Geography

• Terminal moraines


  High mound of till extending across a glacial trough, usually steeper on the up-valley side and tending to be crescent shaped.

  
  

  Marks maximum advance of the ice sheet - middle further due to less drag
• Lateral moraines


  Ridges of till running along the edge of a glacial trough.

  
  

  Derived from frost shattering of the valley sides
• Recessional moraines


  A series of ridges running across a glacial trough, lying broadly parallel to each other and to the terminal moraine.

  
  

  Marks an interruption in the retreat of the glacier
• Explanation of Terminal moraines


  They mark the position of the maximum advance of the ice and were deposited at the glacier snout. Their crescent shape is due to the position of the snout, further advance having occurred in the centre of the glacier than at the edges.
• Explanation of Lateral moraines


  Material accumulates on top of a glacier, having been weathered from the exposed valley sides. As the glacier melts, this material sinks through the ice to the ground and is deposited.
• Explanation of Recessional moraines


  They form during a temporary standstill in retreat as material carried to the snout of the glacier is deposited across the width of the trough.
• Moraine


  Landforms created when the debris carried by a glacier is deposited
• Glacial troughs


  Erosional landform

  
  

  Glacial troughs, also called U-shaped valleys, develop where glaciers flow into pre-existing V-shaped river valleys due to gravity and erode valley by abrasion and plucking

  
  

  Glaciers widen and deepen and straighten the original valley making it steep sided with a wide, flat base

  
  

  The mass of the ice has more erosive power than the river which originally cut the valley.

  
  

  Glaciers tend to straighten the valley, cutting off spurs and leaving cliffs called truncated spurs

  
  

  At the upper end of the valley where the glacier has entered the valley from the corries above, there is often a steep wall called the glacial trough.

  
  

  Called parabolic due to the weathering and mass movement of the upper part of the valley sides that goes on both during the glacial period and in the subsequent periglacial period as the glacier retreats. The resultant scree slopes that accumulate at the base of the valley sides lessen the slope angle

  
  

  
  

  There are often variations in the long profile of glacial troughs. When compressing flow occurs, the valley is over-deepened to form rock basins and rock steps. This process may be particularly evident where there are alternating bands of rock of different resistances on the valley floor - the weaker rocks being eroded more rapidly to form the basins.
• Corrie's description


  Armchair shaped hollows

  
  

  Found on upland hills or mountainsides.

  
  

  Steep back wall and over deepened basin and often lip at the front of solid rock or morainic deposits.
• Arêtes


  Narrowed steep sided ridges

  
  

  Found between two corries

  
  

  The ridge is so narrow that it's described as knifed edged
• Pyramidal peaks


  A steep sided peak between three or more corries

  
  

  Sharpened by freeze thaw weathering
• Troughs


  U shapes valleys with relatively straight platforms
• roche moutonnee


  Asymmetrical projections of resistant rock found on the floor of glacial troughs
• Striations


  Long parallel scars in rocks carved by rock fragments being dragged across them by a glacier (erosional)
• Ellipsoidal basins


  Large shallow basins

  
  

  With platforms similar to an ellipse
• Erratics


  Individual pieces of rock

  Varying in size

  Composed of a different geology to the area in which they are found
• Drumlins


  Asymmetrical elongated hills composed of glacial till

  
  

  The higher and wider stows or blunt end faces the ice flow while the lee side is more gently tapered
• Till sheets


  Large, thick masses of unstratified till forming extensive and relatively flat surfaces.
• 2.1 How can glaciated landscapes be viewed as systems?

  Key idea ⮕ Glaciated landscapes can be viewed as systems.

  
  

  System - set of interrelated objects compromising of stores and processes connecting together to form a working unit
• What do glaciers store and transfer?

  Energy and material
• Energy types in a glaciated system?

  Kinetic

  Potential

  Thermal

  GPE

  Geothermal - warms base
• The components of open systems

  -Inputs

  -Outputs

  -Throughputs
• Inputs (The components of open systems)

  Including kinetic energy - wind and moving glaciers,

  thermal energy from the heat of the Sun

  potential energy from the position of material on slopes

  material from deposition

  weathering and mass movement from slopes and ice from accumulated snowfall.

  Freeze thaw weathering - addition of debris
• Outputs (The components of open systems)

  Including glacial and wind erosion from rock surfaces;

  evaporation,

  sublimation

  meltwater.
• Throughputs (The components of open systems)

  Which consist of stores, including ice, water and debris accumulations; and flows (transfers), including the movement of ice, water and debris downslope under gravity.
• Stores

  Ice

  Water

  Debris
• Open system theory vs Glacial system


  Page 39.
• Glacier mass balance (Diagram)

  
• Glacier mass balance


  The glacier mass balance, or budget, is the difference between the amount of snow and ice accumulation and the amount of ablation occurring in a glacier over a one year time period.

  The majority of inputs occur towards the upper reaches of the glacier and this area, where accumulation exceeds ablation, is called the accumulation zone.

  
  

  Most of the outputs occur at lower levels where ablation exceeds accumulation, in the ablation zone. The two zones are notionally divided by the equilibrium line where there is a balance between accumulation and ablation.
• Ablation / Ablation zone

  LOW

  Refers to the low-altitude area of a glacier or ice sheet

  with a net loss in ice mass due to melting, sublimation, evaporation, ice calving, aeolian processes like blowing snow, avalanche, and any other ablation.
• Accumulation / Accumulation zone

  HIGH

  Occurs through accumulation of snow and other frozen precipitation, as well as through other means including rime ice, avalanching from hanging glaciers on cliffs and mountainsides above, and re-freezing of glacier meltwater as superimposed ice.

  Some areas - volcanic ash
• Sublimation


  The transition of a substance directly from the solid to the gas state, without passing through the liquid state.

  
  

  Solid - gas - latent energy
• Climate and glaciers


  Wind is a moving force and as such is able to carry out erosion, transportation and deposition.

  These aeolian processes contribute to the shaping of glaciated landscapes, particularly acting upon fine material previously deposited by ice or meltwater.

  
  

  Precipitation is a key factor in determining the mass balance of a glacier, as it provides the main input of snow, sleet and rain. (See page 41)

  
  

  Climate shapes the landscape
• Geology and glaciers


  The two key aspects of geology that influence glaciated landscape systems are lithology and structure.
• Lithology (Geology and glaciers)

  Describes the physical and chemical composition of rocks.

  Including colour, composition and texture

  
  

  Some rock types, such as clay, have a weak lithology, with little resistance to erosion, weathering and mass movements, as the bonds between the particles that make up the rock are quite weak.

  Others, such as basalt, made of dense interlocking crystals, are highly resistant and are more likely to form prominent glacial landforms such as arêtes and pyramidal peaks.

  Others, such as limestone, are predominantly composed of calcium carbonate. This is soluble in weak acids and so is vulnerable to decay by the chemical weathering process of carbonation, especially at low temperatures.
• Structure (Geology and glaciers)

  Concerns the properties of individual rock types such as jointing, bedding and faulting.

  It also includes the permeability of rocks.

  In porous rocks, such as chalk, tiny air spaces (pores) separate the mineral particles.

  These pores can absorb and store water - a property known as primary permeability.

  
  

  Carboniferous limestone is also permeable, but for a different reason. Water seeps into limestone because of its many joints.

  This is known as secondary permeability.

  The joints are easily enlarged by solution.

  Structure also includes the angle of dip of rocks and can have a strong influence on valley side profiles. Horizontally bedded strata support steep cliffs with near vertical profiles. Where strata incline, profiles tend to follow the angle of dip of the bedding planes.
• Geology vs lithology


  Geology - Study of rocks and minerals - structure of an area

  All the characteristics of the land including lithology

  
  

  Lithology - description of the physical characteristics of a rock unit or rock formation
• Relief, aspect and glaciers

  Latitude and altitude are the major controls on climate, however, relief and aspect have an impact on microclimate and the movement of glaciers.

  
  

  The steeper the relief of the landscape, the greater the resultant force of gravity and the more energy a glacier will have to move downslope. Where air temperature is close to 0ºC, it can have a significant influence on the melting of snow and ice and the behaviour of glacier systems.
• The formation of glacier ice

  Forms when temperatures are low enough for snow that falls in one year to remain frozen throughout the year. Fresh snow falls on top of the previous year's snow. Fresh snow consists of flakes with an open, feathery structure and a low density of about 0.05 g/cm³ (grams per cubic centimetre).

  
  

  Each new fall of snow compresses and compacts the layer beneath, causing the air to be expelled and converting low density snow into higher density ice.
• Valley glaciers


  Valley glaciers are confined by valley sides. They may be outlet glaciers from ice sheets or fed by snow and ice from one or more corrie glaciers. They follow the course of existing river valleys or corridors of lower ground. They are typically between 10 and 30 km in length, although in the Karakoram Mountains of Pakistan they are as long as 60 km.