in height
  • Form in permafrost environment
  • E.g. Mackenzie Delta, Canada
  • Open system: form from groundwater flowing from an outside source
  • Closed system: form from isolation and progressive infill of a small lake (talik)
Erosional Fluvioglacial Features:
  • Meltwater Channels: carved by meltwater streams from glacier ice
  • Form cols or spillway – a low point in ridge/high ground formed by back to back cirques (arete)
  • E.g. North York Moors
Depositional Fluvioglacial Features:
Ice Contact Stratified Drift:
  • Stratified sand and gravel sorted by meltwater streams
  • Deposited next to glacier
  • Modified by ice retreat
Kames:
  • Irregular mounds of bedded unstratified sand and gravels
  • Also accompanied with kettle hole lakes as ice melts (‘Kame and Kettle country’)
  • Kame terraces: found on ice edge, formed by streams)
  • E.g. Boyne Valley, Ireland
Eskers:
  • Created by subglacial meltwater
  • Sand and gravel ridges deposited by meltwater flowed in channels beneath and inside the ice
  • E.g. Munroe Esker, Canada (400 Km long!)
Relic Features:
Dry Valleys:
  • River valleys without rivers
  • Often made of chalk and limestone that is impermeable during glacial periods, however, when temperature rises, permeability returns and water sinks into the rocks and are left dry
  • E.g. Devil’s Dyke, Brighton
Misfit Rivers:
  • Small rivers occupying large valleys
  • Caused by rapid runoff from snowmelt that carves the steep valleys
  • E.g. River Windrush, Cotswolds
Scree Slopes:
  • Large quantities of angular fragments at angle of rest
  • E.g. Wastwater, Lake District
Loess:
  • Unstratified silt and angular/sub-angular pieces laid down by wind
  • Found in Northern Europe

Charlotte Tidman

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