Glacial Systems

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  • Glacial Systems
    • Types of Glaciers
      • Mountain Glaciers
        • Develop in high mountainous regions
        • Largest found in Arctic Canada, Alaska, Andes in S America & Himalayas in Asia
      • Hanging Glaciers
        • When a major valley glacier system retreats and thins, sometimes the tributary glaciers are left in smaller valleys high above the shrunken central glacier surface
        • Called 'Hanging Valleys' if the entire system has melted and disappeared.
      • Valley Glaciers
        • Originating from mountain glaciers or icefields
        • Spill down valleys
        • Very long, often flowing down beyond the snow line, sometimes reaching sea level.
      • Tidewater Glaciers
        • Valley glaciers that reach the sea.
        • Responsible for calving small icebergs
      • Piedmont Glaciers
        • Occur when steep valley glaciers spill into flat plains and spread out.
        • Largest in world: Malaspina Glacier in Alaska
      • Cirque Glaciers
        • Found high on mountainsides
        • Tend to be wide rather than long
      • Rock Glaciers
        • Form when slow-moving glacial ice is covered by debris
        • Found in steep-sided valleys, where rocks and soil fall from the valley walls onto the ice.
        • May also form when frozen ground creeps downslope
      • Ice Aprons
        • Small, steep glaciers that cling to mountainsides
        • Often wider than they are long.
        • Common in Alps and New Zealand
        • Often cause avalanches due to the steep inclines they occupy.
      • Ice Shelves
        • Occur when ice sheets extend over the sea and float on water.
        • Range from a few hundred metres to 1+ km in thickness
        • Surround most of Antarctic continent.
      • Ice Fields
        • Flow is influenced by underlying topography
        • Typically smaller than ice caps
      • Ice Caps
        • Miniature ice sheets, covering less than 50 000 km^2
        • Form primarily in polar and sub-polar regions that are relatively flat and high in elevation
      • Ice Streams
        • Large ribbon-like glaciers set within an ice sheet
        • Bordered by ice flowing more slowly, rather than rock or mountain ranges.
        • Very sensitive to changes (e.g. loss of ice shelves, changing amounts of water flowing beneath them).
        • Antarctic ice sheet has many ice streams
      • Ice Sheets
        • Found only in Antarctica and Greenland
          • Antarctica ice sheet = 4.7+ km thick
        • Enormous continental masses of glacial ice and snow, expanding over 50,000km^2
    • Outputs
      • Meltwater
      • Deposit debris/rock fragments
      • Water Vapour
      • Calving
    • Inputs
      • Precipitation
      • Debris
      • Avalanches
    • Ice Mass Balance
      • Gain and loss of ice from the glacier system
      • Glaciers losing more mass than they receive will be in negative mass balance and recede.
      • Glaciers gaining more mass than they lose will be in positive mass balance and will advance.
      • Glaciers gaining and losing approx. the same amount of snow and ice are 'in equilibrium'. They will neither advance or recede.
      • In the upper part of the glacier, where inputs exceed outputs and where more mass is gained than lost over a year, is known as the zone of accumulation.
      • In the lower part of the glacier, where outputs exceed inputs and where more mass is lost rather than gained, is known as the zone of ablation.
    • Formation
      • 1. Form when snow remains in the same area year-round. Enough snow accumulates to form ice.
      • 2. Each year, new layers of snow bury and compress previous layers.
      • 3. Compression forces snow to recrystallise
      • 4. Grains grow larger and the air pockets between them get smaller, causing snow to slowly compact and increase in density.
      • 5. Snow turns to firn after approx. 2 winters.
      • 6. Over time, larger ice crystals become so compressed that any air pockets between them are very tiny.
  • Feedback
    • Positive
      • Ice-albedo feedback
      • 1. Increase in temp.
      • 2. Ice melts
      • 3. Darker surfaces revealed
      • 4. Albedo reduced
      • 5. Increased absorption of solar respiration.
    • Negative
      • 1. Earth cools
      • 2. More ice forms
      • 3. Increases albedo
      • 4. Reduced amount of energy absorbed.
    • Glacial Systems
      • Types of Glaciers
        • Mountain Glaciers
          • Develop in high mountainous regions
          • Largest found in Arctic Canada, Alaska, Andes in S America & Himalayas in Asia
        • Hanging Glaciers
          • When a major valley glacier system retreats and thins, sometimes the tributary glaciers are left in smaller valleys high above the shrunken central glacier surface
          • Called 'Hanging Valleys' if the entire system has melted and disappeared.
        • Valley Glaciers
          • Originating from mountain glaciers or icefields
          • Spill down valleys
          • Very long, often flowing down beyond the snow line, sometimes reaching sea level.
        • Tidewater Glaciers
          • Valley glaciers that reach the sea.
          • Responsible for calving small icebergs
        • Piedmont Glaciers
          • Occur when steep valley glaciers spill into flat plains and spread out.
          • Largest in world: Malaspina Glacier in Alaska
        • Cirque Glaciers
          • Found high on mountainsides
          • Tend to be wide rather than long
        • Rock Glaciers
          • Form when slow-moving glacial ice is covered by debris
          • Found in steep-sided valleys, where rocks and soil fall from the valley walls onto the ice.
          • May also form when frozen ground creeps downslope
        • Ice Aprons
          • Small, steep glaciers that cling to mountainsides
          • Often wider than they are long.
          • Common in Alps and New Zealand
          • Often cause avalanches due to the steep inclines they occupy.
        • Ice Shelves
          • Occur when ice sheets extend over the sea and float on water.
          • Range from a few hundred metres to 1+ km in thickness
          • Surround most of Antarctic continent.
        • Ice Fields
          • Flow is influenced by underlying topography
          • Typically smaller than ice caps
        • Ice Caps
          • Miniature ice sheets, covering less than 50 000 km^2
          • Form primarily in polar and sub-polar regions that are relatively flat and high in elevation
        • Ice Streams
          • Large ribbon-like glaciers set within an ice sheet
          • Bordered by ice flowing more slowly, rather than rock or mountain ranges.
          • Very sensitive to changes (e.g. loss of ice shelves, changing amounts of water flowing beneath them).
          • Antarctic ice sheet has many ice streams
        • Ice Sheets
          • Found only in Antarctica and Greenland
            • Antarctica ice sheet = 4.7+ km thick
          • Enormous continental masses of glacial ice and snow, expanding over 50,000km^2
      • Outputs
        • Meltwater
        • Deposit debris/rock fragments
        • Water Vapour
        • Calving
      • Inputs
        • Precipitation
        • Debris
        • Avalanches
      • Ice Mass Balance
        • Gain and loss of ice from the glacier system
        • Glaciers losing more mass than they receive will be in negative mass balance and recede.
        • Glaciers gaining more mass than they lose will be in positive mass balance and will advance.
        • Glaciers gaining and losing approx. the same amount of snow and ice are 'in equilibrium'. They will neither advance or recede.
        • In the upper part of the glacier, where inputs exceed outputs and where more mass is gained than lost over a year, is known as the zone of accumulation.
        • In the lower part of the glacier, where outputs exceed inputs and where more mass is lost rather than gained, is known as the zone of ablation.
      • Formation
        • 1. Form when snow remains in the same area year-round. Enough snow accumulates to form ice.
        • 2. Each year, new layers of snow bury and compress previous layers.
        • 3. Compression forces snow to recrystallise
        • 4. Grains grow larger and the air pockets between them get smaller, causing snow to slowly compact and increase in density.
        • 5. Snow turns to firn after approx. 2 winters.
        • 6. Over time, larger ice crystals become so compressed that any air pockets between them are very tiny.

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