Glacial Systems and Landscapes

• Fluvioglacial Processes of Erosion


  Hydraulic Action: Sheer force of the water.

  Abrasion: Stones in transport within the water are thrown at the bed and the banks.

  Solution: Weak acids within the water react with the rocks.

  Attrition: Rock fragments in transport are thrown into one another.
• Accumulation


  When inputs exceed outputs and the glacier advances. Inputs include; snow, ice and avalanches.

  
• Ablation


  When outputs exceed inputs and the glacier retreats. Outputs include; meltwater at the snout, sublimation (When anything solid turns into a gas without first becoming liquid), evaporation at the surface, calving where blocks of ice break off at a glacier's snout.

  
• Equilibrium Line


  The boundary between the accumulation zone and the ablation zone. If the glacier is in a state of balance where inputs equal outputs, the equilibrium line will remain in the same place.
• Positive Feedback


  A cooling in temperature causes ice to expand, and its surface increases in reflectivity. This means that less heat is absorbed by the surface of the ice, and the temperatures of the glacial ice decrease. This in turn allows for more ice formation
• Negative Feedback


  The Greenland Ice sheet starts to melt because of warmer temperatures. This causes freshwater to enter the North Atlantic. This desalinises (removes salt) the water, making it less dense. This could affect the North Atlantic Drift, reducing its effects and causing temps to drop by 2'C in N-W Europe.
• Pleistocene


  A geological period that began 2.6 million years ago and ended approximately 11,800 years ago and in which ice coverage was much greater than can be seen today. The present interglacial marks the end of the Pleistocene era.
• Last Glacial Maximum


  Occurred around 27,000 years ago, was the most recent time during the last glacial period that ice sheets were at their greatest extent.

  
• Factors affecting the location of Cold Environments (LAARD)


  Latitude: The higher the latitude, the less solar radiation.

  Altitude: The higher the altitude, the lower the temperature due to lower air density.

  Aspect: In the Northern Hemisphere, southern facing slopes receive more energy due to the movement of the sun throughout the day.

  Relief: If the slope is too steep, the snow and ice from precipitation may just slide down the peak, rather than accumulating.

  Distance from moisture source: Precipitation is more likely to occur near a moisture source, the sea or ocean, than in what are known as "continental interiors".
• Characteristics of Polar Environments


  Areas of permanent ice.

  Never above 10 degrees.

  Winters normally between -40 and -90 degrees.

  Precipitation is low with less than 100mm per year.

  Long winters and short summers.

  Most of the land is ice covered. Where there is ice free land, soils are thin and infertile. They lack nitrogen and carbon due to low rates of decomposition. The vegetation is therefore limited.

  Mostly mosses and lichens grow.

  
• Characteristics of Periglacial Environments


  Temperatures consistently below freezing for most of the year (between -40 and 18) and little precipitation (380mm or less).

  However there are clearly defined seasons (brief, mild summers and long, cold winters).

  Soil is thin, acidic and not very fertile. There is normally a permafrost layer, toped with a layer of soil that melts in the summer (active layer).

  Plants grow slowly and not very tall- grasses most common. Some short, small trees grown in warmer, sheltered areas.

  
• Characteristics of Glacial Environments


  Found at the edges of ice sheets and, in particular, in mountainous regions.

  Cold enough for ice to be present all year round.

  It may be warm enough in summer in lower altitudes for meltwater to form.

  There is no exposed soil. Few plants- mostly moss and algae that may grow on the glacier in some areas.

  
• Characteristics of Alpine Environments


  Mountainous areas.

  Winters are cold, but summers can be mild (averages -2 to 4 degrees)

  When ice melts in summer, soil is exposed in some areas. Higher up, land is permanently covered.

  Soil is very thin and gravel like. Low decomposition rates lead to the soil being very infertile. Low lying shrubs, mosses and alpine flowers can thrive.

  Coniferous trees at lower altitudes

  
• Adaptations of Vegetation- Coniferous Trees


  Green all year round to allow as much photosynthesis to take place as possible due to the very short growing season.

  The needles are dark in colour allowing them to absorb heat from the sun.

  They tend to be thin and grow close together to give them protection from the cold and the wind to reduce transpiration.

  Their triangular shape also allows for snow to fall off to protect them during harsher winters and the seeds are held within cones to protect against the cold temperatures.

  
• Adaptations of Vegetation- Arctic Moss


  Non-vascular plant, it has no roots and instead uses tiny threads to anchor itself to rocks exchanging carbon with the atmosphere to grow.

  They often anchor themselves in cracks in rocks where meltwater may be captured to provide the water needed to grow.

  It is very slow growing to suit the short growing season.

  When it is not growing, it stores nutrients so new leaves can be made quickly next spring. The more leaves the more they can photosynthesise.

  It is adapted to the incredibly strong winds because it grows near to the ground to reduce water loss during transpiration.

  
• Glacial Budget


  The balance between inputs and outputs during a year.
• Terminal Moraine


  A high ridge of sediment that is pushed ahead of the glacier. If the glacier is retreating, the terminal moraine is left abandoned.

  
• Positive impacts of changing glacial budgets


  Meltwater can be an invaluable water supply for local communities in summer months.

  Use of meltwater for HEP in summer months.
• Negative impacts of changing glacial budgets


  Long term problem -glacier will have a negative budget and retreat, therefore not providing melt water for local communities.

  Localised flooding of nearby settlements and destruction of infrastructure.

  Loss of glacier will impact alpine tourism opportunities (At low altitude resorts in Europe, snow depth is shrinking by 3-4cm every 10 years.)
• Causes of Ice Advance and Retreat- Milankovitch Cycles


  The Earth changing its orbit around the sun which occurs around every 100,000 years. The orbit can vary from circular to elliptical and this can affect the amount of solar energy received by the earth. Less energy will result in a growth of glaciers and more energy causes an interglacial as ice sheets melt.

  
• Causes of Ice Advance and Retreat- Sunspot Activity


  A sunspot is a dark patch that appears from time to time on the surface of the sun. The number increases and decreases over a period of about 11 years. This is called the sunspot cycle.

  When sunspot activity is at a maximum the sun gives off more heat.

  
• Causes of Ice Advance and Retreat- Volcanic Activity


  When SO₂ erupted from volcanoes mixes with water vapour, it becomes volcanic (sulphate) aerosol. Volcanic aerosols reflect the sunlight away and reduce the Sun's heat energy entering the Earth's atmosphere.

  This cooling can lead to increased snow precipitation and the growth of ice sheets and glaciers.

  
• Causes of Ice Advance and Retreat- Ocean Current Changes


  The ocean conveyor belt can be affected by changes to winds and changes in salinity (e.g. if more freshwater from melting glaciers enters the ocean, then this can reduce salinity and prevent the cooler, denser water sinking affecting the movement).

  Similarly, during interglacials, the conveyor belt operates more effectively again and transfers warm water to polar areas, melting sea ice.

  
• Pressure Melting Point


  The point at which the glacier will start melting at the ground surface.

  
• Characteristics of Warm Based Glaciers


  Found in temperate environments.

  Mid latitudes.

  Greater ranges in temperature.

  More movement and erosion. (3 metres per day)

  There is surface melting in the summer.

  At the base, the temperature reaches PMP and meltwater will be produced.

  Moves by basal sliding and internal deformation.

  
• Characteristics of Cold Based Glaciers


  Found in polar environments.

  High latitude.

  Temperature of the ice remains below zero all year.

  Little movement (1-2 cm per day)

  Little erosion.

  There is no surface melting.

  Despite an increase in temperature with depth, it never reaches PMP and therefore the ice remains frozen at the base.

  Moves by internal deformation.

  
• Geomorphological Processes


  Natural processes that result in modification on the earth's surface. Most active at the margins of cold environments where precipitation amounts are higher and warmer summers leads to the creation of meltwater.
• Geomorphological Processes- Weathering (frost action or shattering)


  Water (rainwater or meltwater) seeps into cracks and pores of the rock. When the temperature falls below 0°C, the water turns to ice and expands. This enlarges any cracks.

  This process repeats, until the cracks become so large that chunks of rock break off.

  
• Geomorphological Processes- Nivation


  This is the effect of snow on a landscape.

  When snow patches accumulate on a slope, weathering can cause the underlying rock to disintegrate.

  Meltwater in the summer will then carry away weathered rock debris.

  Nivation is the result of a mixture of both frost action and abrasion.

  
• Impact of geomorphological processes on the landscape- Scree


  Tiny bits material created by frost action. A scree slope is where the material collects at the foot of a slope. Material picked up by glaciers and used as an abrasive tool

  
• Impact of geomorphological processes on the landscape- Blockfield


  Extensive areas of flat land or gentle slopes where there is an accumulation of large angular boulders which have been created by regular frost action

  
• Impact of geomorphological processes on the landscape- Frost Heave


  Rainwater that is freezing just below the surface of the soil expands and pushes up the ground above. The growth of ice crystals can raise individual soil particles.

  
• Impact of geomorphological processes on the landscape- Nivation Hollow


  Snow patches accumulate in small depressions protected by the wind.

  Weathering by frost action can cause the underlying rock to disintegrate.

  Meltwater in the summer will carry away the weathered rock debris to reveal an ever-enlarging nivation hollow.

  Slumping may also take place in the summer

  
• Ice Movement- Internal Deformation


  Occurs when the weight of the ice causes the deformation of ice crystals and takes place in both warm and cold based glaciers. There are two types; intergranual and intragranular movement.
• Ice Movement- Basal Sliding


  When the presence of meltwater (in warm based glaciers) lubricates the base of the ice.
• Regelation


  The process of melting and freezing due to pressure.
• Variations in Ice Movement- Extensional flow


  Where there is a sudden increase in the gradient, the ice will flow faster, and through internal deformation, the ice will become stretched and will thin.

  
• Variations in Ice Movement- Compressional Flow


  A reduction in gradient will cause the glacier to slow down causing it to pile up and become thicker.

  
• Variations in Ice Movement- Rotational Flow


  This usually happens in a hollow (such as a nivation hollow). Here, as the ice moves downhill it pivots around a point. This can lead to deepening of the hollow.
• Active Layer


  During the brief and potentially quite warm summers, lying snow melts, as will the upper portion of permafrost making it saturated.