Chapter 19: Glacial Systems and Landforms

Physical Physical GeographyGeographyNinth EditionNinth Edition

Robert E. Gabler

James. F. Petersen

L. Michael Trapasso

Dorothy Sack

Glacial Systems and Landforms

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

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

19.1 Glacier Formation and the Hydrologic Cycle

• Glaciers– Open systems with:

• Input• Storage• Output

– Accumulation– Ablation– Sublimation– Calving– Icebergs

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

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

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

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?

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

19.3 How do Glaciers flow?

• Movement Processes– Processes at base

• Basal sliding– Processes at top

• Brittle ice• Fractures and cracks• Crevasses• Icefalls

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?

19.5 Alpine Glaciers

• Zone of accumulation (input)• Zone of ablation (ablation exceeds accumulation)

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?

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?

19.5 Alpine Glaciers

• Glacier’s head– Cirque headwall– Bergschrund

• Terminus

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

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?

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

19.5 Alpine Glaciers

• Erosional Landforms of Alpine Glaciation– Cirque

• Bowls• Cirque lakes

– Arête• Jagged sawtooth-

shaped spine of rock

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

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

19.5 Alpine Glaciers

• Erosional Landforms of Alpine Glaciation– Hanging Valleys

• Waterfall• Yosemite Valley, CA

19.5 Alpine Glaciers

• Depositional Landforms of Alpine Glaciation– Glaciofluvial– Drift– Moraines– Lateral moraines

19.5 Alpine Glaciers

• Depositional Landforms of Alpine Glaciation– Medial moraine– End moraine– Terminal moraine– Recessional moraine– Ground moraine– Glacial outwash

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?

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

19.6 Continental Glaciers

• Existing Continental Glaciers– Antarctic Ice Sheet

19.6 Continental Glaciers

• Existing Continental Glaciers– Antarctic Ice Sheet– Ice sheet

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

19.6 Continental Glaciers

• Continental Glaciers and Erosional Landforms– Ice scoured plains

19.6 Continental Glaciers

• Continental Glaciers and Depositional Landforms– End Moraines– Till Plains– Outwash Plains– Drumlins– Eskers– Kames– Erratics

19.6 Continental Glaciers

• End Moraines

19.6 Continental Glaciers

• Till Plains

• Outwash Plains– Kettles– Kettle lakes

• Drumlin

19.6 Continental Glaciers

• Esker

• Kames– Kame terraces

• Erratics

19.7 Glacial Lakes

• Pleistocene ice sheets created numerous lake basins– Finger Lakes, NY– Great lakes, US– Lake Chelan, WA– Ice-marginal lakes

19.7 Glacial Lakes

• Lake Missoula– Scablands– Dry waterfalls

19.7 Glacial Lakes

• Great Lakes– World’s largest lake system

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

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

Physical Geography

End of Chapter 19: Glacial Systems and Landforms