Glaciers and
Glacial Landforms
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.
Ice movement in a glacier
Snow falls
Ice melts
eroded boulders
Zone of accumulation
Zone of wasting
Ice movement in a glacier
Snow falls
compacts to ice
Ice melts
Zone of accumulation
Zone of wasting
Ice movement in a glacier
• If rate of accumulation is greater than melting, glacier will advance.
Snow falls
compacts to ice
Glacier advances
Ice melts
Flowing ice carves the landscape
Zone of accumulation
Zone of wasting
Ice movement in a glacier
• When rate of melting equals rate of accumulation, glacier stops advancing.
• Equilibrium
Snow falls
Glacier stops advancing.
Ice melts
Zone of accumulation
Zone of wasting
Ice movement in a glacier
• in equilibrium, glacier does not appear to change position.
• ice is always in motion.
• ice accumulation equals ice melting.
Snow falls
Glacier acts like a conveyor belt, eroding
and carrying rock, sediments, and soil to
its terminus.
terminus
Zone of accumulation
Zone of wasting
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.
Snow falls
Melting ice deposits rock and sediment.
Glacial deposits create distinctive
landforms.
Glacier retreats
Zone of accumulation
moraine
Zone of wasting
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.
Snow falls
Melting ice deposits rock and sediment.
Glacial deposits create distinctive
landforms.
Glacier retreats
Zone of accumulation
moraine
Zone of wasting
Zone of ablation (wastage)
(more melting than snowfall)
Zone of accumulation
(more snow falls then melts per year)
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.
Glaciers - Erosional Landforms
• Cirque - semicircular hollow with steep headwall carved
by glaciers into an alpine valley head.
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.
Glaciers - Erosional Landforms
• Glacial trough - wide, parabolic valley carved by ice
flow (also called a “U-shaped” valley).
Mountains during glaciation
Mountains after glaciation
Fjiord - glacially carved valley flooded by the sea.
Norway
Hudson River
Glacial Striations - linear glacial scratch marks on bedrock.
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.
Till - Nonstratified, poorly sorted drift deposited
directly from glacial ice.
Stratified drift - sorted, layered sediments deposited
by glacial meltwater - outwash.
Glaciers - Depositional Landforms
• Ice contact deposits - sediments melted directly out from
the ice.
• Outwash deposits - sediments deposited by meltwater
flowing from the ice.
Kame - mound of till released by melting ice.
Esker - serpentine ridge of stratified drift deposited
inside of ice meltwater tunnel.
Esker - Manitoba
Drumlin - tear-drop-shaped hill created by ice flow over
and around till deposit.
Drumlins - Manitoba
Moraine - linear ridge of till deposited at ice margin.
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.
Landscape during glaciation
Kettles - depressions formed as stranded ice blocks melt in outwash.
Landscape after glaciation
Kettles - depressions formed as stranded ice blocks melt in outwash.
moraines
Outwash plain in front of moraine.
Features of a glacial moraine
kame
kettle
outwash
Ice Caps and Ice Sheets - unconfined by
topography.
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•
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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!)
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.
Piedmont Glaciers - lobate lowland
glacier fed by alpine glaciers .