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Glacial Processes and Glacial Processes and Landforms Landforms

Glacial Processes and Landforms

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Glacial Processes and Landforms. Glacial Processes and Landforms. Glaciers’ ability to erode soil and rock, transport sediment, and deposit sediment influenced more than 50 million square kilometers of land surface geomorphically during the last glacial period. Rivers of Ice. Figure 17.1. - PowerPoint PPT Presentation

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Page 1: Glacial Processes and Landforms

Glacial Processes and Glacial Processes and LandformsLandforms

Page 2: Glacial Processes and Landforms

Glacial Processes and Glacial Processes and LandformsLandforms

Glaciers’ ability to erode soil and rock, Glaciers’ ability to erode soil and rock, transport sediment, and deposit sediment transport sediment, and deposit sediment influenced more than 50 million square influenced more than 50 million square kilometers of land surface geomorphically kilometers of land surface geomorphically during the last glacial periodduring the last glacial period

Page 3: Glacial Processes and Landforms

Rivers of IceRivers of Ice

Figure 17.1

Page 4: Glacial Processes and Landforms

VatnajVatnajöökull kull Ice CapIce Cap

Figure 17.5

Page 5: Glacial Processes and Landforms

Patagonian Ice FieldPatagonian Ice Field

Figure 17.5

Page 6: Glacial Processes and Landforms

Greenland’s East CoastGreenland’s East Coast

Figure 17.6

Page 7: Glacial Processes and Landforms

Glacial Processes:Glacial Processes:Growth of GlaciersGrowth of Glaciers

Formation of Glacial IceFormation of Glacial Ice Begins as Begins as snowsnow (density = 50 to 300 kg/m3)(density = 50 to 300 kg/m3)

that can then be modified to icethat can then be modified to ice Neve Neve – snow that has been reduced via partial – snow that has been reduced via partial

meltingmelting and and sublimationsublimation (ablation; (ablation; density = density = >500 kg/m3>500 kg/m3))

FirnFirn – Neve that survives seasonal ablation; – Neve that survives seasonal ablation; may be compacted under later accumulations may be compacted under later accumulations into glacial ice – may take decades or centuriesinto glacial ice – may take decades or centuries

Glacial ice Glacial ice (density = +/- 850 kg/m3)(density = +/- 850 kg/m3) Density of fresh water is +/- 1000 kg/m3Density of fresh water is +/- 1000 kg/m3

Page 8: Glacial Processes and Landforms

Glacier MovementGlacier Movement Not a glacier until it movesNot a glacier until it moves

When snow and ice > +/-20m When snow and ice > +/-20m thickness, ice mass too heavy to thickness, ice mass too heavy to keep rigid shapekeep rigid shape

Begins to flow via plastic deformationBegins to flow via plastic deformation

Page 9: Glacial Processes and Landforms

Glacier Flow RatesGlacier Flow Rates Movement not uniformMovement not uniform

Center and top portions move fasterCenter and top portions move faster

Sides and bottom move slower due Sides and bottom move slower due to frictional drag against valley floor to frictional drag against valley floor and walls.and walls.

Page 10: Glacial Processes and Landforms

Glacier FlowGlacier FlowOverhead view of an alpine valley glacier

showing the relative speed of ice movement

Physical Geography.net

Page 11: Glacial Processes and Landforms

Glacier FlowGlacier Flow

Physical Geography.net

Long cross-section view of an alpine valley glaciershowing the relative speed of ice movement

Page 12: Glacial Processes and Landforms

Glacier FlowGlacier Flow Accumulation in broad, erosional basinAccumulation in broad, erosional basin

Constricted down valley by convergence of Constricted down valley by convergence of narrowing – ice flow compression in narrowing – ice flow compression in central section of the glaciercentral section of the glacier

Flow lines spread out at terminus as ice is Flow lines spread out at terminus as ice is no longer constricted by valley walls. no longer constricted by valley walls. Snout/LobeSnout/Lobe - - swollen tongue of ice at terminus swollen tongue of ice at terminus

due to rapid advancedue to rapid advance

Page 13: Glacial Processes and Landforms

Terminus of Alpine Terminus of Alpine Glaciation Glaciation

Snout/LobeSnout/Lobe - - swollen tongue of ice at swollen tongue of ice at terminus due to rapid advanceterminus due to rapid advance

Merged glaciersMerged glaciers – two or more – can – two or more – can be quite largebe quite large

Page 14: Glacial Processes and Landforms

Glacier FlowGlacier Flow

Physical Geography.net

Typical flow pattern in alpine glacier

Page 15: Glacial Processes and Landforms

Temperate vs.Temperate vs.Cold Climate GlaciersCold Climate Glaciers

Temperate GlaciersTemperate Glaciers Pressure meltingPressure melting may occur despite sub- may occur despite sub-

freezing T’sfreezing T’s May lead to May lead to basal sliding basal sliding May lead to liquified soils beneath glacier May lead to liquified soils beneath glacier Reduced friction = easier, faster Reduced friction = easier, faster

movement (typ. <1m/day but may surge movement (typ. <1m/day but may surge 50 m/day)50 m/day)

Page 16: Glacial Processes and Landforms

Temperate vs.Temperate vs.Cold Climate GlaciersCold Climate Glaciers

Cold Climate GlaciersCold Climate Glaciers

move very slowly - no basal sliding move very slowly - no basal sliding

Movement mainly due to internal Movement mainly due to internal slippage of the ice over the ground slippage of the ice over the ground

Page 17: Glacial Processes and Landforms

Glacier Mass BalanceGlacier Mass BalanceTwo main components:Two main components: AccumulationAccumulation of snow vs. of snow vs. ablationablation of ice of ice

The The Zone of AccumulationZone of Accumulation - upper reaches of - upper reaches of glacierglacier

yearly yearly additionsadditions of snow exceed losses of snow exceed losses (from melting, evaporation, and sublimation)(from melting, evaporation, and sublimation)

Glacier surface covered by snow throughout Glacier surface covered by snow throughout the year in this zone. the year in this zone.

Page 18: Glacial Processes and Landforms

Glacier Mass BalanceGlacier Mass BalanceTwo main components: Two main components: AccumulationAccumulation vs. vs. ablationablation

The The Zone of AblationZone of Ablation - below the zone of - below the zone of accumulationaccumulation

losses of snow and ice from melting, evaporation, losses of snow and ice from melting, evaporation, and sublimation are greater than the additionsand sublimation are greater than the additions

Firn Limit/snow lineFirn Limit/snow line separates these two separates these two zoneszones

Page 19: Glacial Processes and Landforms

Glacier Mass BalanceGlacier Mass Balance

Lag time possible (up to decades) between Lag time possible (up to decades) between accumulation surplus and actual glacial advanceaccumulation surplus and actual glacial advance

Physical Geography.net

Page 20: Glacial Processes and Landforms

Glacier Mass BalanceGlacier Mass Balance

Figure 17.7

Page 21: Glacial Processes and Landforms

Glacier Mass BalanceGlacier Mass Balance

Can experience rapid forward Can experience rapid forward surge (10 (10 to 20 m/day - greater with basal sliding) to 20 m/day - greater with basal sliding) – related to past large snow inputs.– related to past large snow inputs.

Lag time possible (up to decades) Lag time possible (up to decades) between accumulation surplus and between accumulation surplus and actual glacial advanceactual glacial advance

Page 22: Glacial Processes and Landforms

Glacial Ice LossGlacial Ice Loss Due to two processes:Due to two processes:

AblationAblation MeltingMelting EvaporationEvaporation SublimationSublimation

CalvingCalving Occurs when glacier terminus reaches Occurs when glacier terminus reaches

large body of water.large body of water. Portions of the glacier ice break off into Portions of the glacier ice break off into

the water body.the water body. Origin of many icebergs - calving of the Origin of many icebergs - calving of the

Greenland and Antarctic ice Greenland and Antarctic ice sheets/glaciers. sheets/glaciers.

Page 23: Glacial Processes and Landforms

Glacial Ice LossGlacial Ice Loss Gangotri glacier - HimalayasGangotri glacier - Himalayas

Physical Geography.net

Page 24: Glacial Processes and Landforms

Glacial Ice LossGlacial Ice Loss Most glaciers had advanced significantly from the Most glaciers had advanced significantly from the

Middle Ages until around the year 1800, when Middle Ages until around the year 1800, when global temperatures were cooler than present and global temperatures were cooler than present and the northern continents experienced the the northern continents experienced the Little Ice Little Ice Age.Age.

Most glaciers are in retreat due to global warming Most glaciers are in retreat due to global warming of last 1-2 centuries as earth recovered from the of last 1-2 centuries as earth recovered from the Little Ice Age.Little Ice Age.

Mass balances of these glaciers are negative Mass balances of these glaciers are negative because of less snow accumulation or higher because of less snow accumulation or higher ablationablation

Page 25: Glacial Processes and Landforms

Glacial Erosional Glacial Erosional ProcessesProcesses

Two major Two major erosional processes occur processes occur at the base of a glacier:at the base of a glacier:

ScouringScouring

PluckingPlucking

Page 26: Glacial Processes and Landforms

ScouringScouring Rock and sediment, incorporated into Rock and sediment, incorporated into

the moving glacial ice by partial the moving glacial ice by partial melting and refreezing, erodes the melting and refreezing, erodes the bedrock by abrasion.bedrock by abrasion.

Scouring creates a variety of featuresScouring creates a variety of features StriationsStriations Glacial polishGlacial polish Glacial flour/rock flourGlacial flour/rock flour Glacial milkGlacial milk

Page 27: Glacial Processes and Landforms

PluckingPlucking Plucking - Plucking - particle detachment by particle detachment by

moving glacial ice:moving glacial ice: basal ice freezes in rock surface cracks;basal ice freezes in rock surface cracks;

ice pulled and plucked out, detaching rock/soil;ice pulled and plucked out, detaching rock/soil;

greatest on the lee-side (down flow side) of rock greatest on the lee-side (down flow side) of rock mounds, called mounds, called Roche moutonneeRoche moutonnee – longitudinal – longitudinal asymmetry due to asymmetry due to abrasionabrasion on stoss side, on stoss side, pluckingplucking on lee side; on lee side;

Ice extends and spreads apart as it flows over Ice extends and spreads apart as it flows over rock mounds, causing rock mounds, causing crevassescrevasses. .

Page 28: Glacial Processes and Landforms

Glacial Erosional Glacial Erosional ProcessesProcesses

http://www.nature.nps.gov/geology/education/education_graphics.cfm

abrasion

Page 29: Glacial Processes and Landforms

Glacial PolishGlacial Polish

Figure 17.9

Page 30: Glacial Processes and Landforms

Glacial MovementGlacial Movementand Crevassesand Crevasses

Figure 17.8

Page 31: Glacial Processes and Landforms

CrevassesCrevasses

Figure 17.8

Page 32: Glacial Processes and Landforms

CrevassesCrevasses

Figure 17.8

Page 33: Glacial Processes and Landforms

CrevassesCrevasses

Page 34: Glacial Processes and Landforms

CrevassesCrevasses

Page 35: Glacial Processes and Landforms

Glacial LandformsGlacial LandformsTwo types:Two types:

Erosional Erosional

DepositionalDepositional

Page 36: Glacial Processes and Landforms

Erosional Alpine Erosional Alpine LandformsLandforms Merging Glaciers Merging Glaciers – can be quite large– can be quite large

Page 37: Glacial Processes and Landforms

Erosional Alpine Erosional Alpine LandformsLandforms

Erosion exerted on bottoms and sides of alpine valleys - Erosion exerted on bottoms and sides of alpine valleys - guide the flow of glaciersguide the flow of glaciers

TalusTalus – ang. debris-freeze-thaw shattering of bedrock – ang. debris-freeze-thaw shattering of bedrock Talus SlopesTalus Slopes accumulate along valley walls/on glacier accumulate along valley walls/on glacier Bottom and sides of glaciated valley widen and Bottom and sides of glaciated valley widen and

deepen over timedeepen over time Cross-sectional shape changes over time (U-shaped)Cross-sectional shape changes over time (U-shaped) Hanging valleysHanging valleys - small adjoining feeder valleys enter - small adjoining feeder valleys enter

a large valley at some elevation above trunk valley a large valley at some elevation above trunk valley floorfloor May be due to greater erosion by larger, trunk glacierMay be due to greater erosion by larger, trunk glacier May be due to more ice having passed through trunk valleyMay be due to more ice having passed through trunk valley May have spectacular waterfallsMay have spectacular waterfalls

Cliff Caudle, P.G.Environmental Specialist 4

Page 38: Glacial Processes and Landforms

Talus SlopeTalus Slope

Page 39: Glacial Processes and Landforms

Hanging Hanging ValleysValleys

At left: Milford Sound, At left: Milford Sound, South Island, New ZealandSouth Island, New Zealand

Above: Bird Woman Falls, Above: Bird Woman Falls, Glacier National ParkGlacier National Park

Page 40: Glacial Processes and Landforms

Alpine Glacial LandscapeAlpine Glacial Landscape

Figure 17.10

Page 41: Glacial Processes and Landforms

Postglacial LandscapePostglacial Landscape

Figure 17.10

Page 42: Glacial Processes and Landforms

Alpine Erosional FeaturesAlpine Erosional Features

Figure 17.11

Page 43: Glacial Processes and Landforms

Norwegian FjordNorwegian Fjord

Figure 17.12

Page 44: Glacial Processes and Landforms

Glacial DepositionGlacial Deposition

Two major Two major erosional processes add processes add sediment to a glacier:sediment to a glacier:

Abrasion and PluckingAbrasion and Plucking

Mass WastingMass Wasting

Page 45: Glacial Processes and Landforms

Glacial Depositional Glacial Depositional LandformsLandforms

Glacial drift Glacial drift - All glacial deposits including till and outwash - All glacial deposits including till and outwash

TillTill- Heterogeneous, unstratified- Heterogeneous, unstratified- boulders to clay-size- boulders to clay-size

MorainesMorainesDepositional landforms composed of tillDepositional landforms composed of till- End- End- Lateral- Lateral- Medial- Medial

Page 46: Glacial Processes and Landforms

Glacial Depositional Glacial Depositional LandformsLandforms

End MorainesEnd MorainesTerminal moraine Terminal moraine - farthest advance of a - farthest advance of a glacier.glacier.Recessional moraineRecessional moraine – mark halts in – mark halts in retreat of glacierretreat of glacier

Page 47: Glacial Processes and Landforms

Alpine GlacialAlpine GlacialDepositional LandformsDepositional Landforms

End Moraines/terminal morainesEnd Moraines/terminal moraines

Page 48: Glacial Processes and Landforms

Alpine Depositional Alpine Depositional FeaturesFeatures

Figure 17.13

Page 49: Glacial Processes and Landforms

End End MorainesMoraines

End Moraines off End Moraines off the end of Sperry the end of Sperry Glacier, Glacier Glacier, Glacier National ParkNational Park

Page 50: Glacial Processes and Landforms

Alpine GlacialAlpine GlacialDepositional LandformsDepositional Landforms

MorainesMorainesLateral moraineLateral moraine – narrow belt of debris from – narrow belt of debris from

valley side slopes valley side slopes Medial moraine Medial moraine – merging of two lateral – merging of two lateral

morainesmoraines

Page 51: Glacial Processes and Landforms

Alpine GlacialAlpine GlacialDepositional LandformsDepositional Landforms

Lateral and Medial MorainesLateral and Medial Moraines

Page 52: Glacial Processes and Landforms

Glacial Depositional Glacial Depositional LandformsLandforms

Till plainTill plain - large, relatively flat plain of till that forms - large, relatively flat plain of till that forms when detached ice sheet melts in place when detached ice sheet melts in place

ErraticsErratics - Sometimes the sediments in a till plain - Sometimes the sediments in a till plain can contain large boulders. If these boulders are can contain large boulders. If these boulders are transported a great distance from their place of transported a great distance from their place of origin, they are called erraticsorigin, they are called erratics

DrumlinsDrumlins - large, ovoid hills of till shaped by the re- - large, ovoid hills of till shaped by the re-advance of a glacier over previously deposited advance of a glacier over previously deposited ground moraine.ground moraine.

Page 53: Glacial Processes and Landforms

Continental Glaciation Continental Glaciation Erosional LandformsErosional Landforms

-Widespread -Widespread abrasion and gougingabrasion and gouging-Widespread glacial polish and striations-Widespread glacial polish and striations-Huge U-shaped valleys from previously -Huge U-shaped valleys from previously

V-shaped stream valleysV-shaped stream valleys-Large basins scooped out, many with -Large basins scooped out, many with

large lakes in them today (i.e., Great large lakes in them today (i.e., Great Lakes) Lakes)

Page 54: Glacial Processes and Landforms

Glacial ErosionGlacial Erosion

http://www.nature.nps.gov/geology/education/education_graphics.cfm

Page 55: Glacial Processes and Landforms

Glacial FlowGlacial Flow WhalebackWhaleback

Page 56: Glacial Processes and Landforms

Glacial PolishGlacial Polish

Figure 17.9

Page 57: Glacial Processes and Landforms

Continental Glacial Continental Glacial Depositional LandformsDepositional Landforms

Till plainTill plain - large, relatively flat plain of till that - large, relatively flat plain of till that forms when detached ice sheet melts in place forms when detached ice sheet melts in place

ErraticsErratics - Sometimes the sediments in a till plain - Sometimes the sediments in a till plain can contain large boulders. If these boulders are can contain large boulders. If these boulders are transported a great distance from their place of transported a great distance from their place of origin, they are called erraticsorigin, they are called erratics

DrumlinsDrumlins - large, ovoid hills of till shaped by the - large, ovoid hills of till shaped by the re-advance of a glacier over previously re-advance of a glacier over previously deposited ground moraine.deposited ground moraine.

Page 58: Glacial Processes and Landforms

Continental Continental Glacier Glacier Depositional Depositional

FeaturesFeatures

Figure 17.15

Page 59: Glacial Processes and Landforms

Till Till PlainsPlains

Left: Northwest Territories, Lac Left: Northwest Territories, Lac de Gras, Canada – Geological de Gras, Canada – Geological Survey of Canada. Note Survey of Canada. Note Erratics.Erratics.

Above: Till Plain, Region Above: Till Plain, Region Unknown, from University of Unknown, from University of California – Santa Barbara California – Santa Barbara Photo Collection. Note Braided Photo Collection. Note Braided Meltwater Channels.Meltwater Channels.

Page 60: Glacial Processes and Landforms

http://www.nature.nps.gov/geology/education/education_graphics.cfm

Page 61: Glacial Processes and Landforms

Drumlin SwarmDrumlin Swarm

Figure 17.17

Page 62: Glacial Processes and Landforms

Glacial Depositional Glacial Depositional LandformsLandforms

DrumlinsDrumlins

Page 63: Glacial Processes and Landforms

Glacial Depositional Glacial Depositional LandformsLandforms

ErraticsErratics

Page 64: Glacial Processes and Landforms

Glacial Depositional Glacial Depositional LandformsLandforms

Glacial driftGlacial driftAll sediments that are carried and deposited by All sediments that are carried and deposited by

glaciersglaciers

Most debris added to a glacier arrives at the snout Most debris added to a glacier arrives at the snout either through either through - continual forward flow of glacial ice, deposited - continual forward flow of glacial ice, deposited as till, oras till, or

- through - through meltwatermeltwater, as , as glaciofluvial depositsglaciofluvial deposits. .

Page 65: Glacial Processes and Landforms

Glacial Depositional Glacial Depositional LandformsLandforms

Glaciofluvial depositsGlaciofluvial deposits - stratified and less well sorted.- stratified and less well sorted.

Outwash depositsOutwash deposits- deposited where there are a great - deposited where there are a great number of meltwater streams number of meltwater streams depositing material ahead of the glacier. depositing material ahead of the glacier.

Page 66: Glacial Processes and Landforms

Glacial Depositional Glacial Depositional LandformsLandforms

Glaciofluvial LandformsGlaciofluvial LandformsKameKame - conical-shaped pile of sand - conical-shaped pile of sand and gravel formed where sediment-and gravel formed where sediment-rich water flows into a crevasse or rich water flows into a crevasse or depression in the icedepression in the ice EskerEsker – sand and gravel deposited – sand and gravel deposited by meltwater flowing under glacierby meltwater flowing under glacierKettles Kettles - -

Page 67: Glacial Processes and Landforms

Glacial Depositional Glacial Depositional LandformsLandforms

Glaciofluvial deposits/Outwash depositsGlaciofluvial deposits/Outwash deposits

Page 68: Glacial Processes and Landforms

Glacial Depositional Glacial Depositional LandformsLandforms

Glaciofluvial Landforms: KameGlaciofluvial Landforms: Kame

Page 69: Glacial Processes and Landforms

Glacial Depositional Glacial Depositional LandformsLandforms

Glaciofluvial Landforms: EskerGlaciofluvial Landforms: Esker

Page 70: Glacial Processes and Landforms

Glacial Depositional Glacial Depositional LandformsLandforms

Glaciofluvial Landforms: KettlesGlaciofluvial Landforms: Kettles