Glaciers

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Glaciers
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Take-Away Points

• Glaciers are flowing streams of ice
• Glaciers have a zone of accumulation where
  snowfall exceeds losses (ablation)
• Accumulation can be due to high altitude
  (mountain glaciers) or cold climate (continental
  glaciers)
• Glaciers have a zone of ablation where losses
  exceed snowfall
• Glaciers are governed by a balance of snowfall,
  ice flow, and ablation
• Glaciers retreat by melting back, not by
  retracting
• Glaciers produce distinctive landforms and small
  scale features

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Glacier a Flowing Stream of Ice

• Mountain
• Continental (Greenland, Antarctica)

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Snowfall vs Melting Evaporation (Ablation)

• Zone of Accumulation
• Snowfall Exceeds Melting Evaporation
• Excess Snow Turns to Ice Flows Out
• Zone of Melting or Ablation
• Melting Evaporation Exceeds Snowfall
• Melting Excess Made up by Ice Flowing in
• Terminus of Glacier
• Snowfall Inflow Melting Evaporation
  (Ablation)

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Anatomy of a Glacier
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A Typical Glacial Advance and Retreat
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As long as Accumulation Ablation, the Glacier
Front Remains Fixed
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If Accumulation Exceeds Ablation, the Glacier
Advances
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If Ablation Exceeds Accumulation, the Glacier
Retreats
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Eventually, Material Trapped in the Ice Reaches
the Terminus
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A Typical Glacial Advance and Retreat
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Results of Glaciation

• Abrasion
• Polish
• Striations
• Chatter Marks
• Crescentic Gouges
• Bedrock Scour

• Deposition
• Till
• Outwash
• Varved Clays
• Meltwater Erosion

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Mountain Glacier Landforms
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Continental Glacier Landforms
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Greenland Ice Cap
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Antarctic Ice Cap
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Antarctic Subglacial Lakes
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Lake Vostok
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Take-Away Points

• Glaciers are flowing streams of ice
• Glaciers have a zone of accumulation where
  snowfall exceeds losses (ablation)
• Accumulation can be due to high altitude
  (mountain glaciers) or cold climate (continental
  glaciers)
• Glaciers have a zone of ablation where losses
  exceed snowfall
• Glaciers are governed by a balance of snowfall,
  ice flow, and ablation
• Glaciers retreat by melting back, not by
  retracting
• Glaciers produce distinctive landforms and small
  scale features