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Chapter 19: Glacial Systems and Landforms
Physical Physical GeographyGeographyNinth EditionNinth Edition
Robert E. Gabler
James. F. Petersen
L. Michael Trapasso
Dorothy Sack
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Glacial Systems and Landforms
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Glacial Systems and Landforms
• Glaciers– Large masses of flowing ice– Glacier’s role
• Climate indicator’s• Long-term storage of fresh water as ice• Hydrologic cycle
– Process of erosion, transportation, and deposition by glaciers leaves a distinctive mark
– Locations:• Alps, Rocky Mountains, Himalayas, Andes
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19.1 Glacier Formation and the Hydrologic Cycle
• Glaciers– Masses of flowing ice that
have accumulated on land– Annual input of frozen
precipitation exceeded yearly loss by melting and other processes
– Snowflakes• Compaction, melting and
refreezing• Firn
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19.1 Glacier Formation and the Hydrologic Cycle
• Glaciers– Open systems with:
• Input• Storage• Output
– Accumulation– Ablation– Sublimation– Calving– Icebergs
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19.1 Glacier Formation and the Hydrologic Cycle
• Glaciers– Controlled by 2 basic
climatic conditions:• Precipitation• Freezing temperatures
– 2.25% of Earth’s total water
– 70% of Earth’s fresh water
– Moves slowly with tremendous energy
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19.2 Types of Glaciers
• Two Major categories– Alpine– Continental
• Alpine (High elevation)– Fed by ice and snow in
mountain areas– Usually occupy
preexisting valleys– Valley glaciers
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19.2 Types of Glaciers
• Alpine (High elevation)– Piedmont glaciers
• Ice flows beyond the valley, spreading out over flatter land
– Cirque glaciers• Smallest type
– Locations:• Rockies, Sierra Nevada,
Cascades, Olympic, Coast Range
• Andes, Himalaya, Mount Kenya and Kilimanjaro
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19.2 Types of Glaciers
• Continental glaciers– Much larger and thicker– High latitude– 2 polar ice sheets
• Greenland
• Antarctica
– Ice capsQ: How is radial ice flow both
similar to and different from the radial drainage pattern observed for some stream systems?
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19.3 How do Glaciers flow?
• Movement Processes– Internal plastic
deformation• Weight of overlying ice,
firn, and snow causes ice crystals at depth to arrange themselves in parallel layers that glide over each other
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19.3 How do Glaciers flow?
• Movement Processes– Processes at base
• Basal sliding– Processes at top
• Brittle ice• Fractures and cracks• Crevasses• Icefalls
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19.4 Glaciers as Geomorphic Agents
• Glaciers remove and entrain rock particles by 2 erosion processes– Plucking
• Moving ice freezes onto loosened rocks, incorporating them into the flow
– Abrasion
Q: How does sediment load of a glacier differ from sediment load of a stream?
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19.5 Alpine Glaciers
• Zone of accumulation (input)• Zone of ablation (ablation exceeds accumulation)
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19.5 Alpine Glaciers
• Equilibrium line (boundary)
Q: What additional information would be needed to assess if the boundary between the white and blue zones on this photo is the glacier’s annual equilibrium line?
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19.5 Alpine Glaciers
• Factors influencing Equilibrium line– Latitude– Elevation– Temperature– Amount of insolation– Mountain slope– Wind
Q: Do any slope characteristics vary by aspect in the region where you live?
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19.5 Alpine Glaciers
• Glacier’s head– Cirque headwall– Bergschrund
• Terminus
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19.5 Alpine Glaciers
• Equilibrium and the Glacial Budget– Changes throughout year– Growing or shrinking:
• Observe terminus• Advance (further down
valley)• Retreat• Most receding since 1890
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19.5 Alpine Glaciers
• Erosional Landforms of Alpine Glaciation– Striations
• Linear scratches, grooves, and gouges
• Direction of ice flow
Q: Can the direction of ice flow be determined with certainty from the evidence in this photograph?
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19.5 Alpine Glaciers
• Erosional Landforms of Alpine Glaciation– Roches moutonnées
• Asymmetric bedrock hills or knobs
• Smoothly rounded on the up-side by abrasion
• Plucking on down-ice side
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19.5 Alpine Glaciers
• Erosional Landforms of Alpine Glaciation– Cirque
• Bowls• Cirque lakes
– Arête• Jagged sawtooth-
shaped spine of rock
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19.5 Alpine Glaciers
• Erosional Landforms of Alpine Glaciation– Horn
• 3 or more cirques meet• Pyramid shape• Matterhorn
– Col• Pass formed by
headward erosion of 2 cirques
– Glacial trough
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19.5 Alpine Glaciers
• Erosional Landforms of Alpine Glaciation– Paternoster lakes
• Glacier creates rock steps and excavated basins
• This forms Lake chains
– Fjord• Abandoned glacial
trough that use to extend down to ocean
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19.5 Alpine Glaciers
• Erosional Landforms of Alpine Glaciation– Hanging Valleys
• Waterfall• Yosemite Valley, CA
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19.5 Alpine Glaciers
• Depositional Landforms of Alpine Glaciation– Glaciofluvial– Drift– Moraines– Lateral moraines
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19.5 Alpine Glaciers
• Depositional Landforms of Alpine Glaciation– Medial moraine– End moraine– Terminal moraine– Recessional moraine– Ground moraine– Glacial outwash
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19.6 Continental Glaciers
• Ice sheets & Ice caps– Convex lens cross
section– Thick in center and
thinning toward edges
Q: How is this manner of ice flow difference from and similar to that of a valley glacier?
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19.6 Continental Glaciers
• Existing Continental Glaciers– Cover about 10% of
Earth– Locations: Iceland,
arctic islands, Greenland ice sheet, and Antarctic Ice Sheet
– Outlet glaciers
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19.6 Continental Glaciers
• Existing Continental Glaciers– Antarctic Ice Sheet
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19.6 Continental Glaciers
• Existing Continental Glaciers– Antarctic Ice Sheet– Ice sheet
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19.6 Continental Glaciers
• Pleistocene Glaciation– Began 2.4 mya and ended 10,000 years ago– Maximum extent: ice covered 1/3 of Earth– Interglacial– Sea level changes
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19.6 Continental Glaciers
• Continental Glaciers and Erosional Landforms– Ice scoured plains
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19.6 Continental Glaciers
• Continental Glaciers and Depositional Landforms– End Moraines– Till Plains– Outwash Plains– Drumlins– Eskers– Kames– Erratics
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19.6 Continental Glaciers
• End Moraines
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19.6 Continental Glaciers
• Till Plains
• Outwash Plains– Kettles– Kettle lakes
• Drumlin
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19.6 Continental Glaciers
• Esker
• Kames– Kame terraces
• Erratics
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19.7 Glacial Lakes
• Pleistocene ice sheets created numerous lake basins– Finger Lakes, NY– Great lakes, US– Lake Chelan, WA– Ice-marginal lakes
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19.7 Glacial Lakes
• Lake Missoula– Scablands– Dry waterfalls
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19.7 Glacial Lakes
• Great Lakes– World’s largest lake system
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19.8 Periglacial Landscapes
• Periglacial environments– High latitudes of N.
hemisphere– Lacking year round ice or
snow undergoing intense frost action
– Frost action• Freezing/thawing of soil• Frost heave and thaw
settlement
– Patterned ground
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19.8 Periglacial Landscapes
• Permafrost– Solifluction– Ice wedge polygons– Construction Techniques
• Build above ground
– Climate Change and permafrost
• Thermokarst development• Release of Carbon Dioxide
and Methane
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Physical Geography
End of Chapter 19: Glacial Systems and Landforms