Chapter 12: Glaciers

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Chapter 12 Glaciers glaciation
Today
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1) Types of glaciers
GLACIERS
...definition

• A Glacier is
• part of hydrological cycle
• thick ice mass
• formed on land
• made by snow
• accumulation
• compaction
• recrystallization
• able to flow

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GLACIERS
...definition

• A Glacier is
• part of hydrological cycle
• thick ice mass
• formed on land
• made by snow
• accumulation
• compaction
• recrystallization
• able to flow

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1) Types of glaciers
GLACIERS

• Valley (or Alpine) glaciers
• Ice sheets
• Ice caps
• Outlet glaciers
• Piedmont glaciers

• mountainous regions
• occupy old stream valleys
• length greater than width

St. Marys Lake, Glaciar National Park, Montana
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1) Types of glaciers
GLACIERS

• Valley (or Alpine) glaciers
• Ice sheets
• Ice caps
• Outlet glaciers
• Piedmont glaciers

• mountainous regions
• occupy old stream valleys
• length greater than width

• large scale feature
• Greenland, Antarctica
• continental ice sheets
• ice shelves _at_ coasts

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1) Types of glaciers
GLACIERS

• Valley (or Alpine) glaciers
• Ice sheets
• Ice caps
• Outlet glaciers
• Piedmont glaciers

Iceland

• mountainous regions
• occupy old stream valleys
• length greater than width

• large scale feature
• Greenland, Antarctica
• continental ice sheets
• ice shelves _at_ coasts

• ice cover of plateaus
• smaller than ice sheets
• e.g., Iceland

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1) Types of glaciers
GLACIERS
GLACIERS

• Valley (or Alpine) glaciers
• Ice sheets
• Ice caps
• Outlet glaciers
• Piedmont glaciers

• mountainous regions
• occupy old stream valleys
• length greater than width

• large scale feature
• Greenland, Antarctica
• continental ice sheets
• ice shelves _at_ coasts

• ice cover of plateaus
• smaller than ice sheets
• e.g., Iceland

• fed by ice sheets caps
• essentially valley glaciers
• flow to sea

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1) Types of glaciers
GLACIERS
GLACIERS

• Valley (or Alpine) glaciers
• Ice sheets
• Ice caps
• Outlet glaciers
• Piedmont glaciers

• mountainous regions
• occupy old stream valleys
• length greater than width

• large scale feature
• Greenland, Antarctica
• continental ice sheets
• ice shelves _at_ coasts

• ice cover of plateaus
• smaller than ice sheets
• e.g., Iceland

• fed by ice sheets caps
• essentially valley glaciers
• flow to sea

• at base of steep mountains
• fed by valley glaciers
• variable size

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2) Glacier formation/movement
GLACIERS
Glacial ice raw material
Snow
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2) Glacier formation/movement
GLACIERS

• Plastic flow
• Basal slip

Movement within the ice
Entire ice mass slips along ground
Zone of fracture above 50 m
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2) Glacier formation/movement
GLACIERS
Rates of flow

• fastest in center of glacier
• 100s m per year forward motion
• surges

Frictional drag along sides slows down edges
Quite varable
Periods of rapid flow
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2) Glacier formation/movement
GLACIERS

• glacier budget
• snowline
• zone of wastage
• calving

Balance between accumulation at upper end loss
(ablation) at lower end
Lower limit of zone of accumulation
Net loss (melting)
Large ice pieces break off
.23 years later
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2) Glacier formation/movement
GLACIERS

• glacier budget
• snowline
• zone of wastage
• calving

Balance between accumulation at upper end loss
(ablation) at lower end
Lower limit of zone of accumulation
Net loss (melting)
Large ice pieces break off
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2) Glacier formation/movement
GLACIERS

• glacier budget
• snowline
• zone of wastage
• calving

Balance between accumulation at upper end loss
(ablation) at lower end
Lower limit of zone of accumulation
Net loss (melting)
Large ice pieces break off
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3) Glacial erosion
GLACIERS
2 ways
plucking - glacier loosens/lifts/incorporates
fractured rock
erratics
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3) Glacial erosion
GLACIERS
2 ways
plucking - glacier loosens/lifts/incorporates
fractured rock abrasion - glacierrock fragments
scrape over bedrock (like
sandpaper), make rock flour
scrape marks on bedrock glacial striations

give direction of flow
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3) Glacial erosion
GLACIERS
Rate of erosion

• glacier speed
• ice thickness
• shape, abundance,hardness of acquired rock
  fragments
• erodibility of underlying bedrock

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4) Glacial landforms deposits
GLACIERS
glacial trough U-shaped (from V-shaped) truncated
spurs ice chops off tips, leaves triangular
cliffs hanging valleys main glaciers cut deeper
than side feeds cirques bowl-shaped depressions
at tops of U valleys tarn small lake in cirque
depression fiord steep-sided inlets to sea
Valleys
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4) Glacial landforms deposits
GLACIERS
Aretes
Sharp-edged ridges (close cirques, or
parallel valleys)
Horns
Peaks left over after cirques enlarged
Matterhorn
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4) Glacial landforms deposits
GLACIERS

• dropped when ice melts
• 10-100s m thick
• glacial drift - sediments of
• glacial origin

deposits
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4) Glacial landforms deposits
GLACIERS

• Moraines

Till landforms
end moraine ridge of till at end of stable
glacier terminal moraine outermost end
moraine recessional moraine all other end
moraines ground moraine from retreating
glacier lateral moraine debris on side of
glacier medial moraine from 2 glaciers joining
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4) Glacial landforms deposits
GLACIERS

• Drumlins

Till landforms
Smooth elongated parallel hills
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4) Glacial landforms deposits
GLACIERS

• outwash plains
• kettle lakes
• eskers

Stratified drift landforms
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GLACIERS
5) Side-effects
Ice retreat/advances
some animal/plant migration forced some
extinctions
Stream flow changes Post-glacial uplift Sea
level changes
Pluvial lakes
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GLACIERS
5) Side-effects
Ice retreat/advances
some animal/plant migration forced some
extinctions
Stream flow changes Post-glacial uplift Sea
level changes
Pluvial lakes
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6) Ice age causes
GLACIERS

• Older Ice Ages

2 billion years ago 600 million years ago 250
million years ago
Evidence from tillites plate
tectonics
lithified glacial till
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6) Ice age causes
GLACIERS

• Earth orbit variations

Shape of orbit (more elliptical) changes in tilt
of rotation axis wobbling of axis
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Other planets!
GLACIERS

• Other Solar system objects have ice

Europa (A Jupiter moon)
Mars
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Other planets!
GLACIERS