Glaciers and Glacial Landforms

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Glaciers and Glacial Landforms
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Glacier - Mass of ice that persists throughout
the year.

• Accumulation and compaction of snow into ice.
• Ice deforms and flows outward responding to
  gravity.
• Flow generally from high to low altitude or high
  to low latitude.
• Ice advance stops where melting equilibrates with
  flow.
• Retreat by melting.
• Alpine glaciers - ice fills and flows down
  valleys.
• Ice caps - ice covers mountain peaks.
• Ice sheets - ice covers most of continent.

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Ice movement in a glacier
Snow falls
Ice melts
eroded boulders
Zone of accumulation
Zone of wasting
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Ice movement in a glacier
Snow falls
compacts to ice
Ice melts
Zone of accumulation
Zone of wasting
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Ice movement in a glacier

• If rate of accumulation is greater than melting,
  glacier will advance.

Snow falls
compacts to ice
Ice melts
Ice flows
Flowing ice carves the landscape
Zone of accumulation
Zone of wasting
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Ice movement in a glacier

• When rate of melting equals rate of accumulation,
  glacier stops advancing.
• Equilibrium

Snow falls
Glacier stops advancing.
Ice melts
Ice flows
Zone of accumulation
Zone of wasting
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• Ice movement in a glacier
• in equilibrium, glacier does not appear to change
  position.
• ice is always in motion.
• ice accumulation equals ice melting.

Glacier acts like a conveyor belt, eroding and
carrying rock, sediments, and soil to its
terminus.
Snow falls
terminus
Zone of accumulation
Zone of wasting
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• Ice movement in a glacier
• If melting increases, glacier will retreat, even
  though ice is still flowing.
• Rate of melting is greater than rate of
  accumulation.

Melting ice deposits rock and sediment. Glacial
deposits create distinctive landforms.
Snow falls
moraine
Ice flows
Zone of accumulation
Zone of wasting
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• Ice movement in a glacier
• If melting increases, glacier will retreat, even
  though ice is still flowing.
• Rate of melting is greater than rate of
  accumulation.

Melting ice deposits rock and sediment. Glacial
deposits create distinctive landforms.
Snow falls
moraine
Ice flows
Zone of accumulation
Zone of wasting
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Zone of ablation (wastage) (more melting than
snowfall)
Zone of accumulation (more snow falls then melts
per year)
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Glaciers - agents of erosion

• Glaciers are highly effective agents of erosion.
• Abrasion - rock debris embedded in base of ice.
• Polishing, grooves and striations.
• Plucking / Quarrying - removal of large chunks of
  rock debris.

Bedrock surface polished by glacial ice.
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Glaciers - Erosional Landforms

• Cirque - semicircular hollow with steep headwall
  carved by glaciers into an alpine valley head.

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Glaciers - Erosional Landforms

• Arete - steep, knife-edge ridge between glacial
  valleys.
• Col - gap in an arete where two cirques meet.
• Horn - steep peak carved out by cirques.

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Glaciers - Erosional Landforms

• Glacial trough - wide, parabolic valley carved by
  ice flow (also called a U-shaped valley).

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Mountains during glaciation
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Mountains after glaciation
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Fjiord - glacially carved valley flooded by the
sea.
Norway
Hudson River
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Glacial Striations - linear glacial scratch marks
on bedrock.
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Glaciers - Agents of Deposition

• Glaciers are highly effective agents of
  deposition.
• Drift - rock debris deposited by glaciers.
• Glacial Lake Deposits - pebble, sand, clay and
  silt sediments accumulated in meltwater lakes.
• Loess - very fine, wind-blown rock flour.

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Till - Nonstratified, poorly sorted drift
deposited directly from glacial ice.
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Stratified drift - sorted, layered sediments
deposited by glacial meltwater - outwash.
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Glaciers - Depositional Landforms

• Ice contact deposits - sediments melted directly
  out from the ice.
• Outwash deposits - sediments deposited by
  meltwater flowing from the ice.

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• Kame - mound of till released by melting ice.

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Esker - serpentine ridge of stratified drift
deposited inside of ice meltwater tunnel.
Esker - Manitoba
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Drumlin - tear-drop-shaped hill created by ice
flow over and around till deposit.
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Drumlins - Manitoba
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Moraine - linear ridge of till deposited at ice
margin.
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Glaciers - Depositional Landforms

• Outwash features - deposition by meltwater in the
  outwash plain (region in front of ice receiving
  flow of meltwater).
• Erratics - boulder size and larger blocks of rock
  deposited by melting glacial ice.

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Landscape during glaciation
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Landscape after glaciation
moraines
Outwash plain in front of moraine.
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Features of a glacial moraine
kame
kettle
outwash
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Ice Caps and Ice Sheets - unconfined by
topography.

• Ice Cap - less than 50,000 km2.
• Ice Sheet - cover major portion of a continent.
• Ice thicker than topography.
• Ice flows in direction of slope of the glacier.
• Greenland and Antarctica - 3000 to 4000 m thick
  (10 - 13 thousand feet or 1.5 to 2 miles!)

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Alpine Glaciers - developed on mountain peaks and
valleys.

• Cirque glacier - small glacier occupying valley
  head.
• Valley glacier - river-like glacial occupying
  valley.
• Piedmont glacier - valley glacier that flows out
  onto the flatlands.
• Fjord glacier - valley glacier with base below
  sea level.
• Ice field - region of interconnected alpine
  glaciers.

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Piedmont Glaciers - lobate lowland glacier fed by
alpine glaciers .