The glacier system

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A-Levels Glaciation Mind Map on The glacier system, created by EmmaSmile on 05/05/2013.
EmmaSmile
Mind Map by EmmaSmile, updated more than 1 year ago
EmmaSmile
Created by EmmaSmile over 11 years ago
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The glacier system
  1. As climate deteriorates and becomes colder more precipitation in winter falls as snow and summers are shorter, leaving less time for snow to melt. May be permanent snow cover in upland areas.
    1. Lower edge of area of permanent snow cover is known as the snow line. The snow line will be further down slope as climate becomes colder.
      1. In Greenland snow line is at sea level. In Northern Hemisphere the snow line found higher on south facing slopes as south facing sloes recieve more radiation from sun.
    2. Formation of Ice
      1. Ice is derived from compacted snow (also some sleet, hail, rain which freezes on top/inside glacier)
        1. As climate gets colder more snow - permanent snow line forms as snow accumulates on ground
          1. Formation of permanent snow field first stage in formation of glacier (at high altitudes in mountains or high latitudes where winter accumulation exceeds summer snow melt)
            1. Snow falls - traps air, low density 0.1gcm3
              1. Snow accumulates layer on layer - compaction. Each new layer compresses below, forces air out converting to ice - diagenesis
                1. Snow experiencing a winter's accumulation and survives summer melting is compacted to density of 0.5gcm3 and is known as neve. Increased density due to increased pressure. Some melting within snow, water re-freezes and fills gap between individual ice crystals.
                  1. Over time with increasing depth, density increases forming glacial ice - density 0.9cm3 (colder climate - longer to form glacial ice as meltwater speeds up process). Where wet snow, e.g. Alaska - glacial ice within 5 years. Antarctica 150-200 years.
                    1. Overlying weight increases- glacial ice deforms, moves outwards to area of lower pressure downhill and moves - glacier.
      2. Summary of the glacial system
        1. Inputs
          1. Energy (solar and kinetic)
            1. Precipitation
              1. Moraine
              2. Processes/transfers
                1. Ice movement
                  1. Erosion (abrasion/plucking)
                    1. Transportation
                      1. Deposition
                      2. Outputs
                        1. Ablation (melting)
                          1. Sediment
                            1. Calving (breaking off of chunks of ice at end of glacier)
                          2. Change in position of a glacier over a year - advance and retreat
                            1. Glacier system constantly adjusts to change in balance between accumulation and ablation - known as mass balance
                              1. Accumulation - net gain in an ice mass, dominant in upper parts of glacier (accumulation zone) Inputs leading to accumulation - snow, refreezing of meltwater, avalanches, rockfalls
                                1. Ablation- net loss of water, dominant in lower parts of glacier - ablation zone. Higher annual temperatures. Outputs include melting (formation of meltwater streams), calving. evaporation and sublimation (ice straight to gas without turning into liquid)
                                  1. Over the course of a year glaciers expand and contract as mass balance differs according to season. Whether a glacier advances or retreats depends on average mass balance over year: annual budget or net balance.
                                    1. The balance year for calculating: time taken from minimum mass of one year to minimum mass next year (autumn to autumn - end of summer ablation)
                                      1. Positive mass balance is where accumulation> ablation. Net gain of ice normally case in winter, glacier advances.
                                        1. Negative mass balance: ablation> accumulation Normally case in spring and summer
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